mach - make a chroot
--------------------

0. IMPORTANT
------------
If you're on Fedora Core 2, and want to build for older targets,
MAKE SURE you turn off vdso's by doing

sysctl -w kernel.vdso=0

before using mach.
You can add an entry to /etc/sysctl.conf to make this more permanent.

1. WHAT IS IT ?
---------------
mach allows you to set up clean roots from scratch for any distribution or
distribution variation supported.

This clean build root can be used for several goals :
- making clean packages
- set up chroots for services to run it
- make disk images of clean roots (for example for UML)

mach uses python.
This mach is not to be confused with the microkernel of the same name.
If you can't tell the difference between this mach and that mach from a
cursory look then neither is for you.

Currently, mach works for rpm-based distributions that can work with apt
for rpm - hopefully this will be extended to other types of package manager
as well.

2. WHAT DISTROS ARE SUPPORTED ?
-------------------------------
Included at this moment is the necessary information to set up :

Fedora development
  - Core
  - with Extras
  - with rpm.livna.org

Fedora 4, 5, 6
  - Core
  - updated
  - with Extras
  - with rpm.livna.org
  - with FreshRPMS
  - with JPackage

Fedora 1, 2, 3
  - Core
  - updated
  - with fedora.us stable, testing and unstable/extras
  - with rpm.livna.org stable, testing and unstable
  - with FreshRPMS
  - with JPackage

Red Hat 8.0 and 9
  - standard
  - updated
  - with fedora.us stable, testing and unstable
  - with rpm.livna.org stable, testing and unstable
  - with FreshRPMS
  - with JPackage

Red Hat 7.2 and 7.3
  - standard
  - updated
  - with FreshRPMS
  - with JPackage

Red Hat 7.0 and 7.1
  - standard
  - updated
  - with FreshRPMS

CentOS 4
  - standard
  - updated
  - with addons
  - with contrib
  - with csgfs
  - with extras
  - with centosplus
  - with Fedora Extras rebuilds
  - with JPackage

Dave/Dina
  - fridge
  - oven

Conectiva 9
  - standard
  - updated

SuSE 8.1, 8.2 and 9.0
  - base
  - updated

Yellowdog 2.3 and 3.0
  - standard
  - updated
  - with FreshRPMS

Some handy features of mach include
  - "caching" of downloaded packages using the build hosts's apt
    the build root
  - ensures clean packages by reverting to the base set of build packages
  - uses apt to resolve dependencies
  - parsing of BuildRequires to install necessary packages for building
  - build ordering when doing multiple builds
  - support for flavours of distribution
  - multiple build roots
  - locking of buildroot to avoid concurrent builds
  - optional signing of built packages

3. REQUIREMENTS
---------------
- A Linux kernel that can do bind mounts (>= 2.2.0 if I'm correct)
- rpm (>= 4.1 + gpg and cpio if you want GPG)
- python
- apt >= 0.5.5cnc2 or yum
- sudo
- lots of disk space
- good faith

4. GETTING STARTED - RPM INSTALL
--------------------------------
- The easiest way to install mach is to just install the RPM.
- After installing, you need to add all users that are going to build through
  mach to the "mach" group in /etc/group, and (possibly) log out and log back
  in so that this change gets registered.  You can check if your user
  is in this group by trying "groups (user)"

5. GETTING STARTED - SOURCE INSTALL
-----------------------------------
- If you insist on running from source, do
  ./configure
  make
  make install

  as root.

- you have to setuid the mach-helper binary.
  chmod u+s $(prefix)/sbin/mach-helper

- do not start to tweak stuff all in the source code just yet; mach is picky
  about its setup if you start to hack it.

6. SETTING IT UP
----------------
- configuration files are stored in $(sysconfdir)/mach
  dist contains the list of packages for each distro target, as well
  as download locations for various packages.
  conf contains configuration data, like hosts and resolv.conf files

- It is advised you do not hand-edit these files.  Instead, you can
  override any configuration variable by putting it in
  ~/.machrc

- you can choose between using apt and yum by setting
  config['installer'] = 'yum'
  or
  config['installer'] = 'apt-get'
  in .machrc.

  Each time you change this, you will have to clean up your roots and
  repopulate them.

- you can add dist-specific configurations by creating a dict in ~/.machrc
  It is advised that you create at least a files dict containing
  /etc/resolv.conf and /etc/hosts.

  For example, I have in my .machrc:

config['files'] = {
  '/etc/hosts': '''
127.0.0.1 mach.onshuis onzenbak
''',
  '/etc/resolv.conf': '''
nameserver 127.0.0.1
nameserver 157.193.40.42
search onshuis
'''
}

config['script-success'] = "mach-collect"

This ensures that all packages appear to be built on the host mach.onshuis,
and ensures that it can look up hosts through localhost DNS and one outside
DNS.
Also, after a successful build it will run the mach-collect script with
the built directory as a parameter.

7. USING IT
-----------
- run mach --help for a list of commands you can use.
- Now for the actual work.  If everything is configured properly, you can now
  do
    mach setup base
  and a base root for the default distribution should be created for you.
  run
    mach chroot
  and poke around a little.

- To build a package based on a .spec file, run
  mach build (spec file name)

  If the Source: and Patch: lines contain a proper URL, mach will automatically
  download them and build the package.

- To build a package from a .src.rpm file, run
  mach rebuild (src.rpm)
  You can specify an http:// or ftp:// file here, and it will be downloaded
  and built automatically.

- If the build fails because it needs other packages to build and they weren't
  mentioned in the spec file, you can either:
  - change the spec file and add the BuildRequires:
  - install the packages through mach
       mach apt-get -y install (requires)
    and run the build again, with the -k option (for "keep packages")

- You can build multiple spec files or src.rpms, just try
       mach build *.spec
  or
       mach build *.src.rpm

- To clean the buildroot, run
    mach clean

8. SECURITY
-----------
- By nature mach needs root privileges for some of its operations.
  All operations that it needs this for are done through the mach-helper
  binary, which is suid.  The source code for this binary is deliberately
  kept both simple and very minimal.  The goal here is to make it absolutely
  clear what mach can and cannot do as root.
- If you find any security problems with this, PLEASE let me know.  I don't
  have a lot of experience with secure programming and can use help there.

9. TIPS & TRICKS
----------------
- mach tries to adhere to the FHS.  It uses a lot of disk space by nature.
  You might not have as much space as you would like.  Since security needs
  to be tight, mach-helper is very strict about this location.  A good
  solution for this is to use bind mounts.  For example, I have in my
  /etc/fstab file:
  /home/mach/roots /var/lib/mach/roots auto bind,defaults 0 0
  which causes /home/mach/roots on my big home disk to be mounted again
  on /var/lib/mach/roots.

- mach uses the host's rpm binary to manipulate the database inside the root.
  A lot of fiddling went into this; I could find of no other way to guarantee
  it works reliably for all target platforms.
  As a side effect, you will have to manipulate the target's rpm database
  using rpm and apt from outside the host.
  The easiest way to do this is to use mach to operate on it; for example,
  mach rpm -Uhv (rpm) will install the given rpm in the target's system.

- to build kernel modules or other packages that BuildRequire the kernel
  or kernel-source rpms, you need to manually install the kernel and
  kernel-source packages with the correct version.
  As an example:
  mach -r f1fs apt-get -y install kernel-source#2.4.22-1.2115.nptl
  to install release 1.2115.ntpl of version 2.4.22
  It is best to first try building your .spec file so that the buildroot
  gets restored.  After that, install the kernel packages.  Then, rerun
  the build with -k (to keep packages in the buildroot) and the build should
  succeed.

- SELINUX:
  When using an SELINUX-enabled host, a whole range of things can fail.
  For example, creating an FC2 target on an FC3 host fails when installing
  packages.
  I've added a library that gets preloaded to override selinux, which allows
  most packages to be installed.

10. BUGS
--------
- rpm 4.1 included with Red hat 8.0 has a few race condition bugs which
  can cause rpm to hang.  If this happens, you should kill -9 the stalling
  rpm process, chroot into the root, run "rm -rf /var/lib/rpm/__*" and retry.
  had given.
  I'm interested on feedback running mach on RH8.0, I have no such system
  around anymore.
- for now, report them to me personally at thomas (at) apestaart (dot) org
- mounting /proc into the root system can cause problems.  For example,
  removing openssh-server from the root will cause it to kill your build host's
  ssh server, since it gets the pid from proc.  This isn't what you want to
  have happen if the server is not somewhere in your physical neighbourhood.
  This is the reason why openssh-server is listed in the base install.

11. MAILING LIST
----------------
A mailing list has been set up for discussion of mach use and development.
Check http://lists.sourceforge.net/lists/listinfo/mach-devel for information.
The list is low-volume.

12. ADDING A DISTRIBUTION
-------------------------
- Check the distribution files in $sysconfdir/dist.d and copy one.
- Make sure the download locations you reference are specified in location.

- Base packages: list them in the packages[dist] dict under 'base'.
  You can then test by trying to set up this root,
  See if the installation of base packages works well by doing
  mach -r (dist) setup base

13. DISCLAIMER
--------------
mach is offered under the GPL without any warranty whatsoever.
Let me know where the documentation is lacking, so I can improve on that.