=encoding utf8

=head1 名前

guestfs - 仮想マシンイメージのアクセスまたは変更のためのライブラリ

=head1 書式

#include <guestfs.h>
 guestfs_h *g = guestfs_create ();
 guestfs_add_drive (g, "guest.img");
 guestfs_launch (g);
 guestfs_mount (g, "/dev/sda1", "/");
 guestfs_touch (g, "/hello");
 guestfs_umount (g, "/");
 guestfs_close (g);

 cc prog.c -o prog -lguestfs
or:
 cc prog.c -o prog `pkg-config libguestfs --cflags --libs`

=head1 説明

Libguestfs is a library for accessing and modifying disk images and virtual
machines.  This manual page documents the C API.

If you are looking for an introduction to libguestfs, see the web site:
L<http://libguestfs.org/>

Each virt tool has its own man page (for a full list, go to L</SEE ALSO> at
the end of this file).

The libguestfs FAQ contains many useful answers: L<guestfs-faq(1)>.

For examples of using the API from C, see L<guestfs-examples(3)>.  For
examples in other languages, see L</USING LIBGUESTFS WITH OTHER PROGRAMMING
LANGUAGES> below.

=head1 API 概要

このセクションは libguestfs API の簡単な概要を示します。  一緒に呼ばれるグループ API
を試みます。これは、このマニュアルのメインセクションにおいて個々の呼び出しに関して読む必要が無くなります。

=head2 ハンドル

libguestfs 呼び出しを使用する前に、ハンドルを作成する必要があります。そして、少なくとも 1
つのディスクイメージをハンドルを追加する必要があります。続けて、ハンドルを開始して、好きな操作を実行します。最後に、ハンドルを閉じます。利便性のため、ハンドル変数の名前を
1 文字の C<g> を使用します。もちろん、好きな名前を使うことができます。

libguestfs を使用しているすべてのプログラムの一般的な構造はこのようなものです:

 guestfs_h *g = guestfs_create ();
 
 /* 複数のディスクイメージがあれば、その回数だけ
  * guestfs_add_drive を呼び出します。
  */
 guestfs_add_drive (g, "guest.img");
 
 /* 大抵の操作呼び出しはハンドル 'g' を開始するまでうまく
  * 機能しません。ドライブを追加した「後」、他のコマンド
  * を実行する「前」にこれを行う必要があります。
  */
 guestfs_launch (g);
 
 /* どのパーティションや論理ボリュームが利用できるかを確認できます。
  */
 char **partitions = guestfs_list_partitions (g);
 char **logvols = guestfs_lvs (g);
 
 /* イメージにあるファイルシステムにアクセスするには、
  * マウントしなければいけません。
  */
 guestfs_mount (g, "/dev/sda1", "/");
 
 /* これで、仮想マシンのイメージにおいて、ファイルシステムの
  * アクションを実行できます。
  */
 guestfs_touch (g, "/hello");
 
 /* これは libguestfs < 1.5.24 に対してのみ必要にです。
  * それ以降はハンドルを閉じるときに自動的に実行されます。
  * このページにある自動同期の議論を参照してください。
  */
 guestfs_sync (g);
 
 /* 'g' を閉じます。 */
 guestfs_close (g);

上のコードは何もエラーチェックを含めていません。実際のコードにおいては、エラーに対して返り値を注意深く確認すべきです。一般的に、整数を返すすべての関数はエラーのときに
C<-1> を返します。ポインターを返すすべての関数はエラーのときに C<NULL> を返します。エラーを処理する方法については以下のセクション
L</エラー処理方法>
を参照してください。各関数がどのようにエラー表示を返すのかを詳しく確認するには、以下にある各関数のドキュメントを参照してください。全体的に動作する例は
L<guestfs-examples(3)> を参照してください。

=head2 ディスクイメージ

イメージファイル名 (上の例では C<"guest.img">) は、仮想マシンのディスクイメージ、物理ハードディスクの L<dd(1)>
コピー、実際のブロックデバイス、単に L<posix_fallocate(3)> から作成した 0 の空ファイルがありえます。libguestfs
はこれらすべてに役に立つことをさせます。

近代的なコードにおいてドライブを追加するために使用する呼び出しは L</guestfs_add_drive_opts> です。書き込み許可、raw
形式指定にて、ディスクイメージを追加するには、次を実行します:

 guestfs_add_drive_opts (g, filename,
                         GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw",
                         -1);

以下を使用して、読み込み専用のディスクを追加できます:

 guestfs_add_drive_opts (g, filename,
                         GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw",
                         GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
                         -1);

または、古い関数 L</guestfs_add_drive_ro> を呼び出すことによりできます。どちらの場合も libguestfs
はファイルを変更できません。

ディスクイメージが使用中ならば、たとえば仮想マシンにより使用されているならば、特に注意してください。読み書き可能で追加することにより、ほぼ確実にディスク破損を引き起こします。一方、読み込み専用で追加することは安全です。

少なくとも 1 つのディスクイメージを追加する必要があります。複数のディスクイメージを追加することもできます。 API において、ディスクイメージは通常
C</dev/sda> （最初に追加したもの）、C</dev/sdb> （2 番目に追加したもの）などのように参照されます。

一度 L</guestfs_launch>
が呼び出されると、これ以上イメージを追加することはできません。それらを追加するためには、デバイス名の一覧を取得するために
L</guestfs_list_devices> を呼び出せます。以下の L</ブロックデバイス命名法> を参照してください。

=head2 マウント

ファイルシステムを含むディスクイメージにおいて、ファイルを読み込みまたは書き込みできる、ディレクトリーを作成できるなどの前に、
L</guestfs_mount_options> または L</guestfs_mount_ro>
を使用してそれらのファイルシステムをマウントする必要があります。ディスクイメージが（たとえば）そのパーティションにおいてファイルシステムを持つ 1
つのパーティションを含むことをすでにわかっているならば、それを直接マウントできます:

 guestfs_mount_options (g, "", "/dev/sda1", "/");

ここで C</dev/sda1> は文字どおり追加した最初のディスクイメージ (C</dev/sda>) の最初のパーティション (C<1>)
を意味します。ディスクが Linux LVM2 論理ボリュームを含んでいると、代わりにそれら (例: C</dev/VG/LV>)
を参照できます。これらは libguestfs 仮想デバイスであり、ホストデバイスには何もしないことに注意してください。

ディスクイメージを与えられていますが、何が含まれているかわからないならば、理解する必要があります。 libguestfs はそれもできます:
利用可能なパーティションおよび論理ボリュームを一覧表示するために L</guestfs_list_partitions> および
L</guestfs_lvs> を使用します。そして、マウント可能なものを確認するためにそれぞれマウントを試します。もしくは
L</guestfs_vfs_type> または L</guestfs_file> を用いて検査します。単にファイルシステムを一覧表示するには
L</guestfs_list_filesystems> を使用します。

libguestfs は未知のディスクイメージの検査のための API セットもあります（以下の L</INSPECTION> 参照）。しかし、
libguestfs の上に構築されたプログラム、とくに L<virt-inspector(1)> は、より簡単に見ることができます。

ファイルシステムを読み込み専用でマウントするには L</guestfs_mount_ro> を使用します。いくつかの他の変種
C<guestfs_mount_*> 呼び出しがあります。

=head2 ファイルシステムのアクセスおよび変更

libguestfs API
の大半は、マウントされたファイルシステムにあるファイル、ディレクトリー、シンボリックリンクなどを参照および変更するためのかなり低レベルな関数呼び出しから構成されます。このマニュアルページにおいて以下に詳細に一覧化されている、そのような呼び出しは
100 以上あります。この概要においてすべてを取り扱うことは考えていません。

C<"/"> から始まり、マウントポイントを含む完全パスとしてファイル名を指定します。

たとえば、C<"/"> にファイルシステムをマウントして、C<"etc/passwd"> というファイルを読み込みたければ、次のようにできます:

 char *data = guestfs_cat (g, "/etc/passwd");

これは、ファイルの完全な内容を含む（いくつかの条件とともに: 以下の L</ダウンロード> 参照）新しく割り当てられたバッファーとして C<data>
を返します。もしくは、エラーがあれば C<NULL> を返します。

もう 1 つの例として、ファイルシステムに C<"var"> という名前の最上位ディレクトリーを作成するには、次のようにします:

 guestfs_mkdir (g, "/var");

シンボリックリンクを作成するには次のようにできます:

 guestfs_ln_s (g, "/etc/init.d/portmap",
               "/etc/rc3.d/S30portmap");

libguestfs は相対パスの使用を拒否します。現在の作業ディレクトリーという概念がありません。

libguestfs
は多くの状況においてエラーを返します。たとえば、ファイルシステムが書き込みできない場合です。または、要求したファイルやディレクトリーが存在しない場合です。
C API (ここにドキュメント化されています)
を使用しているならば、各呼び出しの後でそれらのエラー条件を確認する必要があります。（他の言語バインドは、これらのエラーを例外の中に含めてください。）

ファイルの書き込みはハンドルごとの umask により影響されます。L</guestfs_umask> を呼び出すことにより設定され、初期値は 022
です。 L</UMASK> 参照。

Since libguestfs 1.18, it is possible to mount the libguestfs filesystem on
a local directory, subject to some restrictions.  See L</MOUNT LOCAL> below.

=head2 パーティション

libguestfs はディスクイメージにあるパーティションテーブルを読み込み、作成、変更するための API 呼び出しがあります。

ディスク全体に単一のパーティションを作成したいという一般的な場合、 L</guestfs_part_disk> 呼び出しを使用できます:

 const char *parttype = "mbr";
 if (disk_is_larger_than_2TB)
   parttype = "gpt";
 guestfs_part_disk (g, "/dev/sda", parttype);

以前ディスクイメージにあったものを明示的にすべて効果的に完全消去します。

=head2 LVM2

libguestfs は L</guestfs_lvcreate> および L</guestfs_vgremove> のような、大部分の LVM2
API にアクセスできます。物理ボリューム、ボリュームグループ、論理ボリュームの概念になじみがなければ、役に立たないかもしれません。

この著者はオンラインで L<http://tldp.org/HOWTO/LVM-HOWTO/> にある  LVM HOWTO
を読むことを強く推奨します。

=head2 ダウンロード

小さなテキストのみのファイルをダウンロードするには L</guestfs_cat> を使用します。この呼び出しは 2 MB 未満かつ ASCII
NULL (C<\0>) 文字を含まないファイルに制限されます。しかしながら、API は非常に簡単に使用できます。

L</guestfs_read_file> は、（ポインター、容量）の組を返すので、任意の 8
ビットデータを含むファイルを読み込むために使用できます。しかしながら、今のところ 2 MB 未満の「小さな」ファイルに制限されています。

L</guestfs_download> 内容やファイルサイズに制限はありません (例えば、4 GB 以上のファイルでも可能)
任意のファイルをダウンロードするために使用することができます。

複数のファイルをダウンロードするには L</guestfs_tar_out> および L</guestfs_tgz_out> を参照してください。

=head2 アップロード方法

頻繁にディスクイメージへのファイルを書き込みたいという場合です。

固定的な内容を持つ小さなファイルを書き込むには、L</guestfs_write> を使用します。すべて 0
のファイルを作成するには、L</guestfs_truncate_size> (スパース) または L</guestfs_fallocate64>
(すべてのブロックを割り当て済み) を使用します。テストファイルを作成するためのさまざまな他の関数があります。たとえば、
L</guestfs_fill> や L</guestfs_fill_pattern> があります。

単一のファイルをアップロードするには、L</guestfs_upload> を使用します。この呼び出しは、ファイルの内容や容量（4 GB
より大きいファイルさえ）における制限がありません。

複数のファイルをアップロードするには、L</guestfs_tar_in> および L</guestfs_tgz_in> を参照してください。

However the fastest way to upload I<large numbers of arbitrary files> is to
turn them into a squashfs or CD ISO (see L<mksquashfs(8)> and
L<mkisofs(8)>), then attach this using L</guestfs_add_drive_ro>.  If you add
the drive in a predictable way (eg. adding it last after all other drives)
then you can get the device name from L</guestfs_list_devices> and mount it
directly using L</guestfs_mount_ro>.  Note that squashfs images are
sometimes non-portable between kernel versions, and they don't support
labels or UUIDs.  If you want to pre-build an image or you need to mount it
using a label or UUID, use an ISO image instead.

=head2 コピー方法

ファイルとデバイスの間でコピーして、仮想マシンのファイルシステムと入出力するための、さまざまなコマンドがあります。以下の表はその概要です。

=over 4

=item B<ファイル>からB<ファイル>

単一のファイルをコピーするには L</guestfs_cp> を使用します、またはディレクトリーを再帰的にコピーするには
L</guestfs_cp_a> を使用します。

To copy part of a file (offset and size) use L</guestfs_copy_file_to_file>.

=item B<ファイル>からB<デバイス>

=item B<デバイス>からB<ファイル>

=item B<デバイス>からB<デバイス>

L</guestfs_copy_file_to_device>, L</guestfs_copy_device_to_file>, または
L</guestfs_copy_device_to_device> を使用してください。

例: 論理ボリュームの内容の複製:

 guestfs_copy_device_to_device (g,
         "/dev/VG/Original", "/dev/VG/Copy",
         /* -1 marks the end of the list of optional parameters */
         -1);

The destination (C</dev/VG/Copy>) must be at least as large as the source
(C</dev/VG/Original>).  To copy less than the whole source device, use the
optional C<size> parameter:

 guestfs_copy_device_to_device (g,
         "/dev/VG/Original", "/dev/VG/Copy",
         GUESTFS_COPY_DEVICE_TO_DEVICE_SIZE, 10000,
         -1);

=item B<ホストのファイル>からB<ファイルまたはデバイス>

L</guestfs_upload> を使用します。上の L</アップロード方法> 参照。

=item B<ファイルまたはデバイス>からB<ホストのファイル>

L</guestfs_download> を使用します。上の L</ダウンロード方法> 参照。

=back

=head2 UPLOADING AND DOWNLOADING TO PIPES AND FILE DESCRIPTORS

Calls like L</guestfs_upload>, L</guestfs_download>, L</guestfs_tar_in>,
L</guestfs_tar_out> etc appear to only take filenames as arguments, so it
appears you can only upload and download to files.  However many Un*x-like
hosts let you use the special device files C</dev/stdin>, C</dev/stdout>,
C</dev/stderr> and C</dev/fd/N> to read and write from stdin, stdout,
stderr, and arbitrary file descriptor N.

たとえば、L<virt-cat(1)> は次のようにすることにより、出力を標準出力に書き込みます:

 guestfs_download (g, filename, "/dev/stdout");

and you can write tar output to a file descriptor C<fd> by doing:

 char devfd[64];
 snprintf (devfd, sizeof devfd, "/dev/fd/%d", fd);
 guestfs_tar_out (g, "/", devfd);

=head2 ファイルの一覧表示方法

L</guestfs_ll> は人間が読みやすいよう設計されています（おもに L<guestfish(1)> の同等なコマンド C<ll>
を使用するとき）。

L</guestfs_ls> は文字列の平らな一覧のように、ディレクトリーにあるファイルの一覧をプログラムから取得する素早い方法です。

L</guestfs_readdir>
はディレクトリーにあるファイルの一覧、さらにそれぞれに関する追加の情報を取得するためのプログラム的な方法です。ローカルシステムにおける
L<readdir(3)> 呼び出しを使用することとほぼ同様です。

L</guestfs_find> と L</guestfs_find0> は再帰的にファイルを一覧表示するために使用できます。

=head2 コマンドの実行法

libguestfs はおもに仮想マシンの中にあるファイルを操作するための API
です。さらに、仮想マシンの中にあるコマンドを実行するために、限定された機能がいくつかあります。

これには多くの制限があります:

=over 4

=item *

コマンドを実行するカーネルのバージョンは、期待するものにより異なります。

=item *

コマンドがデーモンと通信する必要があれば、ほとんど動作しないでしょう。

=item *

コマンドは制限されたメモリーにおいて実行されます。

=item *

ネットワークは有効にしなければ利用できません（L</guestfs_set_network> 参照）。

=item *

Linux ゲストのみがサポートされます（Windows, BSD など）。

=item *

アーキテクチャーの制限（例: x86 ホストにおいて PPC ゲストは動作しません）。

=item *

SELinux 仮想マシンに対しては、まず SELinux を有効にして、ポリシーを読み込む必要があります。このマニュアルページにおいて
L</SELinux> を参照してください。

=item *

I<Security:> It is not safe to run commands from untrusted, possibly
malicious guests.  These commands may attempt to exploit your program by
sending unexpected output.  They could also try to exploit the Linux kernel
or qemu provided by the libguestfs appliance.  They could use the network
provided by the libguestfs appliance to bypass ordinary network partitions
and firewalls.  They could use the elevated privileges or different SELinux
context of your program to their advantage.

A secure alternative is to use libguestfs to install a "firstboot" script (a
script which runs when the guest next boots normally), and to have this
script run the commands you want in the normal context of the running guest,
network security and so on.  For information about other security issues,
see L</SECURITY>.

=back

The two main API calls to run commands are L</guestfs_command> and
L</guestfs_sh> (there are also variations).

The difference is that L</guestfs_sh> runs commands using the shell, so any
shell globs, redirections, etc will work.

=head2 設定ファイル

To read and write configuration files in Linux guest filesystems, we
strongly recommend using Augeas.  For example, Augeas understands how to
read and write, say, a Linux shadow password file or X.org configuration
file, and so avoids you having to write that code.

The main Augeas calls are bound through the C<guestfs_aug_*> APIs.  We don't
document Augeas itself here because there is excellent documentation on the
L<http://augeas.net/> website.

If you don't want to use Augeas (you fool!) then try calling
L</guestfs_read_lines> to get the file as a list of lines which you can
iterate over.

=head2 SELinux

SELinux ゲストをサポートします。  SELinux ゲストにおいて正しくラベルづけされていることを確認するには、SELinux
を有効にして、ゲストのポリシーを読み込む必要があります:

=over 4

=item 1.

起動前に次を実行します:

 guestfs_set_selinux (g, 1);

=item 2.

ゲストのファイルシステムをマウント後、ポリシーを読み込みます。  これはゲスト自身において L<load_policy(8)>
コマンドを実行することが一番です:

 guestfs_sh (g, "/usr/sbin/load_policy");

（古いバージョンの C<load_policy> はポリシーファイルの名前を指定する必要があります）。

=item 3.

オプションとして、API のセキュリティコンテキストを設定します。
使用する適切なセキュリティコンテキストは、ゲストを検査することによってのみ知ることができます。  以下の例のようです:

 guestfs_setcon (g, "unconfined_u:unconfined_r:unconfined_t:s0");

=back

コマンドを実行し、既存のファイルを編集するために機能します。

When new files are created, you may need to label them explicitly, for
example by running the external command C<restorecon pathname>.

=head2 umask

Certain calls are affected by the current file mode creation mask (the
"umask").  In particular ones which create files or directories, such as
L</guestfs_touch>, L</guestfs_mknod> or L</guestfs_mkdir>.  This affects
either the default mode that the file is created with or modifies the mode
that you supply.

umask の初期値は C<022> です、そのためファイルは C<0644> のようなモードで作成され、ディレクトリーは C<0755> です。

umask による影響を避けるには 2 つの方法があります。1 つは umask を 0 に設定することです（開始後の早いうちに
C<guestfs_umask (g, 0)> を呼び出します）。もう 1 つは各ファイルまたはディレクトリーを作成した後に
L</guestfs_chmod> を呼び出すことです。

umask に関する詳細は L<umask(2)> を参照してください。

=head2 暗号化ディスク

Libguestfs allows you to access Linux guests which have been encrypted using
whole disk encryption that conforms to the Linux Unified Key Setup (LUKS)
standard.  This includes nearly all whole disk encryption systems used by
modern Linux guests.

LUKS 暗号化ブロックデバイス（それは文字列 C<crypto_LUKS> を返します）を識別するには L</guestfs_vfs_type>
を使用します。

そして L</guestfs_luks_open> を呼び出すことにより、これらのデバイスを開きます。明示的にパスフレーズが必要です。

Opening a LUKS device creates a new device mapper device called
C</dev/mapper/mapname> (where C<mapname> is the string you supply to
L</guestfs_luks_open>).  Reads and writes to this mapper device are
decrypted from and encrypted to the underlying block device respectively.

LVM volume groups on the device can be made visible by calling
L</guestfs_vgscan> followed by L</guestfs_vg_activate_all>.  The logical
volume(s) can now be mounted in the usual way.

Use the reverse process to close a LUKS device.  Unmount any logical volumes
on it, deactivate the volume groups by caling C<guestfs_vg_activate (g, 0,
["/dev/VG"])>.  Then close the mapper device by calling
L</guestfs_luks_close> on the C</dev/mapper/mapname> device (I<not> the
underlying encrypted block device).

=head2 MOUNT LOCAL

In libguestfs E<ge> 1.18, it is possible to mount the libguestfs filesystem
on a local directory and access it using ordinary POSIX calls and programs.

Availability of this is subject to a number of restrictions: it requires
FUSE (the Filesystem in USErspace), and libfuse must also have been
available when libguestfs was compiled.  FUSE may require that a kernel
module is loaded, and it may be necessary to add the current user to a
special C<fuse> group.  See the documentation for your distribution and
L<http://fuse.sf.net> for further information.

The call to mount the libguestfs filesystem on a local directory is
L</guestfs_mount_local> (q.v.) followed by L</guestfs_mount_local_run>.  The
latter does not return until you unmount the filesystem.  The reason is that
the call enters the FUSE main loop and processes kernel requests, turning
them into libguestfs calls.  An alternative design would have been to create
a background thread to do this, but libguestfs doesn't require pthreads.
This way is also more flexible: for example the user can create another
thread for L</guestfs_mount_local_run>.

L</guestfs_mount_local> needs a certain amount of time to set up the
mountpoint.  The mountpoint is not ready to use until the call returns.  At
this point, accesses to the filesystem will block until the main loop is
entered (ie. L</guestfs_mount_local_run>).  So if you need to start another
process to access the filesystem, put the fork between
L</guestfs_mount_local> and L</guestfs_mount_local_run>.

=head3 MOUNT LOCAL COMPATIBILITY

Since local mounting was only added in libguestfs 1.18, and may not be
available even in these builds, you should consider writing code so that it
doesn't depend on this feature, and can fall back to using libguestfs file
system calls.

If libguestfs was compiled without support for L</guestfs_mount_local> then
calling it will return an error with errno set to C<ENOTSUP> (see
L</guestfs_last_errno>).

=head3 MOUNT LOCAL PERFORMANCE

Libguestfs on top of FUSE performs quite poorly.  For best performance do
not use it.  Use ordinary libguestfs filesystem calls, upload, download
etc. instead.

=head2 INSPECTION

Libguestfs has APIs for inspecting an unknown disk image to find out if it
contains operating systems, an install CD or a live CD.  (These APIs used to
be in a separate Perl-only library called L<Sys::Guestfs::Lib(3)> but since
version 1.5.3 the most frequently used part of this library has been
rewritten in C and moved into the core code).

Add all disks belonging to the unknown virtual machine and call
L</guestfs_launch> in the usual way.

Then call L</guestfs_inspect_os>.  This function uses other libguestfs calls
and certain heuristics, and returns a list of operating systems that were
found.  An empty list means none were found.  A single element is the root
filesystem of the operating system.  For dual- or multi-boot guests,
multiple roots can be returned, each one corresponding to a separate
operating system.  (Multi-boot virtual machines are extremely rare in the
world of virtualization, but since this scenario can happen, we have built
libguestfs to deal with it.)

For each root, you can then call various C<guestfs_inspect_get_*> functions
to get additional details about that operating system.  For example, call
L</guestfs_inspect_get_type> to return the string C<windows> or C<linux> for
Windows and Linux-based operating systems respectively.

Un*x-like and Linux-based operating systems usually consist of several
filesystems which are mounted at boot time (for example, a separate boot
partition mounted on C</boot>).  The inspection rules are able to detect how
filesystems correspond to mount points.  Call
C<guestfs_inspect_get_mountpoints> to get this mapping.  It might return a
hash table like this example:

 /boot => /dev/sda1
 /     => /dev/vg_guest/lv_root
 /usr  => /dev/vg_guest/lv_usr

The caller can then make calls to L</guestfs_mount_options> to mount the
filesystems as suggested.

Be careful to mount filesystems in the right order (eg. C</> before
C</usr>).  Sorting the keys of the hash by length, shortest first, should
work.

Inspection currently only works for some common operating systems.
Contributors are welcome to send patches for other operating systems that we
currently cannot detect.

Encrypted disks must be opened before inspection.  See L</ENCRYPTED DISKS>
for more details.  The L</guestfs_inspect_os> function just ignores any
encrypted devices.

I<この関数は推奨されません。> 新しいコードでは、代わりに L</add_drive_opts> を使用してください。

=head3 インストールディスクの検査方法

libguestfs (1.9.4以降) は、いくつかのインストールディスク、インストール CD、live CD などを検知できます。

Call L</guestfs_inspect_get_format> to return the format of the operating
system, which currently can be C<installed> (a regular operating system) or
C<installer> (some sort of install disk).

Further information is available about the operating system that can be
installed using the regular inspection APIs like
L</guestfs_inspect_get_product_name>, L</guestfs_inspect_get_major_version>
etc.

インストールディスクに指定するいくつかの追加情報は L</guestfs_inspect_is_live>,
L</guestfs_inspect_is_netinst> および L</guestfs_inspect_is_multipart>
呼び出しからも取得可能です。

=head2 SPECIAL CONSIDERATIONS FOR WINDOWS GUESTS

libguestfs は NTFS パーティションをマウントできます。そのためには L<http://www.ntfs-3g.org/>
ドライバーを使用します。

=head3 ドライブレターとパス

DOS and Windows still use drive letters, and the filesystems are always
treated as case insensitive by Windows itself, and therefore you might find
a Windows configuration file referring to a path like
C<c:\windows\system32>.  When the filesystem is mounted in libguestfs, that
directory might be referred to as C</WINDOWS/System32>.

Drive letter mappings can be found using inspection (see L</INSPECTION> and
L</guestfs_inspect_get_drive_mappings>)

Dealing with separator characters (backslash vs forward slash) is outside
the scope of libguestfs, but usually a simple character replacement will
work.

To resolve the case insensitivity of paths, call
L</guestfs_case_sensitive_path>.

=head3 Windows レジストリのアクセス方法

I<この関数は推奨されません。> 新しいコードでは、代わりに L</mkfs_opts> を使用してください。

=head3 NTFS-3G ファイルシステムにおけるシンボリックリンク

Ntfs-3g tries to rewrite "Junction Points" and NTFS "symbolic links" to
provide something which looks like a Linux symlink.  The way it tries to do
the rewriting is described here:

L<http://www.tuxera.com/community/ntfs-3g-advanced/junction-points-and-symbolic-links/>

The essential problem is that ntfs-3g simply does not have enough
information to do a correct job.  NTFS links can contain drive letters and
references to external device GUIDs that ntfs-3g has no way of resolving.
It is almost certainly the case that libguestfs callers should ignore what
ntfs-3g does (ie. don't use L</guestfs_readlink> on NTFS volumes).

Instead if you encounter a symbolic link on an ntfs-3g filesystem, use
L</guestfs_lgetxattr> to read the C<system.ntfs_reparse_data> extended
attribute, and read the raw reparse data from that (you can find the format
documented in various places around the web).

=head3 EXTENDED ATTRIBUTES ON NTFS-3G FILESYSTEMS

There are other useful extended attributes that can be read from ntfs-3g
filesystems (using L</guestfs_getxattr>).  See:

L<http://www.tuxera.com/community/ntfs-3g-advanced/extended-attributes/>

=head2 RESIZE2FS ERRORS

The L</guestfs_resize2fs>, L</guestfs_resize2fs_size> and
L</guestfs_resize2fs_M> calls are used to resize ext2/3/4 filesystems.

The underlying program (L<resize2fs(8)>) requires that the filesystem is
clean and recently fsck'd before you can resize it.  Also, if the resize
operation fails for some reason, then you had to call fsck the filesystem
again to fix it.

In libguestfs C<lt> 1.17.14, you usually had to call L</guestfs_e2fsck_f>
before the resize.  However, in C<ge> 1.17.14, L<e2fsck(8)> is called
automatically before the resize, so you no longer need to do this.

The L<resize2fs(8)> program can still fail, in which case it prints an error
message similar to:

 容量変更の操作を中断した後、ファイルシステムを
 修復するために 'e2fsck -fy <device>' を実行してください。

You can do this by calling L</guestfs_e2fsck> with the C<forceall> option.
However in the context of disk images, it is usually better to avoid this
situation, eg. by rolling back to an earlier snapshot, or by copying and
resizing and on failure going back to the original.

=head2 USING LIBGUESTFS WITH OTHER PROGRAMMING LANGUAGES

Although we don't want to discourage you from using the C API, we will
mention here that the same API is also available in other languages.

The API is broadly identical in all supported languages.  This means that
the C call C<guestfs_add_drive_ro(g,file)> is C<$g-E<gt>add_drive_ro($file)>
in Perl, C<g.add_drive_ro(file)> in Python, and C<g#add_drive_ro file> in
OCaml.  In other words, a straightforward, predictable isomorphism between
each language.

Error messages are automatically transformed into exceptions if the language
supports it.

We don't try to "object orientify" parts of the API in OO languages,
although contributors are welcome to write higher level APIs above what we
provide in their favourite languages if they wish.

=over 4

=item B<C++>

C++ プログラムから I<guestfs.h> ヘッダーファイルを使用できます。 C++ API は C API と同一です。 C++
のクラスと例外は使用されません。

=item B<C#>

C# バインディングは非常に実験的です。 C<csharp/Libguestfs.cs> の一番最初にある警告を参照してください。

=item B<Erlang>

L<guestfs-erlang(3)> 参照。

=item B<GObject>

Experimental GObject bindings (with GObject Introspection support) are
available.  See the C<gobject> directory in the source.

=item B<Haskell>

This is the only language binding that is working but incomplete.  Only
calls which return simple integers have been bound in Haskell, and we are
looking for help to complete this binding.

=item B<Java>

Full documentation is contained in the Javadoc which is distributed with
libguestfs.  For examples, see L<guestfs-java(3)>.

=item B<OCaml>

L<guestfs-ocaml(3)> 参照。

=item B<Perl>

L<guestfs-perl(3)> および L<Sys::Guestfs(3)> 参照。

=item B<PHP>

For documentation see C<README-PHP> supplied with libguestfs sources or in
the php-libguestfs package for your distribution.

PHP バインドは 64 ビットマシンにおいてのみ正しく動作します。

=item B<Python>

L<guestfs-python(3)> 参照。

=item B<Ruby>

L<guestfs-ruby(3)> 参照。

JRuby に対しては Java バインドを使用します。

=item B<シェルスクリプト>

L<guestfish(1)> 参照。

=back

=head2 LIBGUESTFS GOTCHAS

L<http://en.wikipedia.org/wiki/Gotcha_(programming)>: "A feature of a system
[...] that works in the way it is documented but is counterintuitive and
almost invites mistakes."

Since we developed libguestfs and the associated tools, there are several
things we would have designed differently, but are now stuck with for
backwards compatibility or other reasons.  If there is ever a libguestfs 2.0
release, you can expect these to change.  Beware of them.

=over 4

=item Autosync / forgetting to sync.

I<Update:> Autosync is enabled by default for all API users starting from
libguestfs 1.5.24.  This section only applies to older versions.

When modifying a filesystem from C or another language, you B<must> unmount
all filesystems and call L</guestfs_sync> explicitly before you close the
libguestfs handle.  You can also call:

 guestfs_set_autosync (g, 1);

to have the unmount/sync done automatically for you when the handle 'g' is
closed.  (This feature is called "autosync", L</guestfs_set_autosync> q.v.)

If you forget to do this, then it is entirely possible that your changes
won't be written out, or will be partially written, or (very rarely) that
you'll get disk corruption.

Note that in L<guestfish(3)> autosync is the default.  So quick and dirty
guestfish scripts that forget to sync will work just fine, which can make
this very puzzling if you are trying to debug a problem.

=item マウントオプション C<-o sync> をデフォルトにすべきではありません。

I<Update:> L</guestfs_mount> no longer adds any options starting from
libguestfs 1.13.16.  This section only applies to older versions.

If you use L</guestfs_mount>, then C<-o sync,noatime> are added implicitly.
However C<-o sync> does not add any reliability benefit, but does have a
very large performance impact.

The work around is to use L</guestfs_mount_options> and set the mount
options that you actually want to use.

=item 初期値は読み込み専用です。

L<guestfish(3)> では、 I<--ro> が初期値です。イメージを変更したいならば I<--rw> を指定する必要があります。

これにより、動作中の仮想マシンのイメージを破壊する可能性を減らします。

Note that many filesystems change the disk when you just mount and unmount,
even if you didn't perform any writes.  You need to use
L</guestfs_add_drive_ro> to guarantee that the disk is not changed.

=item guestfish コマンドラインは使うのが難しいです。

C<guestfish disk.img> doesn't do what people expect (open C<disk.img> for
examination).  It tries to run a guestfish command C<disk.img> which doesn't
exist, so it fails.  In earlier versions of guestfish the error message was
also unintuitive, but we have corrected this since.  Like the Bourne shell,
we should have used C<guestfish -c command> to run commands.

=item guestfish megabyte modifiers don't work right on all commands

In recent guestfish you can use C<1M> to mean 1 megabyte (and similarly for
other modifiers).  What guestfish actually does is to multiply the number
part by the modifier part and pass the result to the C API.  However this
doesn't work for a few APIs which aren't expecting bytes, but are already
expecting some other unit (eg. megabytes).

最も一般的な L</guestfs_lvcreate> です。 guestfish コマンド:

 lvcreate LV VG 100M

does not do what you might expect.  Instead because L</guestfs_lvcreate> is
already expecting megabytes, this tries to create a 100 I<terabyte> (100
megabytes * megabytes) logical volume.  The error message you get from this
is also a little obscure.

This could be fixed in the generator by specially marking parameters and
return values which take bytes or other units.

=item Ambiguity between devices and paths

There is a subtle ambiguity in the API between a device name
(eg. C</dev/sdb2>) and a similar pathname.  A file might just happen to be
called C<sdb2> in the directory C</dev> (consider some non-Unix VM image).

In the current API we usually resolve this ambiguity by having two separate
calls, for example L</guestfs_checksum> and L</guestfs_checksum_device>.
Some API calls are ambiguous and (incorrectly) resolve the problem by
detecting if the path supplied begins with C</dev/>.

To avoid both the ambiguity and the need to duplicate some calls, we could
make paths/devices into structured names.  One way to do this would be to
use a notation like grub (C<hd(0,0)>), although nobody really likes this
aspect of grub.  Another way would be to use a structured type, equivalent
to this OCaml type:

 type path = Path of string | Device of int | Partition of int * int

which would allow you to pass arguments like:

 Path "/foo/bar"
 Device 1            (* /dev/sdb, または場合によると /dev/sda *)
 Partition (1, 2)    (* /dev/sdb2 (または /dev/sda2 や /dev/sdb3?) *)
 Path "/dev/sdb2"    (* デバイスではありません *)

As you can see there are still problems to resolve even with this
representation.  Also consider how it might work in guestfish.

=back

=head2 キーとパスフレーズ

特定の libguestfs 呼び出しは、C 文字列のように渡される、秘密を扱うキーの材料を含むパラメーターをとります。

In the future we would hope to change the libguestfs implementation so that
keys are L<mlock(2)>-ed into physical RAM, and thus can never end up in
swap.  However this is I<not> done at the moment, because of the complexity
of such an implementation.

Therefore you should be aware that any key parameter you pass to libguestfs
might end up being written out to the swap partition.  If this is a concern,
scrub the swap partition or don't use libguestfs on encrypted devices.

=head2 MULTIPLE HANDLES AND MULTIPLE THREADS

All high-level libguestfs actions are synchronous.  If you want to use
libguestfs asynchronously then you must create a thread.

Only use the handle from a single thread.  Either use the handle exclusively
from one thread, or provide your own mutex so that two threads cannot issue
calls on the same handle at the same time.

See the graphical program guestfs-browser for one possible architecture for
multithreaded programs using libvirt and libguestfs.

=head2 パス

Libguestfs needs a supermin appliance, which it finds by looking along an
internal path.

デフォルトで、ディレクトリー C<$libdir/guestfs> にあるこれらに対して見えます (例:
C</usr/local/lib/guestfs> または C</usr/lib64/guestfs>)。

Use L</guestfs_set_path> or set the environment variable L</LIBGUESTFS_PATH>
to change the directories that libguestfs will search in.  The value is a
colon-separated list of paths.  The current directory is I<not> searched
unless the path contains an empty element or C<.>.  For example
C<LIBGUESTFS_PATH=:/usr/lib/guestfs> would search the current directory and
then C</usr/lib/guestfs>.

=head2 QEMU ラッパー

自身の QEMU をコンパイルしたい、非標準の場所から QEMU を実行したい、または追加の引数を QEMU に渡したいならば、QEMU
のシェルスクリプト・ラッパーを書けます。

There is one important rule to remember: you I<must C<exec qemu>> as the
last command in the shell script (so that qemu replaces the shell and
becomes the direct child of the libguestfs-using program).  If you don't do
this, then the qemu process won't be cleaned up correctly.

Here is an example of a wrapper, where I have built my own copy of qemu from
source:

 #!/bin/sh -
 qemudir=/home/rjones/d/qemu
 exec $qemudir/x86_64-softmmu/qemu-system-x86_64 -L $qemudir/pc-bios "$@"

Save this script as C</tmp/qemu.wrapper> (or wherever), C<chmod +x>, and
then use it by setting the LIBGUESTFS_QEMU environment variable.  For
example:

 LIBGUESTFS_QEMU=/tmp/qemu.wrapper guestfish

Note that libguestfs also calls qemu with the -help and -version options in
order to determine features.

Wrappers can also be used to edit the options passed to qemu.  In the
following example, the C<-machine ...> option (C<-machine> and the following
argument) are removed from the command line and replaced with C<-machine
pc,accel=tcg>.  The while loop iterates over the options until it finds the
right one to remove, putting the remaining options into the C<args> array.

 #!/bin/bash -
 
 i=0
 while [ $# -gt 0 ]; do
     case "$1" in
     -machine)
         shift 2;;
     *)
         args[i]="$1"
         (( i++ ))
         shift ;;
     esac
 done
 
 exec qemu-kvm -machine pc,accel=tcg "${args[@]}"

=head2 ATTACHING TO RUNNING DAEMONS

I<Note (1):> This is B<highly experimental> and has a tendency to eat
babies.  Use with caution.

I<Note (2):> This section explains how to attach to a running daemon from a
low level perspective.  For most users, simply using virt tools such as
L<guestfish(1)> with the I<--live> option will "just work".

=head3 guestfs_set_attach_method の使用法

By calling L</guestfs_set_attach_method> you can change how the library
connects to the C<guestfsd> daemon in L</guestfs_launch> (read
L</ARCHITECTURE> for some background).

The normal attach method is C<appliance>, where a small appliance is created
containing the daemon, and then the library connects to this.

Setting attach method to C<unix:I<path>> (where I<path> is the path of a
Unix domain socket) causes L</guestfs_launch> to connect to an existing
daemon over the Unix domain socket.

The normal use for this is to connect to a running virtual machine that
contains a C<guestfsd> daemon, and send commands so you can read and write
files inside the live virtual machine.

=head3 live フラグを用いた guestfs_add_domain の使用方法

I<この関数は推奨されません。> 新しいコードでは、代わりに L</ntfsresize_opts> を使用してください。

 <domain>
   ...
   <devices>
     ...
     <channel type='unix'>
       <source mode='bind' path='/path/to/socket'/>
       <target type='virtio' name='org.libguestfs.channel.0'/>
     </channel>
     ...
   </devices>
 </domain>

L</guestfs_add_domain> は C</path/to/socket> を抽出し、接続方法を
C<unix:/path/to/socket> に設定します。

Some of the libguestfs tools (including guestfish) support a I<--live>
option which is passed through to L</guestfs_add_domain> thus allowing you
to attach to and modify live virtual machines.

The virtual machine needs to have been set up beforehand so that it has the
virtio-serial channel and so that guestfsd is running inside it.

=head2 ABI 保証

We guarantee the libguestfs ABI (binary interface), for public, high-level
actions as outlined in this section.  Although we will deprecate some
actions, for example if they get replaced by newer calls, we will keep the
old actions forever.  This allows you the developer to program in confidence
against the libguestfs API.

=head2 ブロックデバイスの命名法

In the kernel there is now quite a profusion of schemata for naming block
devices (in this context, by I<block device> I mean a physical or virtual
hard drive).  The original Linux IDE driver used names starting with
C</dev/hd*>.  SCSI devices have historically used a different naming scheme,
C</dev/sd*>.  When the Linux kernel I<libata> driver became a popular
replacement for the old IDE driver (particularly for SATA devices) those
devices also used the C</dev/sd*> scheme.  Additionally we now have virtual
machines with paravirtualized drivers.  This has created several different
naming systems, such as C</dev/vd*> for virtio disks and C</dev/xvd*> for
Xen PV disks.

As discussed above, libguestfs uses a qemu appliance running an embedded
Linux kernel to access block devices.  We can run a variety of appliances
based on a variety of Linux kernels.

This causes a problem for libguestfs because many API calls use device or
partition names.  Working scripts and the recipe (example) scripts that we
make available over the internet could fail if the naming scheme changes.

Therefore libguestfs defines C</dev/sd*> as the I<standard naming scheme>.
Internally C</dev/sd*> names are translated, if necessary, to other names as
required.  For example, under RHEL 5 which uses the C</dev/hd*> scheme, any
device parameter C</dev/sda2> is translated to C</dev/hda2> transparently.

Note that this I<only> applies to parameters.  The L</guestfs_list_devices>,
L</guestfs_list_partitions> and similar calls return the true names of the
devices and partitions as known to the appliance.

=head3 ALGORITHM FOR BLOCK DEVICE NAME TRANSLATION

Usually this translation is transparent.  However in some (very rare)  cases
you may need to know the exact algorithm.  Such cases include where you use
L</guestfs_config> to add a mixture of virtio and IDE devices to the
qemu-based appliance, so have a mixture of C</dev/sd*> and C</dev/vd*>
devices.

The algorithm is applied only to I<parameters> which are known to be either
device or partition names.  Return values from functions such as
L</guestfs_list_devices> are never changed.

=over 4

=item *

Is the string a parameter which is a device or partition name?

=item *

文字列が C</dev/sd> で始まっていますか？

=item *

名前付きのデバイスが存在しますか？そうならば、そのデバイスを使用します。しかし、そうで I<なければ> 、この手順を続けます。

=item *

最初の C</dev/sd> 文字列を C</dev/hd> で置き換えます。

たとえば、 C</dev/sda2> を C</dev/hda2> に変更します。

名前付きデバイスが存在すれば、それを使用します。なければ、続けます。

=item *

最初の C</dev/sd> 文字列を C</dev/vd> で置き換えます。

名前付きデバイスが存在すれば、それを使用します。なければ、エラーを返します。

=back

=head3 PORTABILITY CONCERNS WITH BLOCK DEVICE NAMING

Although the standard naming scheme and automatic translation is useful for
simple programs and guestfish scripts, for larger programs it is best not to
rely on this mechanism.

Where possible for maximum future portability programs using libguestfs
should use these future-proof techniques:

=over 4

=item *

実際のデバイス名を一覧表示するには L</guestfs_list_devices> または L</guestfs_list_partitions>
を使用します。そして、それらの名前を直接使用します。

それらのデバイス名が定義により存在しているので、それらは変換されません。

=item *

LVM 名、UUID およびファイルシステムのラベルのように、ファイルシステムを識別するための高レベルの方法を使用します。

=back

=head1 セキュリティ

このセクションは libguestfs
を使用するときのセキュリティ実装、とくに信頼されない、または悪意のある仮想マシンやディスクイメージを用いる場合について議論します。

=head2 一般的なセキュリティ考慮事項

Be careful with any files or data that you download from a guest (by
"download" we mean not just the L</guestfs_download> command but any command
that reads files, filenames, directories or anything else from a disk
image).  An attacker could manipulate the data to fool your program into
doing the wrong thing.  Consider cases such as:

=over 4

=item *

データ（ファイルなど）が存在しない場合

=item *

存在するが空の場合

=item *

通常よりもかなり大きい場合

=item *

任意の 8 ビットのデータを含む場合

=item *

予期しない文字エンコードを使用している場合

=item *

同型異義語を含む場合

=back

=head2 SECURITY OF MOUNTING FILESYSTEMS

When you mount a filesystem under Linux, mistakes in the kernel filesystem
(VFS) module can sometimes be escalated into exploits by deliberately
creating a malicious, malformed filesystem.  These exploits are very severe
for two reasons.  Firstly there are very many filesystem drivers in the
kernel, and many of them are infrequently used and not much developer
attention has been paid to the code.  Linux userspace helps potential
crackers by detecting the filesystem type and automatically choosing the
right VFS driver, even if that filesystem type is obscure or unexpected for
the administrator.  Secondly, a kernel-level exploit is like a local root
exploit (worse in some ways), giving immediate and total access to the
system right down to the hardware level.

That explains why you should never mount a filesystem from an untrusted
guest on your host kernel.  How about libguestfs? We run a Linux kernel
inside a qemu virtual machine, usually running as a non-root user.  The
attacker would need to write a filesystem which first exploited the kernel,
and then exploited either qemu virtualization (eg. a faulty qemu driver) or
the libguestfs protocol, and finally to be as serious as the host kernel
exploit it would need to escalate its privileges to root.  This multi-step
escalation, performed by a static piece of data, is thought to be extremely
hard to do, although we never say 'never' about security issues.

In any case callers can reduce the attack surface by forcing the filesystem
type when mounting (use L</guestfs_mount_vfs>).

=head2 プロトコルセキュリティ

プロトコルは、定義されたメッセージ上限容量を持つ RFC 4506 (XDR)
に基づき、セキュアであるように設計されています。しかしながら、libguestfs を使用するプログラムは気をつけなければいけません -
たとえば、ディスクイメージからバイナリーをダウンロードして、ローカルに実行するプログラムを書くことができます。また、多くのプロトコルセキュリティは結果からあなたを保護しません。

=head2 INSPECTION SECURITY

Parts of the inspection API (see L</INSPECTION>) return untrusted strings
directly from the guest, and these could contain any 8 bit data.  Callers
should be careful to escape these before printing them to a structured file
(for example, use HTML escaping if creating a web page).

Guest configuration may be altered in unusual ways by the administrator of
the virtual machine, and may not reflect reality (particularly for untrusted
or actively malicious guests).  For example we parse the hostname from
configuration files like C</etc/sysconfig/network> that we find in the
guest, but the guest administrator can easily manipulate these files to
provide the wrong hostname.

The inspection API parses guest configuration using two external libraries:
Augeas (Linux configuration) and hivex (Windows Registry).  Both are
designed to be robust in the face of malicious data, although denial of
service attacks are still possible, for example with oversized configuration
files.

=head2 RUNNING UNTRUSTED GUEST COMMANDS

Be very cautious about running commands from the guest.  By running a
command in the guest, you are giving CPU time to a binary that you do not
control, under the same user account as the library, albeit wrapped in qemu
virtualization.  More information and alternatives can be found in the
section L</RUNNING COMMANDS>.

=head2 CVE-2010-3851

https://bugzilla.redhat.com/642934

このセキュリティバグは、QEMU のディスクイメージでないことをディスクの自動フォーマット検出に関するものです。

A raw disk image is just the raw bytes, there is no header.  Other disk
images like qcow2 contain a special header.  Qemu deals with this by looking
for one of the known headers, and if none is found then assuming the disk
image must be raw.

This allows a guest which has been given a raw disk image to write some
other header.  At next boot (or when the disk image is accessed by
libguestfs) qemu would do autodetection and think the disk image format was,
say, qcow2 based on the header written by the guest.

This in itself would not be a problem, but qcow2 offers many features, one
of which is to allow a disk image to refer to another image (called the
"backing disk").  It does this by placing the path to the backing disk into
the qcow2 header.  This path is not validated and could point to any host
file (eg. "/etc/passwd").  The backing disk is then exposed through "holes"
in the qcow2 disk image, which of course is completely under the control of
the attacker.

In libguestfs this is rather hard to exploit except under two circumstances:

=over 4

=item 1.

ネットワークを有効化しているか、もしくは書き込みモードでディスクを開いています。

=item 2.

You are also running untrusted code from the guest (see L</RUNNING
COMMANDS>).

=back

The way to avoid this is to specify the expected disk format when adding
disks (the optional C<format> option to L</guestfs_add_drive_opts>).  You
should always do this if the disk is raw format, and it's a good idea for
other cases too.

For disks added from libvirt using calls like L</guestfs_add_domain>, the
format is fetched from libvirt and passed through.

For libguestfs tools, use the I<--format> command line parameter as
appropriate.

=head1 CONNECTION MANAGEMENT

=head2 guestfs_h *

C<guestfs_h> is the opaque type representing a connection handle.  Create a
handle by calling L</guestfs_create>.  Call L</guestfs_close> to free the
handle and release all resources used.

For information on using multiple handles and threads, see the section
L</MULTIPLE HANDLES AND MULTIPLE THREADS> above.

=head2 guestfs_create

 guestfs_h *guestfs_create (void);

接続ハンドルを作成します。

On success this returns a non-NULL pointer to a handle.  On error it returns
NULL.

You have to "configure" the handle after creating it.  This includes calling
L</guestfs_add_drive_opts> (or one of the equivalent calls) on the handle at
least once.

ハンドルを設定後、 L</guestfs_launch> を呼び出す必要があります。

You may also want to configure error handling for the handle.  See the
L</ERROR HANDLING> section below.

=head2 guestfs_close

 void guestfs_close (guestfs_h *g);

これにより、接続ハンドルを閉じ、すべての使用資源を解放します。

If autosync was set on the handle and the handle was launched, then this
implicitly calls various functions to unmount filesystems and sync the
disk.  See L</guestfs_set_autosync> for more details.

If a close callback was set on the handle, then it is called.

=head1 エラー処理

API 関数はエラーを返します。たとえば、ほとんどすべての C<int> を返す関数はエラーを意味するために C<-1> を返します。

エラーに関する追加の情報が利用可能です: 失敗したものがシステムコールならば、エラーメッセージ文字列およびオプションのエラー番号（errno）です。

You can get at the additional information about the last error on the handle
by calling L</guestfs_last_error>, L</guestfs_last_errno>, and/or by setting
up an error handler with L</guestfs_set_error_handler>.

When the handle is created, a default error handler is installed which
prints the error message string to C<stderr>.  For small short-running
command line programs it is sufficient to do:

 if (guestfs_launch (g) == -1)
   exit (EXIT_FAILURE);

since the default error handler will ensure that an error message has been
printed to C<stderr> before the program exits.

For other programs the caller will almost certainly want to install an
alternate error handler or do error handling in-line like this:

 /* これは標準エラーにエラーを表示するときの
    デフォルトの動作を無効化します。 */
 guestfs_set_error_handler (g, NULL, NULL);
 
 if (guestfs_launch (g) == -1) {
   /* Examine the error message and print it etc. */
   char *msg = guestfs_last_error (g);
   int errnum = guestfs_last_errno (g);
   fprintf (stderr, "%s", msg);
   if (errnum != 0)
     fprintf (stderr, ": %s", strerror (errnum));
   fprintf (stderr, "\n");
   /* ... */
 }

Out of memory errors are handled differently.  The default action is to call
L<abort(3)>.  If this is undesirable, then you can set a handler using
L</guestfs_set_out_of_memory_handler>.

L</guestfs_create> returns C<NULL> if the handle cannot be created, and
because there is no handle if this happens there is no way to get additional
error information.  However L</guestfs_create> is supposed to be a
lightweight operation which can only fail because of insufficient memory (it
returns NULL in this case).

=head2 guestfs_last_error

 const char *guestfs_last_error (guestfs_h *g);

This returns the last error message that happened on C<g>.  If there has not
been an error since the handle was created, then this returns C<NULL>.

返された文字列の有効期間は、次のエラーが発生するまで、または L</guestfs_close> が呼び出されるまでです。

=head2 guestfs_last_errno

 int guestfs_last_errno (guestfs_h *g);

これは C<g> において発生した最後のエラー番号（errno）を返します。

もし成功すると、0 以外のエラー番号の整数が返されます。

もしエラーがなければ、これは 0 を返します。この呼び出しは 3 つの状況において 0 を返す可能性があります:

=over 4

=item 1.

ハンドルにおいて何もエラーがありませんでした。

=item 2.

エラーがありましたが、エラー番号に意味がありませんでした。エラーがシステムコールの失敗により発生しましたが、何か他の理由による場合に対応します。

=item 3.

エラーがシステムコールの失敗により発生しましたが、エラー番号が何らかの理由により捕捉されず返されました。これは通常 libguestfs
のバグを意味します。

=back

Libguestfs tries to convert the errno from inside the applicance into a
corresponding errno for the caller (not entirely trivial: the appliance
might be running a completely different operating system from the library
and error numbers are not standardized across Un*xen).  If this could not be
done, then the error is translated to C<EINVAL>.  In practice this should
only happen in very rare circumstances.

=head2 guestfs_set_error_handler

 typedef void (*guestfs_error_handler_cb) (guestfs_h *g,
                                           void *opaque,
                                           const char *msg);
 void guestfs_set_error_handler (guestfs_h *g,
                                 guestfs_error_handler_cb cb,
                                 void *opaque);

The callback C<cb> will be called if there is an error.  The parameters
passed to the callback are an opaque data pointer and the error message
string.

C<errno> is not passed to the callback.  To get that the callback must call
L</guestfs_last_errno>.

Note that the message string C<msg> is freed as soon as the callback
function returns, so if you want to stash it somewhere you must make your
own copy.

The default handler prints messages on C<stderr>.

If you set C<cb> to C<NULL> then I<no> handler is called.

=head2 guestfs_get_error_handler

 guestfs_error_handler_cb guestfs_get_error_handler (guestfs_h *g,
                                                     void **opaque_rtn);

現在のエラーハンドラのコールバックを返します。

=head2 guestfs_set_out_of_memory_handler

 typedef void (*guestfs_abort_cb) (void);
 void guestfs_set_out_of_memory_handler (guestfs_h *g,
                                         guestfs_abort_cb);

The callback C<cb> will be called if there is an out of memory situation.
I<Note this callback must not return>.

デフォルトでは L<abort(3)> を呼び出します。

C<cb> を C<NULL> に設定できません。メモリー不足の状況を無視できません。

=head2 guestfs_get_out_of_memory_handler

 guestfs_abort_fn guestfs_get_out_of_memory_handler (guestfs_h *g);

アウトオブメモリーハンドラーを返します。

=head1 API 呼び出し

@ACTIONS@

=head1 構造

@STRUCTS@

=head1 可用性

=head2 アプライアンスの機能のグループ

I<この関数は推奨されません。> 新しいコードでは、代わりに L</part_add> を使用してください。

@AVAILABILITY@

=head2 guestfish がサポートするコマンド

In L<guestfish(3)> there is a handy interactive command C<supported> which
prints out the available groups and whether they are supported by this build
of libguestfs.  Note however that you have to do C<run> first.

=head2 SINGLE CALLS AT COMPILE TIME

バージョン 1.5.8 から C<E<lt>guestfs.hE<gt>> に定義されたシンボルの C API
関数があります。次のようなものがあります:

 #define LIBGUESTFS_HAVE_DD 1

L</guestfs_dd> が利用可能な場合。

Before version 1.5.8, if you needed to test whether a single libguestfs
function is available at compile time, we recommended using build tools such
as autoconf or cmake.  For example in autotools you could use:

 AC_CHECK_LIB([guestfs],[guestfs_create])
 AC_CHECK_FUNCS([guestfs_dd])

which would result in C<HAVE_GUESTFS_DD> being either defined or not defined
in your program.

=head2 SINGLE CALLS AT RUN TIME

I<この関数は推奨されません。> 新しいコードでは、代わりに L</part_list> を使用してください。

I<この関数は推奨されません。> 新しいコードでは、代わりに L</write> を使用してください。

 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <dlfcn.h>
 #include <guestfs.h>
 
 main ()
 {
 #ifdef LIBGUESTFS_HAVE_DD
   void *dl;
   int has_function;
 
   /* guestfs_dd 関数が本当に利用可能かを確認します。 */
   dl = dlopen (NULL, RTLD_LAZY);
   if (!dl) {
     fprintf (stderr, "dlopen: %s\n", dlerror ());
     exit (EXIT_FAILURE);
   }
   has_function = dlsym (dl, "guestfs_dd") != NULL;
   dlclose (dl);
 
   if (!has_function)
     printf ("この libguestfs.so は guestfs_dd 関数がありません\n");
   else {
     printf ("この libguestfs.so は guestfs_dd 関数があります\n");
     /* Now it's safe to call
     guestfs_dd (g, "foo", "bar");
     */
   }
 #else
   printf ("guestfs_dd 関数がコンパイル時に見つかりませんでした\n");
 #endif
  }

You may think the above is an awful lot of hassle, and it is.  There are
other ways outside of the C linking system to ensure that this kind of
incompatibility never arises, such as using package versioning:

 Requires: libguestfs >= 1.0.80

=head1 CALLS WITH OPTIONAL ARGUMENTS

A recent feature of the API is the introduction of calls which take optional
arguments.  In C these are declared 3 ways.  The main way is as a call which
takes variable arguments (ie. C<...>), as in this example:

 int guestfs_add_drive_opts (guestfs_h *g, const char *filename, ...);

Call this with a list of optional arguments, terminated by C<-1>.  So to
call with no optional arguments specified:

 guestfs_add_drive_opts (g, filename, -1);

単一の引数の場合:

 guestfs_add_drive_opts (g, filename,
                         GUESTFS_ADD_DRIVE_OPTS_FORMAT, "qcow2",
                         -1);

2つの引数の場合:

 guestfs_add_drive_opts (g, filename,
                         GUESTFS_ADD_DRIVE_OPTS_FORMAT, "qcow2",
                         GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
                         -1);

and so forth.  Don't forget the terminating C<-1> otherwise Bad Things will
happen!

=head2 USING va_list FOR OPTIONAL ARGUMENTS

I<この関数は推奨されません。> 新しいコードでは、代わりに L</guestfs_add_drive_opts> を使用してください。

 int guestfs_add_drive_opts_va (guestfs_h *g, const char *filename,
                                va_list args);

=head2 CONSTRUCTING OPTIONAL ARGUMENTS

The third variant is useful where you need to construct these calls.  You
pass in a structure where you fill in the optional fields.  The structure
has a bitmask as the first element which you must set to indicate which
fields you have filled in.  For our example function the structure and call
are declared:

 struct guestfs_add_drive_opts_argv {
   uint64_t bitmask;
   int readonly;
   const char *format;
   /* ... */
 };
 int guestfs_add_drive_opts_argv (guestfs_h *g, const char *filename,
              const struct guestfs_add_drive_opts_argv *optargs);

次のように呼び出すことができます。

 struct guestfs_add_drive_opts_argv optargs = {
   .bitmask = GUESTFS_ADD_DRIVE_OPTS_READONLY_BITMASK |
              GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK,
   .readonly = 1,
   .format = "qcow2"
 };
 
 guestfs_add_drive_opts_argv (g, filename, &optargs);

注:

=over 4

=item *

The C<_BITMASK> suffix on each option name when specifying the bitmask.

=item *

You do not need to fill in all fields of the structure.

=item *

There must be a one-to-one correspondence between fields of the structure
that are filled in, and bits set in the bitmask.

=back

=head2 OPTIONAL ARGUMENTS IN OTHER LANGUAGES

In other languages, optional arguments are expressed in the way that is
natural for that language.  We refer you to the language-specific
documentation for more details on that.

guestfish は L<guestfish(1)/OPTIONAL ARGUMENTS> を参照してください。

=head2 SETTING CALLBACKS TO HANDLE EVENTS

B<Note:> This section documents the generic event mechanism introduced in
libguestfs 1.10, which you should use in new code if possible.  The old
functions C<guestfs_set_log_message_callback>,
C<guestfs_set_subprocess_quit_callback>,
C<guestfs_set_launch_done_callback>, C<guestfs_set_close_callback> and
C<guestfs_set_progress_callback> are no longer documented in this manual
page.  Because of the ABI guarantee, the old functions continue to work.

Handles generate events when certain things happen, such as log messages
being generated, progress messages during long-running operations, or the
handle being closed.  The API calls described below let you register a
callback to be called when events happen.  You can register multiple
callbacks (for the same, different or overlapping sets of events), and
individually remove callbacks.  If callbacks are not removed, then they
remain in force until the handle is closed.

In the current implementation, events are only generated synchronously: that
means that events (and hence callbacks) can only happen while you are in the
middle of making another libguestfs call.  The callback is called in the
same thread.

Events may contain a payload, usually nothing (void), an array of 64 bit
unsigned integers, or a message buffer.  Payloads are discussed later on.

=head3 イベントのクラス

=over 4

=item GUESTFS_EVENT_CLOSE (ペイロード形式: void)

The callback function will be called while the handle is being closed
(synchronously from L</guestfs_close>).

I<この関数は推奨されません。> 新しいコードでは、代わりに L</guestfs_fallocate64> を使用してください。

If no callback is registered: the handle is closed without any callback
being invoked.

=item GUESTFS_EVENT_SUBPROCESS_QUIT (ペイロード形式: void)

The callback function will be called when the child process quits, either
asynchronously or if killed by L</guestfs_kill_subprocess>.  (This
corresponds to a transition from any state to the CONFIG state).

If no callback is registered: the event is ignored.

=item GUESTFS_EVENT_LAUNCH_DONE (ペイロード形式: void)

The callback function will be called when the child process becomes ready
first time after it has been launched.  (This corresponds to a transition
from LAUNCHING to the READY state).

If no callback is registered: the event is ignored.

=item GUESTFS_EVENT_PROGRESS (ペイロード形式: 4 x uint64_t の配列)

Some long-running operations can generate progress messages.  If this
callback is registered, then it will be called each time a progress message
is generated (usually two seconds after the operation started, and three
times per second thereafter until it completes, although the frequency may
change in future versions).

The callback receives in the payload four unsigned 64 bit numbers which are
(in order): C<proc_nr>, C<serial>, C<position>, C<total>.

The units of C<total> are not defined, although for some operations C<total>
may relate in some way to the amount of data to be transferred (eg. in bytes
or megabytes), and C<position> may be the portion which has been
transferred.

The only defined and stable parts of the API are:

=over 4

=item *

The callback can display to the user some type of progress bar or indicator
which shows the ratio of C<position>:C<total>.

=item *

0 E<lt>= C<position> E<lt>= C<total>

=item *

If any progress notification is sent during a call, then a final progress
notification is always sent when C<position> = C<total> (I<unless> the call
fails with an error).

This is to simplify caller code, so callers can easily set the progress
indicator to "100%" at the end of the operation, without requiring special
code to detect this case.

=item *

For some calls we are unable to estimate the progress of the call, but we
can still generate progress messages to indicate activity.  This is known as
"pulse mode", and is directly supported by certain progress bar
implementations (eg. GtkProgressBar).

For these calls, zero or more progress messages are generated with
C<position = 0> and C<total = 1>, followed by a final message with
C<position = total = 1>.

As noted above, if the call fails with an error then the final message may
not be generated.

=back

The callback also receives the procedure number (C<proc_nr>) and serial
number (C<serial>) of the call.  These are only useful for debugging
protocol issues, and the callback can normally ignore them.  The callback
may want to print these numbers in error messages or debugging messages.

If no callback is registered: progress messages are discarded.

=item GUESTFS_EVENT_APPLIANCE (ペイロード形式: メッセージバッファー)

The callback function is called whenever a log message is generated by qemu,
the appliance kernel, guestfsd (daemon), or utility programs.

If the verbose flag (L</guestfs_set_verbose>) is set before launch
(L</guestfs_launch>) then additional debug messages are generated.

If no callback is registered: the messages are discarded unless the verbose
flag is set in which case they are sent to stderr.  You can override the
printing of verbose messages to stderr by setting up a callback.

=item GUESTFS_EVENT_LIBRARY (payload type: message buffer)

The callback function is called whenever a log message is generated by the
library part of libguestfs.

If the verbose flag (L</guestfs_set_verbose>) is set then additional debug
messages are generated.

If no callback is registered: the messages are discarded unless the verbose
flag is set in which case they are sent to stderr.  You can override the
printing of verbose messages to stderr by setting up a callback.

=item GUESTFS_EVENT_TRACE (ペイロード形式: メッセージバッファー)

The callback function is called whenever a trace message is generated.  This
only applies if the trace flag (L</guestfs_set_trace>) is set.

If no callback is registered: the messages are sent to stderr.  You can
override the printing of trace messages to stderr by setting up a callback.

=item GUESTFS_EVENT_ENTER (payload type: function name)

The callback function is called whenever a libguestfs function is entered.

The payload is a string which contains the name of the function that we are
entering (not including C<guestfs_> prefix).

Note that libguestfs functions can call themselves, so you may see many
events from a single call.  A few libguestfs functions do not generate this
event.

If no callback is registered: the event is ignored.

=back

=head3 guestfs_set_event_callback

 int guestfs_set_event_callback (guestfs_h *g,
                                 guestfs_event_callback cb,
                                 uint64_t event_bitmask,
                                 int flags,
                                 void *opaque);

This function registers a callback (C<cb>) for all event classes in the
C<event_bitmask>.

For example, to register for all log message events, you could call this
function with the bitmask C<GUESTFS_EVENT_APPLIANCE|GUESTFS_EVENT_LIBRARY>.
To register a single callback for all possible classes of events, use
C<GUESTFS_EVENT_ALL>.

C<flags> should always be passed as 0.

C<opaque> is an opaque pointer which is passed to the callback.  You can use
it for any purpose.

The return value is the event handle (an integer) which you can use to
delete the callback (see below).

If there is an error, this function returns C<-1>, and sets the error in the
handle in the usual way (see L</guestfs_last_error> etc.)

Callbacks remain in effect until they are deleted, or until the handle is
closed.

In the case where multiple callbacks are registered for a particular event
class, all of the callbacks are called.  The order in which multiple
callbacks are called is not defined.

=head3 guestfs_delete_event_callback

 void guestfs_delete_event_callback (guestfs_h *g, int event_handle);

Delete a callback that was previously registered.  C<event_handle> should be
the integer that was returned by a previous call to
C<guestfs_set_event_callback> on the same handle.

=head3 guestfs_event_callback

 typedef void (*guestfs_event_callback) (
                  guestfs_h *g,
                  void *opaque,
                  uint64_t event,
                  int event_handle,
                  int flags,
                  const char *buf, size_t buf_len,
                  const uint64_t *array, size_t array_len);

This is the type of the event callback function that you have to provide.

The basic parameters are: the handle (C<g>), the opaque user pointer
(C<opaque>), the event class (eg. C<GUESTFS_EVENT_PROGRESS>), the event
handle, and C<flags> which in the current API you should ignore.

The remaining parameters contain the event payload (if any).  Each event may
contain a payload, which usually relates to the event class, but for future
proofing your code should be written to handle any payload for any event
class.

C<buf> and C<buf_len> contain a message buffer (if C<buf_len == 0>, then
there is no message buffer).  Note that this message buffer can contain
arbitrary 8 bit data, including NUL bytes.

C<array> and C<array_len> is an array of 64 bit unsigned integers.  At the
moment this is only used for progress messages.

=head3 EXAMPLE: CAPTURING LOG MESSAGES

One motivation for the generic event API was to allow GUI programs to
capture debug and other messages.  In libguestfs E<le> 1.8 these were sent
unconditionally to C<stderr>.

Events associated with log messages are: C<GUESTFS_EVENT_LIBRARY>,
C<GUESTFS_EVENT_APPLIANCE> and C<GUESTFS_EVENT_TRACE>.  (Note that error
messages are not events; you must capture error messages separately).

Programs have to set up a callback to capture the classes of events of
interest:

 int eh =
   guestfs_set_event_callback
     (g, message_callback,
      GUESTFS_EVENT_LIBRARY|GUESTFS_EVENT_APPLIANCE|
      GUESTFS_EVENT_TRACE,
      0, NULL) == -1)
 if (eh == -1) {
   // 通常の方法でエラー処理します
 }

The callback can then direct messages to the appropriate place.  In this
example, messages are directed to syslog:

 static void
 message_callback (
         guestfs_h *g,
         void *opaque,
         uint64_t event,
         int event_handle,
         int flags,
         const char *buf, size_t buf_len,
         const uint64_t *array, size_t array_len)
 {
   const int priority = LOG_USER|LOG_INFO;
   if (buf_len > 0)
     syslog (priority, "event 0x%lx: %s", event, buf);
 }

=head1 CANCELLING LONG TRANSFERS

Some operations can be cancelled by the caller while they are in progress.
Currently only operations that involve uploading or downloading data can be
cancelled (technically: operations that have C<FileIn> or C<FileOut>
parameters in the generator).

=head2 guestfs_user_cancel

 void guestfs_user_cancel (guestfs_h *g);

C<guestfs_user_cancel> cancels the current upload or download operation.

Unlike most other libguestfs calls, this function is signal safe and thread
safe.  You can call it from a signal handler or from another thread, without
needing to do any locking.

The transfer that was in progress (if there is one) will stop shortly
afterwards, and will return an error.  The errno (see
L</guestfs_last_errno>) is set to C<EINTR>, so you can test for this to find
out if the operation was cancelled or failed because of another error.

No cleanup is performed: for example, if a file was being uploaded then
after cancellation there may be a partially uploaded file.  It is the
caller's responsibility to clean up if necessary.

There are two common places that you might call C<guestfs_user_cancel>.

In an interactive text-based program, you might call it from a C<SIGINT>
signal handler so that pressing C<^C> cancels the current operation.  (You
also need to call L</guestfs_set_pgroup> so that child processes don't
receive the C<^C> signal).

In a graphical program, when the main thread is displaying a progress bar
with a cancel button, wire up the cancel button to call this function.

=head1 プライベートデータ領域

You can attach named pieces of private data to the libguestfs handle, fetch
them by name, and walk over them, for the lifetime of the handle.  This is
called the private data area and is only available from the C API.

データの名前付き部分を接続するには、以下の呼び出しを使用します:

 void guestfs_set_private (guestfs_h *g, const char *key, void *data);

C<key> is the name to associate with this data, and C<data> is an arbitrary
pointer (which can be C<NULL>).  Any previous item with the same key is
overwritten.

You can use any C<key> you want, but your key should I<not> start with an
underscore character.  Keys beginning with an underscore character are
reserved for internal libguestfs purposes (eg. for implementing language
bindings).  It is recommended that you prefix the key with some unique
string to avoid collisions with other users.

ポインターを取り出すには、次を使用します:

 void *guestfs_get_private (guestfs_h *g, const char *key);

I<この関数は推奨されません。> 新しいコードでは、代わりに L</guestfs_vfs_label> を使用してください。

Libguestfs does not try to look at or interpret the C<data> pointer in any
way.  As far as libguestfs is concerned, it need not be a valid pointer at
all.  In particular, libguestfs does I<not> try to free the data when the
handle is closed.  If the data must be freed, then the caller must either
free it before calling L</guestfs_close> or must set up a close callback to
do it (see L</GUESTFS_EVENT_CLOSE>).

To walk over all entries, use these two functions:

 void *guestfs_first_private (guestfs_h *g, const char **key_rtn);

 void *guestfs_next_private (guestfs_h *g, const char **key_rtn);

C<guestfs_first_private> returns the first key, pointer pair ("first" does
not have any particular meaning -- keys are not returned in any defined
order).  A pointer to the key is returned in C<*key_rtn> and the
corresponding data pointer is returned from the function.  C<NULL> is
returned if there are no keys stored in the handle.

C<guestfs_next_private> returns the next key, pointer pair.  The return
value of this function is also C<NULL> is there are no further entries to
return.

Notes about walking over entries:

=over 4

=item *

You must not call C<guestfs_set_private> while walking over the entries.

=item *

The handle maintains an internal iterator which is reset when you call
C<guestfs_first_private>.  This internal iterator is invalidated when you
call C<guestfs_set_private>.

=item *

If you have set the data pointer associated with a key to C<NULL>, ie:

 guestfs_set_private (g, key, NULL);

then that C<key> is not returned when walking.

=item *

C<*key_rtn> is only valid until the next call to C<guestfs_first_private>,
C<guestfs_next_private> or C<guestfs_set_private>.

=back

The following example code shows how to print all keys and data pointers
that are associated with the handle C<g>:

 const char *key;
 void *data = guestfs_first_private (g, &key);
 while (data != NULL)
   {
     printf ("key = %s, data = %p\n", key, data);
     data = guestfs_next_private (g, &key);
   }

More commonly you are only interested in keys that begin with an
application-specific prefix C<foo_>.  Modify the loop like so:

 const char *key;
 void *data = guestfs_first_private (g, &key);
 while (data != NULL)
   {
     if (strncmp (key, "foo_", strlen ("foo_")) == 0)
       printf ("key = %s, data = %p\n", key, data);
     data = guestfs_next_private (g, &key);
   }

If you need to modify keys while walking, then you have to jump back to the
beginning of the loop.  For example, to delete all keys prefixed with
C<foo_>:

  const char *key;
  void *data;
 again:
  data = guestfs_first_private (g, &key);
  while (data != NULL)
    {
      if (strncmp (key, "foo_", strlen ("foo_")) == 0)
        {
          guestfs_set_private (g, key, NULL);
          /* note that 'key' pointer is now invalid, and so is
             the internal iterator */
          goto again;
        }
      data = guestfs_next_private (g, &key);
    }

Note that the above loop is guaranteed to terminate because the keys are
being deleted, but other manipulations of keys within the loop might not
terminate unless you also maintain an indication of which keys have been
visited.

=head1 SYSTEMTAP

The libguestfs C library can be probed using systemtap or DTrace.  This is
true of any library, not just libguestfs.  However libguestfs also contains
static markers to help in probing internal operations.

You can list all the static markers by doing:

 stap -l 'process("/usr/lib*/libguestfs.so.0")
              .provider("guestfs").mark("*")'

B<Note:> These static markers are I<not> part of the stable API and may
change in future versions.

=head2 SYSTEMTAP SCRIPT EXAMPLE

This script contains examples of displaying both the static markers and some
ordinary C entry points:

 global last;
 
 function display_time () {
       now = gettimeofday_us ();
       delta = 0;
       if (last > 0)
             delta = now - last;
       last = now;
 
       printf ("%d (+%d):", now, delta);
 }
 
 probe begin {
       last = 0;
       printf ("ready\n");
 }
 
 /* Display all calls to static markers. */
 probe process("/usr/lib*/libguestfs.so.0")
           .provider("guestfs").mark("*") ? {
       display_time();
       printf ("\t%s %s\n", $$name, $$parms);
 }
 
 /* guestfs_mkfs* 関数へのすべての呼び出しを一覧表示します。 */
 probe process("/usr/lib*/libguestfs.so.0")
           .function("guestfs_mkfs*") ? {
       display_time();
       printf ("\t%s %s\n", probefunc(), $$parms);
 }

The script above can be saved to C<test.stap> and run using the L<stap(1)>
program.  Note that you either have to be root, or you have to add yourself
to several special stap groups.  Consult the systemtap documentation for
more information.

 # stap /tmp/test.stap
 ready

他の端末において、このように guestfish コマンドを実行します:

 guestfish -N fs

In the first terminal, stap trace output similar to this is shown:

 1318248056692655 (+0):	launch_start
 1318248056692850 (+195):       launch_build_appliance_start
 1318248056818285 (+125435):    launch_build_appliance_end
 1318248056838059 (+19774):     launch_run_qemu
 1318248061071167 (+4233108):   launch_end
 1318248061280324 (+209157):    guestfs_mkfs g=0x1024ab0 fstype=0x46116f device=0x1024e60

=begin HTML

<!-- old anchor for the next section --> <a
name="state_machine_and_low_level_event_api"/>

=end HTML

=head1 アーキテクチャー

内部的に、libguestfs は L<qemu(1)>
を使用してアプライアンス（特別な形式の小さな仮想マシン）を実行することにより実装されます。QEMU はメインプログラムの子プロセスとして実行します。

  ___________________
 /                   \
 | main program      |
 |                   |
 |                   |           child process / appliance
 |                   |           __________________________
 |                   |          / qemu                     \
 +-------------------+   RPC    |      +-----------------+ |
 | libguestfs     <--------------------> guestfsd        | |
 |                   |          |      +-----------------+ |
 \___________________/          |      | Linux kernel    | |
                                |      +--^--------------+ |
                                \_________|________________/
                                          |
                                   _______v______
                                  /              \
                                  | Device or    |
                                  | disk image   |
                                  \______________/

The library, linked to the main program, creates the child process and hence
the appliance in the L</guestfs_launch> function.

Inside the appliance is a Linux kernel and a complete stack of userspace
tools (such as LVM and ext2 programs) and a small controlling daemon called
L</guestfsd>.  The library talks to L</guestfsd> using remote procedure
calls (RPC).  There is a mostly one-to-one correspondence between libguestfs
API calls and RPC calls to the daemon.  Lastly the disk image(s) are
attached to the qemu process which translates device access by the
appliance's Linux kernel into accesses to the image.

A common misunderstanding is that the appliance "is" the virtual machine.
Although the disk image you are attached to might also be used by some
virtual machine, libguestfs doesn't know or care about this.  (But you will
care if both libguestfs's qemu process and your virtual machine are trying
to update the disk image at the same time, since these usually results in
massive disk corruption).

=head1 状態マシン

libguestfs は子プロセスをモデル化するために状態マシンを使用します:

                         |
                    guestfs_create
                         |
                         |
                     ____V_____
                    /          \
                    |  CONFIG  |
                    \__________/
                       ^   ^  \
                       |    \  \ guestfs_launch
                       |    _\__V______
                       |   /           \
                       |   | LAUNCHING |
                       |   \___________/
                       |       /
                       |  guestfs_launch
                       |     /
                     __|____V
                    /        \
                    | READY  |
                    \________/

The normal transitions are (1) CONFIG (when the handle is created, but there
is no child process), (2) LAUNCHING (when the child process is booting up),
(3) READY meaning the appliance is up, actions can be issued to, and carried
out by, the child process.

仮想マシンは L</guestfs_kill_subprocess>
により強制停止されるかもしれません。または、いつでも非同期的に停止するかもしれません（例: いくつかの内部エラーのため）、状態を設定 (CONFIG)
に切り戻します。

L</guestfs_add_drive> のような QEMU に対する設定コマンドは、設定 (CONFIG) 状態にあるときのみ発行できます。

The API offers one call that goes from CONFIG through LAUNCHING to READY.
L</guestfs_launch> blocks until the child process is READY to accept
commands (or until some failure or timeout).  L</guestfs_launch> internally
moves the state from CONFIG to LAUNCHING while it is running.

API actions such as L</guestfs_mount> can only be issued when in the READY
state.  These API calls block waiting for the command to be carried out.
There are no non-blocking versions, and no way to issue more than one
command per handle at the same time.

Finally, the child process sends asynchronous messages back to the main
program, such as kernel log messages.  You can register a callback to
receive these messages.

=head1 INTERNALS

=head2 アプライアンスの起動プロセス

このプロセスは進化してきました。そして、進化し続けます。ここの記述は現在のバージョンの libguestfs
にのみ対応していて、参考情報としてのみ提供されます。

以下に関係する段階に従うには libguestfs デバッグを有効にします（環境変数 C<LIBGUESTFS_DEBUG=1> を設定します）。

=over 4

=item アプライアンスを作成します

C<febootstrap-supermin-helper> はカーネル、小さな initrd およびアプライアンスを作成するために呼び出されます。

アプライアンスは C</var/tmp/.guestfs-E<lt>UIDE<gt>> にキャッシュされます（または C<TMPDIR>
を設定していると他の場所です）。

アプライアンスがどのように作成されキャッシュされるかに関する完全な説明は、L<febootstrap(8)> および
L<febootstrap-supermin-helper(8)> マニュアルページを参照してください。

=item QEMU を開始してカーネルを起動します

カーネルを起動するために QEMU が呼び出されます。

=item initrd を実行します

C<febootstrap-supermin-helper> は小さな initrd を構築します。 initrd はアプライアンスではありません。
initrd の目的は、アプライアンス自身がマウントでき開始できるために、十分なカーネルモジュールを読み込むことです。

initrd は C</var/tmp/.guestfs-E<lt>UIDE<gt>/initrd> という cpio アーカイブです。

initrd が起動したとき、カーネルモジュールが読み込まれたことを示すこのようなメッセージが表示されます:

 febootstrap: ext2 mini initrd starting up
 febootstrap: mounting /sys
 febootstrap: internal insmod libcrc32c.ko
 febootstrap: internal insmod crc32c-intel.ko

=item アプライアンスデバイスを検索およびマウントします

The appliance is a sparse file containing an ext2 filesystem which contains
a familiar (although reduced in size) Linux operating system.  It would
normally be called C</var/tmp/.guestfs-E<lt>UIDE<gt>/root>.

The regular disks being inspected by libguestfs are the first devices
exposed by qemu (eg. as C</dev/vda>).

The last disk added to qemu is the appliance itself (eg. C</dev/vdb> if
there was only one regular disk).

Thus the final job of the initrd is to locate the appliance disk, mount it,
and switch root into the appliance, and run C</init> from the appliance.

If this works successfully you will see messages such as:

 febootstrap: picked /sys/block/vdb/dev as root device
 febootstrap: creating /dev/root as block special 252:16
 febootstrap: mounting new root on /root
 febootstrap: chroot
 Starting /init script ...

Note that C<Starting /init script ...> indicates that the appliance's init
script is now running.

=item アプライアンスを初期化します

The appliance itself now initializes itself.  This involves starting certain
processes like C<udev>, possibly printing some debug information, and
finally running the daemon (C<guestfsd>).

=item デーモン

Finally the daemon (C<guestfsd>) runs inside the appliance.  If it runs you
should see:

 verbose daemon enabled

The daemon expects to see a named virtio-serial port exposed by qemu and
connected on the other end to the library.

The daemon connects to this port (and hence to the library) and sends a four
byte message C<GUESTFS_LAUNCH_FLAG>, which initiates the communication
protocol (see below).

=back

=head2 COMMUNICATION PROTOCOL

Don't rely on using this protocol directly.  This section documents how it
currently works, but it may change at any time.

The protocol used to talk between the library and the daemon running inside
the qemu virtual machine is a simple RPC mechanism built on top of XDR (RFC
1014, RFC 1832, RFC 4506).

The detailed format of structures is in C<src/guestfs_protocol.x> (note:
this file is automatically generated).

There are two broad cases, ordinary functions that don't have any C<FileIn>
and C<FileOut> parameters, which are handled with very simple request/reply
messages.  Then there are functions that have any C<FileIn> or C<FileOut>
parameters, which use the same request and reply messages, but they may also
be followed by files sent using a chunked encoding.

=head3 ORDINARY FUNCTIONS (NO FILEIN/FILEOUT PARAMS)

For ordinary functions, the request message is:

 total length (header + arguments,
      but not including the length word itself)
 struct guestfs_message_header (encoded as XDR)
 struct guestfs_<foo>_args (encoded as XDR)

The total length field allows the daemon to allocate a fixed size buffer
into which it slurps the rest of the message.  As a result, the total length
is limited to C<GUESTFS_MESSAGE_MAX> bytes (currently 4MB), which means the
effective size of any request is limited to somewhere under this size.

Note also that many functions don't take any arguments, in which case the
C<guestfs_I<foo>_args> is completely omitted.

The header contains the procedure number (C<guestfs_proc>) which is how the
receiver knows what type of args structure to expect, or none at all.

For functions that take optional arguments, the optional arguments are
encoded in the C<guestfs_I<foo>_args> structure in the same way as ordinary
arguments.  A bitmask in the header indicates which optional arguments are
meaningful.  The bitmask is also checked to see if it contains bits set
which the daemon does not know about (eg. if more optional arguments were
added in a later version of the library), and this causes the call to be
rejected.

The reply message for ordinary functions is:

 total length (header + ret,
      but not including the length word itself)
 struct guestfs_message_header (encoded as XDR)
 struct guestfs_<foo>_ret (encoded as XDR)

As above the C<guestfs_I<foo>_ret> structure may be completely omitted for
functions that return no formal return values.

As above the total length of the reply is limited to C<GUESTFS_MESSAGE_MAX>.

In the case of an error, a flag is set in the header, and the reply message
is slightly changed:

 total length (header + error,
      but not including the length word itself)
 struct guestfs_message_header (encoded as XDR)
 struct guestfs_message_error (encoded as XDR)

C<guestfs_message_error> の構造は、文字列としてエラーメッセージを含みます。

=head3 FUNCTIONS THAT HAVE FILEIN PARAMETERS

A C<FileIn> parameter indicates that we transfer a file I<into> the guest.
The normal request message is sent (see above).  However this is followed by
a sequence of file chunks.

 total length (header + arguments,
      but not including the length word itself,
      and not including the chunks)
 struct guestfs_message_header (encoded as XDR)
 struct guestfs_<foo>_args (encoded as XDR)
 sequence of chunks for FileIn param #0
 sequence of chunks for FileIn param #1 etc.

The "sequence of chunks" is:

 length of chunk (not including length word itself)
 struct guestfs_chunk (encoded as XDR)
 length of chunk
 struct guestfs_chunk (encoded as XDR)
   ...
 length of chunk
 struct guestfs_chunk (with data.data_len == 0)

The final chunk has the C<data_len> field set to zero.  Additionally a flag
is set in the final chunk to indicate either successful completion or early
cancellation.

At time of writing there are no functions that have more than one FileIn
parameter.  However this is (theoretically) supported, by sending the
sequence of chunks for each FileIn parameter one after another (from left to
right).

Both the library (sender) I<and> the daemon (receiver) may cancel the
transfer.  The library does this by sending a chunk with a special flag set
to indicate cancellation.  When the daemon sees this, it cancels the whole
RPC, does I<not> send any reply, and goes back to reading the next request.

The daemon may also cancel.  It does this by writing a special word
C<GUESTFS_CANCEL_FLAG> to the socket.  The library listens for this during
the transfer, and if it gets it, it will cancel the transfer (it sends a
cancel chunk).  The special word is chosen so that even if cancellation
happens right at the end of the transfer (after the library has finished
writing and has started listening for the reply), the "spurious" cancel flag
will not be confused with the reply message.

This protocol allows the transfer of arbitrary sized files (no 32 bit
limit), and also files where the size is not known in advance (eg. from
pipes or sockets).  However the chunks are rather small
(C<GUESTFS_MAX_CHUNK_SIZE>), so that neither the library nor the daemon need
to keep much in memory.

=head3 FUNCTIONS THAT HAVE FILEOUT PARAMETERS

The protocol for FileOut parameters is exactly the same as for FileIn
parameters, but with the roles of daemon and library reversed.

 total length (header + ret,
      but not including the length word itself,
      and not including the chunks)
 struct guestfs_message_header (encoded as XDR)
 struct guestfs_<foo>_ret (encoded as XDR)
 sequence of chunks for FileOut param #0
 sequence of chunks for FileOut param #1 etc.

=head3 INITIAL MESSAGE

When the daemon launches it sends an initial word (C<GUESTFS_LAUNCH_FLAG>)
which indicates that the guest and daemon is alive.  This is what
L</guestfs_launch> waits for.

=head3 PROGRESS NOTIFICATION MESSAGES

The daemon may send progress notification messages at any time.  These are
distinguished by the normal length word being replaced by
C<GUESTFS_PROGRESS_FLAG>, followed by a fixed size progress message.

The library turns them into progress callbacks (see
L</GUESTFS_EVENT_PROGRESS>) if there is a callback registered, or discards
them if not.

The daemon self-limits the frequency of progress messages it sends (see
C<daemon/proto.c:notify_progress>).  Not all calls generate progress
messages.

=head1 LIBGUESTFS VERSION NUMBERS

Since April 2010, libguestfs has started to make separate development and
stable releases, along with corresponding branches in our git repository.
These separate releases can be identified by version number:

                 偶数は安定版: 1.2.x, 1.4.x, ...
       .-------- 奇数は開発版: 1.3.x, 1.5.x, ...
       |
       v
 1  .  3  .  5
 ^           ^
 |           |
 |           `-------- サブバージョン
 |
 `------ ABI を変更しないので、必ず '1' です

このように "1.3.5" は開発ブランチ "1.3" の 5 番目のアップデートです。

As time passes we cherry pick fixes from the development branch and backport
those into the stable branch, the effect being that the stable branch should
get more stable and less buggy over time.  So the stable releases are ideal
for people who don't need new features but would just like the software to
work.

バックポートする変更に対する私たちの基準は次のとおりです:

=over 4

=item *

コードに何も影響しないドキュメントの変更は、ドキュメントが安定版にない将来の機能を参照していなければ、バックポートされます。

=item *

議論の余地がなく、明らかな問題を修正する、十分にテストされたバグ修正はバックポートされます。

=item *

Simple rearrangements of code which shouldn't affect how it works get
backported.  This is so that the code in the two branches doesn't get too
far out of step, allowing us to backport future fixes more easily.

=item *

We I<don't> backport new features, new APIs, new tools etc, except in one
exceptional case: the new feature is required in order to implement an
important bug fix.

=back

A new stable branch starts when we think the new features in development are
substantial and compelling enough over the current stable branch to warrant
it.  When that happens we create new stable and development versions 1.N.0
and 1.(N+1).0 [N is even].  The new dot-oh release won't necessarily be so
stable at this point, but by backporting fixes from development, that branch
will stabilize over time.

=head1 EXTENDING LIBGUESTFS

=head2 ADDING A NEW API ACTION

Large amounts of boilerplate code in libguestfs (RPC, bindings,
documentation) are generated, and this makes it easy to extend the
libguestfs API.

To add a new API action there are two changes:

=over 4

=item 1.

You need to add a description of the call (name, parameters, return type,
tests, documentation) to C<generator/generator_actions.ml>.

There are two sorts of API action, depending on whether the call goes
through to the daemon in the appliance, or is serviced entirely by the
library (see L</ARCHITECTURE> above).  L</guestfs_sync> is an example of the
former, since the sync is done in the appliance.  L</guestfs_set_trace> is
an example of the latter, since a trace flag is maintained in the handle and
all tracing is done on the library side.

Most new actions are of the first type, and get added to the
C<daemon_functions> list.  Each function has a unique procedure number used
in the RPC protocol which is assigned to that action when we publish
libguestfs and cannot be reused.  Take the latest procedure number and
increment it.

For library-only actions of the second type, add to the
C<non_daemon_functions> list.  Since these functions are serviced by the
library and do not travel over the RPC mechanism to the daemon, these
functions do not need a procedure number, and so the procedure number is set
to C<-1>.

=item 2.

Implement the action (in C):

For daemon actions, implement the function C<do_E<lt>nameE<gt>> in the
C<daemon/> directory.

For library actions, implement the function C<guestfs__E<lt>nameE<gt>>
(note: double underscore) in the C<src/> directory.

In either case, use another function as an example of what to do.

=back

After making these changes, use C<make> to compile.

Note that you don't need to implement the RPC, language bindings, manual
pages or anything else.  It's all automatically generated from the OCaml
description.

=head2 ADDING TESTS FOR AN API ACTION

You can supply zero or as many tests as you want per API call.  The tests
can either be added as part of the API description
(C<generator/generator_actions.ml>), or in some rarer cases you may want to
drop a script into C<tests/*/>.  Note that adding a script to C<tests/*/> is
slower, so if possible use the first method.

The following describes the test environment used when you add an API test
in C<generator_actions.ml>.

テスト環境は 4 個のブロックデバイスを持ちます:

=over 4

=item C</dev/sda> 500MB

テスト用の一般的なブロックデバイス。

=item C</dev/sdb> 50MB

C</dev/sdb1> はファイルシステムの書き込み操作をテストするために使用される ext2 ファイルシステムです。

=item C</dev/sdc> 10MB

2 つのブロックデバイスが必要となるいくつかのテストにおいて使用されます。

=item C</dev/sdd>

固定的な内容を持つ ISO (C<images/test.iso> 参照)。

=back

To be able to run the tests in a reasonable amount of time, the libguestfs
appliance and block devices are reused between tests.  So don't try testing
L</guestfs_kill_subprocess> :-x

Each test starts with an initial scenario, selected using one of the
C<Init*> expressions, described in C<generator/generator_types.ml>.  These
initialize the disks mentioned above in a particular way as documented in
C<generator_types.ml>.  You should not assume anything about the previous
contents of other disks that are not initialized.

You can add a prerequisite clause to any individual test.  This is a
run-time check, which, if it fails, causes the test to be skipped.  Useful
if testing a command which might not work on all variations of libguestfs
builds.  A test that has prerequisite of C<Always> means to run
unconditionally.

In addition, packagers can skip individual tests by setting environment
variables before running C<make check>.

 SKIP_TEST_<CMD>_<NUM>=1

例: C<SKIP_TEST_COMMAND_3=1> は L</guestfs_command> のテスト #3 をスキップします。

または:

 SKIP_TEST_<CMD>=1

例: C<SKIP_TEST_ZEROFREE=1> はすべての L</guestfs_zerofree> テストをスキップします。

Packagers can run only certain tests by setting for example:

 TEST_ONLY="vfs_type zerofree"

これらの環境変数がどのように機能するかに関する詳細は C<tests/c-api/tests.c> を参照してください。

=head2 DEBUGGING NEW API ACTIONS

Test new actions work before submitting them.

新しいコマンドを試すために guestfish を使うことができます。

Debugging the daemon is a problem because it runs inside a minimal
environment.  However you can fprintf messages in the daemon to stderr, and
they will show up if you use C<guestfish -v>.

=head2 FORMATTING CODE AND OTHER CONVENTIONS

Our C source code generally adheres to some basic code-formatting
conventions.  The existing code base is not totally consistent on this
front, but we do prefer that contributed code be formatted similarly.  In
short, use spaces-not-TABs for indentation, use 2 spaces for each
indentation level, and other than that, follow the K&R style.

If you use Emacs, add the following to one of one of your start-up files
(e.g., ~/.emacs), to help ensure that you get indentation right:

 ;;; In libguestfs, indent with spaces everywhere (not TABs).
 ;;; Exceptions: Makefile and ChangeLog modes.
 (add-hook 'find-file-hook
     '(lambda () (if (and buffer-file-name
                          (string-match "/libguestfs\\>"
                              (buffer-file-name))
                          (not (string-equal mode-name "Change Log"))
                          (not (string-equal mode-name "Makefile")))
                     (setq indent-tabs-mode nil))))
 
 ;;; When editing C sources in libguestfs, use this style.
 (defun libguestfs-c-mode ()
   "C mode with adjusted defaults for use with libguestfs."
   (interactive)
   (c-set-style "K&R")
   (setq c-indent-level 2)
   (setq c-basic-offset 2))
 (add-hook 'c-mode-hook
           '(lambda () (if (string-match "/libguestfs\\>"
                               (buffer-file-name))
                           (libguestfs-c-mode))))

コンパイル時に警告を有効にします（そして、これは見つけた問題をすべて修正します）:

 ./configure --enable-gcc-warnings

有用なターゲットは次のとおりです:

 make syntax-check  # C コードの構文を確認します
 make check         # テストスイートを実行します

=head2 DAEMON CUSTOM PRINTF FORMATTERS

In the daemon code we have created custom printf formatters C<%Q> and C<%R>,
which are used to do shell quoting.

=over 4

=item %Q

シンプルなシェルクオート文字列。すべての空白と他のシェル文字がエスケープされます。

=item %R

Same as C<%Q> except the string is treated as a path which is prefixed by
the sysroot.

=back

例:

 asprintf (&cmd, "cat %R", path);

C<cat /sysroot/some\ path\ with\ spaces> を生成します

I<Note:> Do I<not> use these when you are passing parameters to the
C<command{,r,v,rv}()> functions.  These parameters do NOT need to be quoted
because they are not passed via the shell (instead, straight to exec).  You
probably want to use the C<sysroot_path()> function however.

=head2 新しい API アクションの提出方法

パッチをメーリングリストに提出します: L<http://www.redhat.com/mailman/listinfo/libguestfs> および
L<rjones@redhat.com> (Cc)。

=head2 国際化 (i18n) サポート

We support i18n (gettext anyhow) in the library.

However many messages come from the daemon, and we don't translate those at
the moment.  One reason is that the appliance generally has all locale files
removed from it, because they take up a lot of space.  So we'd have to readd
some of those, as well as copying our PO files into the appliance.

Debugging messages are never translated, since they are intended for the
programmers.

=head2 ソースコードのサブディレクトリー

=over 4

=item C<align>

L<virt-alignment-scan(1)> のコマンドおよびドキュメント。

=item C<appliance>

libguestfs アプライアンス、スクリプトなどを構築します。

=item C<cat>

L<virt-cat(1)>, L<virt-filesystems(1)> および L<virt-ls(1)> のコマンドおよびドキュメント。

=item C<contrib>

外部の貢献、実験的な部分です。

=item C<daemon>

The daemon that runs inside the libguestfs appliance and carries out
actions.

=item C<df>

L<virt-df(1)> のコマンドおよびドキュメント。

=item C<edit>

L<virt-edit(1)> のコマンドおよびドキュメント。

=item C<examples>

C API のコード例。

=item C<fish>

L<guestfish(1)>, the command-line shell, and various shell scripts built on
top such as L<virt-copy-in(1)>, L<virt-copy-out(1)>, L<virt-tar-in(1)>,
L<virt-tar-out(1)>.

=item C<format>

L<virt-format(1)> のコマンドおよびドキュメント。

=item C<fuse>

L<guestmount(1)>, FUSE (userspace filesystem) built on top of libguestfs.

=item C<generator>

The crucially important generator, used to automatically generate large
amounts of boilerplate C code for things like RPC and bindings.

=item C<inspector>

L<virt-inspector(1)>, 仮想マシンイメージ検査ツール。

=item C<logo>

Logo used on the website.  The fish is called Arthur by the way.

=item C<m4>

autoconf により使用される M4 マクロ。

=item C<po>

Translations of simple gettext strings.

=item C<po-docs>

The build infrastructure and PO files for translations of manpages and POD
files.  Eventually this will be combined with the C<po> directory, but that
is rather complicated.

=item C<rescue>

L<virt-rescue(1)> のコマンドおよびドキュメント。

=item C<resize>

L<virt-resize(1)> のコマンドおよびドキュメント。

=item C<sparsify>

L<virt-sparsify(1)> のコマンドおよびドキュメント。

=item C<src>

C ライブラリーのソースコード。

=item C<sysprep>

L<virt-sysprep(1)> command and documentation.

=item C<test-tool>

Test tool for end users to test if their qemu/kernel combination will work
with libguestfs.

=item C<tests>

テストします。

=item C<tools>

Command line tools written in Perl (L<virt-win-reg(1)> and many others).

=item C<csharp>

=item C<erlang>

=item C<gobject>

=item C<haskell>

=item C<java>

=item C<ocaml>

=item C<php>

=item C<perl>

=item C<python>

=item C<ruby>

言語バインディング。

=back

=head2 MAKING A STABLE RELEASE

When we make a stable release, there are several steps documented here.  See
L</LIBGUESTFS VERSION NUMBERS> for general information about the stable
branch policy.

=over 4

=item *

Check C<make && make check> works on at least Fedora, Debian and Ubuntu.

=item *

Finalize RELEASE-NOTES.

=item *

ロードマップを更新します。

=item *

C<src/api-support/update-from-tarballs.sh> を実行します。

=item *

Transifex からのプッシュおよびプル。

次を実行します:

 tx push -s

最新の POT ファイルを Transifex にプッシュします。そして、次を実行します:

 ./tx-pull.sh

これは最新の翻訳された C<*.po> ファイルを取り出すためのラッパーです。

=item *

L<http://libguestfs.org/download> の下に新しい安定版および開発版のディレクトリーを作成します。

=item *

git に分岐を作成します:

 git tag -a 1.XX.0 -m "Version 1.XX.0 (安定版)"
 git tag -a 1.YY.0 -m "Version 1.YY.0 (開発版)"
 git branch stable-1.XX
 git push origin tag 1.XX.0 1.YY.0 stable-1.XX

=back

=head1 制限

=head2 プロトコル制限

Internally libguestfs uses a message-based protocol to pass API calls and
their responses to and from a small "appliance" (see L</INTERNALS> for
plenty more detail about this).  The maximum message size used by the
protocol is slightly less than 4 MB.  For some API calls you may need to be
aware of this limit.  The API calls which may be affected are individually
documented, with a link back to this section of the documentation.

A simple call such as L</guestfs_cat> returns its result (the file data) in
a simple string.  Because this string is at some point internally encoded as
a message, the maximum size that it can return is slightly under 4 MB.  If
the requested file is larger than this then you will get an error.

In order to transfer large files into and out of the guest filesystem, you
need to use particular calls that support this.  The sections L</UPLOADING>
and L</DOWNLOADING> document how to do this.

FUSE ファイルシステムサポート (L<guestmount(1)>) を使用してディスクイメージをマウントすることも検討できます。

=head2 MAXIMUM NUMBER OF DISKS

When using virtio disks (the default) the current limit is B<25> disks.

Virtio itself consumes 1 virtual PCI slot per disk, and PCI is limited to 31
slots.  However febootstrap only understands disks with names C</dev/vda>
through C</dev/vdz> (26 letters) and it reserves one disk for its own
purposes.

We are working to substantially raise this limit in future versions but it
requires complex changes to qemu.

In future versions of libguestfs it should also be possible to "hot plug"
disks (add and remove disks after calling L</guestfs_launch>).  This also
requires changes to qemu.

=head2 ディスクあたりの最大パーティション数

virtio はディスクあたりの最大パーティション数を B<15> に制限します。

これはマイナーデバイス番号のために 4 ビットを予約しているからです（つまり C</dev/vda>、および C</dev/vda1> から
C</dev/vda15> まで）。

15 よりも多くのパーティションを持つディスクを接続すると、追加のパーティションは libguestfs により無視されます。

=head2 ディスクの最大容量

制限はおそらく 2**63-1 から 2**64-1 バイトの間です。

We have tested block devices up to 1 exabyte (2**60 or
1,152,921,504,606,846,976 bytes) using sparse files backed by an XFS host
filesystem.

Although libguestfs probably does not impose any limit, the underlying host
storage will.  If you store disk images on a host ext4 filesystem, then the
maximum size will be limited by the maximum ext4 file size (currently 16
TB).  If you store disk images as host logical volumes then you are limited
by the maximum size of an LV.

For the hugest disk image files, we recommend using XFS on the host for
storage.

=head2 パーティションの最大容量

The MBR (ie. classic MS-DOS) partitioning scheme uses 32 bit sector
numbers.  Assuming a 512 byte sector size, this means that MBR cannot
address a partition located beyond 2 TB on the disk.

It is recommended that you use GPT partitions on disks which are larger than
this size.  GPT uses 64 bit sector numbers and so can address partitions
which are theoretically larger than the largest disk we could support.

=head2 ファイルシステム、ファイル、ディレクトリーの最大容量

This depends on the filesystem type.  libguestfs itself does not impose any
known limit.  Consult Wikipedia or the filesystem documentation to find out
what these limits are.

=head2 MAXIMUM UPLOAD AND DOWNLOAD

The API functions L</guestfs_upload>, L</guestfs_download>,
L</guestfs_tar_in>, L</guestfs_tar_out> and the like allow unlimited sized
uploads and downloads.

=head2 INSPECTION LIMITS

The inspection code has several arbitrary limits on things like the size of
Windows Registry hive it will read, and the length of product name.  These
are intended to stop a malicious guest from consuming arbitrary amounts of
memory and disk space on the host, and should not be reached in practice.
See the source code for more information.

=head1 環境変数

=over 4

=item FEBOOTSTRAP_KERNEL

=item FEBOOTSTRAP_MODULES

These two environment variables allow the kernel that libguestfs uses in the
appliance to be selected.  If C<$FEBOOTSTRAP_KERNEL> is not set, then the
most recent host kernel is chosen.  For more information about kernel
selection, see L<febootstrap-supermin-helper(8)>.  This feature is only
available in febootstrap E<ge> 3.8.

=item LIBGUESTFS_APPEND

仮想マシンのカーネルに追加のオプションを渡します。

=item LIBGUESTFS_DEBUG

Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages.  This has the same
effect as calling C<guestfs_set_verbose (g, 1)>.

=item LIBGUESTFS_MEMSIZE

Set the memory allocated to the qemu process, in megabytes.  For example:

 LIBGUESTFS_MEMSIZE=700

=item LIBGUESTFS_PATH

Set the path that libguestfs uses to search for a supermin appliance.  See
the discussion of paths in section L</PATH> above.

=item LIBGUESTFS_QEMU

Set the default qemu binary that libguestfs uses.  If not set, then the qemu
which was found at compile time by the configure script is used.

上の L</QEMU WRAPPERS> 参照。

=item LIBGUESTFS_TRACE

コマンドトレースを有効にするには C<LIBGUESTFS_TRACE=1> を設定します。これは C<guestfs_set_trace (g,
1)> の呼び出しと同じ効果があります。

=item TMPDIR

一時ディレクトリーの場所です。初期値は C</tmp> です。初期値が C</var/tmp> であるキャッシュされた supermin
アプライアンスは除きます。

libguestfs が supermin
アプライアンスを使用するようコンパイルされていると、本当のアプライアンスがこのディレクトリーにキャッシュされ、同じ EUID
に属するすべてのハンドル間で共有されます。 C</var/tmp> が十分に大きくない場合に使用する他のディレクトリーを設定するために
C<$TMPDIR> を使用できます。

=back

=head1 関連項目

L<guestfs-examples(3)>, L<guestfs-erlang(3)>, L<guestfs-java(3)>,
L<guestfs-ocaml(3)>, L<guestfs-perl(3)>, L<guestfs-python(3)>,
L<guestfs-ruby(3)>, L<guestfish(1)>, L<guestmount(1)>,
L<virt-alignment-scan(1)>, L<virt-cat(1)>, L<virt-copy-in(1)>,
L<virt-copy-out(1)>, L<virt-df(1)>, L<virt-edit(1)>, L<virt-filesystems(1)>,
L<virt-format(1)>, L<virt-inspector(1)>, L<virt-list-filesystems(1)>,
L<virt-list-partitions(1)>, L<virt-ls(1)>, L<virt-make-fs(1)>,
L<virt-rescue(1)>, L<virt-resize(1)>, L<virt-sparsify(1)>,
L<virt-sysprep(1)>, L<virt-tar(1)>, L<virt-tar-in(1)>, L<virt-tar-out(1)>,
L<virt-win-reg(1)>, L<guestfs-faq(1)>, L<guestfs-performance(1)>,
L<guestfs-testing(1)>, L<libguestfs-test-tool(1)>,
L<libguestfs-make-fixed-appliance(1)>, L<febootstrap(1)>,
L<febootstrap-supermin-helper(8)>, L<qemu(1)>, L<hivex(3)>, L<stap(1)>,
L<http://libguestfs.org/>.

同じ目的を持つツール: L<fdisk(8)>, L<parted(8)>, L<kpartx(8)>, L<lvm(8)>,
L<disktype(1)>.

=head1 バグ

libguestfs のバグの一覧を取得するには、このリンクを使用します:

L<https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools>

libguestfs の新しいバグを報告するには、このリンクを使用します:

L<https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools>

バグを報告するとき、確認してください:

=over 4

=item *

バグはまだ報告されていません。

=item *

あなたはいま最近のバージョンを試しています。

=item *

Describe the bug accurately, and give a way to reproduce it.

=item *

Run libguestfs-test-tool and paste the B<complete, unedited> output into the
bug report.

=back

=head1 著者

Richard W.M. Jones (C<rjones at redhat dot com>)

=head1 COPYRIGHT

Copyright (C) 2009-2012 Red Hat Inc.  L<http://libguestfs.org/>

This library is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
for more details.

You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA