Making and testing RedHat rpms for ntop
Burton M. Strauss III <Burton@ntopsupport.com>
June 2002 / April 2005

===============================================
==== W a r n i n g ============================
===============================================

First off, this is information on how I personally create
rpms for ntop.  It's actually quite simple, but some of
the details will refer to how-tos for other programs.

I use a PIII-800 w/ 128 MB of RAM, named "tigger", which is 
running RedHat 7.2 updated to be reasonably current with 
various packages.  tigger is also my ntop development machine.
All of which is irrelevant for the purposes of creating rpms!

NB: Jul2002 - I upgraded to 384MB - found a cheap 256MB DIMM.
    Performance is a lot better, but nothing really changes.

NB: Apr2005 - Tigger is now dual P3-1000 (SMP) w 832MB of RAM
    running Fedora Core 2.

The underlying platform is still largely irrelevant.


You have THREE basic choices...

1) UML (which I used for 2.1 and earlier)
2) buildmeister (which I used through 3.0)
3) VPC (3.1 and following)

Most of the UML setup was done by trial and error - there may be
a better way.  But it worked well enough for the purpose.

However, I don't always know what I did or how I got it
to work.  If you have questions about rpm or user mode 
linux, don't ask on the ntop lists, ask the rpm or uml 
people!

Also - one real warning... 

     REMEMBER WHICH MACHINE YOU ARE ON when issuing commands!

   It's likely that the rpm won't build right on the underlying
   (real) computer - I once spent three hours trying to (re)install
   things and fixing things because I was trying to build on
   tigger, not ur-tigger!

   ALSO:

       DO NOT SHUTDOWN THE REAL MACHINE THINKING IT IS THE UML MACHINE!

   It causes BAD things like file system corruption to the uml machines!


        Trust me on both of these...

I have not updated the UML instructions since 2.1 days.  But it you go this
route, all of the changes in ntop on a native machine still apply.

==============================================================================================
==== U M L ===================================================================================
==============================================================================================

===============================================
==== E n v i r o n m e n t ====================
===============================================

Building rpms works best if you are running as root.  And on
a system without complications (other services running, etc).
Accordingly, I've used User Mode Linux (uml), which is 
available at

     http://user-mode-linux.sourceforge.net/

On tigger, I created two uml machines, called ur-tigger and
ur-tigger2.  Both are RedHat 7.2 machines - just follow the 
uml instructions.  You may find it easier to use the prebuilt
pristine filesystems available at that site.  I did.

I found that I had trouble with the rpm database, and I rebuilt
it using this procedure:

http://hermes.afaa.asso.fr/users/pascal/linux/rpm-rebuilddb

But you should be able to download a working, pristine version
and not have the problem.

I then stripped them down so that ur-tigger is really just
a development machine - no extra services (it runs ssh and
the development tools).  And ur-tigger2 is a basic user
machine, such as one might install ntop on.

Using uml and only 128MB of ram, but with a PIII-800, it's not 
fast, but it's certainly good enough.  I start ur-tigger,
create the rpm, move it to shared storage, shut down ur-tigger,
start ur-tigger2, install the rpm and still have 30-45 minutes
of test time left out of an hour.

Since the machine is somewhat underpowered, you will see
serious performance hits on your session on the real machine
while the uml machines are up.  If you really have to do this,
I *guess* (but haven't tried it) that you could nice the uml
machine - at the expense of performance there.

For both uml machines, I created startup files (I put these in
/etc/init.d for no good reason, since the uml machines are
run under my personal id, not root).  I've listed one of 
them at the bottom.  The only thing unusual is this line:

args="con1=tty:/dev/tty4

Which puts the uml (ur-tigger) console on tty4 of tigger's 
console.

I strongly suggest you don't try and do this with a COW
file.  The two machines are pretty different.  While the 
file sizes LOOK scary, they're really sparse, and quite small:

[bstrauss@tigger ur-tigger]$ ls -ls
     4 -r-xr-xr-x    1 bstrauss bstrauss     3191 May 12 18:23 control
   268 -rwxrwxr-x    1 bstrauss bstrauss   266876 Apr 28 10:04 initrd-um
     4 drwxrwxr-x    2 bstrauss bstrauss     4096 Apr 28 09:51 mnt
617580 -rwxrwxr-x    1 bstrauss bstrauss 1073741824 Jun 19 10:16 rootfs
 12252 -rwxrwxr-x    1 bstrauss bstrauss 134217728 Jun 18 17:27 swapfs
^^^^^^actual                   effective ^^^^^^^^^^

So that you can easily exchange files between the two
uml machines, follow this to setup host file access:

     http://user-mode-linux.sourceforge.net/hostfs.html

(If you're using a machine that is this tight on memory, 
running two umls simultaneously isn't advised).

===============================================
==== C r e a t i n g ==========================
===============================================

ur-tigger is used to create the rpms.

You'll need to have available all the tools you need to
compile and run ntop - via trial and error, I developed the
following list (it's in the ntop.spec file):

BuildPrereq: glibc, glibc-devel, gcc, cpp, gawk, 
             autoconf, automake, openssl, openssl-devel, 
             gdbm, gdbm-devel, libpcap, mysql, mysql-devel

Key version# information (These aren't REQUIRED, it's just
what I use):

    Kernel: 2.4.18-15um

    autoconf-2.13-14
    automake-1.4p5-2
    cpp-2.96-98
    gawk-3.1.0-3
    gcc-2.96-98
    gdbm-1.8.0-10
    gdbm-devel-1.8.0-10
    glibc-2.2.4-13
    glibc-common-2.2.4-13
    glibc-devel-2.2.4-13
    libpcap-0.6.2-9
    mysql-3.23.41-1
    mysql-devel-3.23.41-1
    openssl-0.9.6b-8
    openssl-devel-0.9.6b-8

Login to the real machine as you.

Startup the uml machine. Running the /etc/init.d/ur-tigger start
command will seize your session, so I usually connect via ssh 
from my workstation which is a separate (Windows) machine and
just leave the session up.  But I could just as easily define
two uml consoles and use them.

Login to the uml machine as root.

Under /usr/src, create the following structure (this is standard):

./redhat
./redhat/BUILD
./redhat/RPMS
./redhat/RPMS/athlon
./redhat/RPMS/i386
./redhat/RPMS/i486
./redhat/RPMS/i586
./redhat/RPMS/i686
./redhat/RPMS/noarch
./redhat/SOURCES
./redhat/SPECS
./redhat/SRPMS

Put the ntop source into ./redhat/SOURCES, along with any
other files you need:

-rw-r--r--    1 root     root          225 Jun  4 13:10 force-i386.patch
-rw-rw-r--    1 ntop     ntop      1828895 Jun  4 10:28 ntop-2.0.99-rc2.tgz
-rw-r--r--    1 root     root         3602 May 14 14:04 ntop-config.in
-rw-r--r--    1 root     root         1246 May 14 14:03 ntop.init
-rw-r--r--    1 root     root          159 Nov 23  2001 ntop.logrotate
-rw-r--r--    1 root     root         3267 Jun 18 18:12 ntop.spec

Also put the ntop.spec file into ./redhat/SPECS

The spec file is the key to the build process (This is the RC3 version,
other than directory structure and comments, it should be the 2.1 version):

Summary: ntop shows the network usage
Name: ntop
Version: 2.0.99RC3
Release:  20020704
Source: ntop-2.0.99RC3-20020704.tgz
Source1: ntop.init
Source2: ntop.logrotate
Patch1: force-i386.patch
Patch2: version.patch
Copyright: GPL
Group: Applications/System
BuildPrereq: glibc, glibc-devel, gcc, cpp, gawk, autoconf, automake, openssl,
openssl-devel, gdbm, gdbm-devel, libpcap, mysql-devel
Requires: glibc, openssl, gdbm, ncurses, libpcap
Buildroot: %{_tmppath}/%{name}-root
Prereq: /sbin/chkconfig, /sbin/ldconfig

%description
ntop is a network and traffic analyzer that provides a wealth of information
on
various networking hosts and protocols. ntop is primarily accessed via a
built-in
web interface. Optionally, data may be stored into a database for analysis or
extracted from the web server in formats suitable for manipulation in perl or
php.

Note that the command line version, intop, is largely unsupported.

See docs/1STRUN.txt for the 1st time startup procedure!

This version - RC3 - includes a fix for the https:// hangs, see
--use-sslwatchdog.

SSLv3 is enabled.
%prep
%setup -q -c ${NAME}${VERSION}
%patch 1 -P

%build
unset RPM_OPT_FLAGS
%undefine optflags
# ntop craps out here with gcc2.96-98 and full optimization!
# First, build static libraries - use the new buildAll script
cd gdchart0.94c
./buildAll.sh
cd ../ntop
# Now, configure and build ntop
%configure --enable-optimize  --bindir=%{_sbindir} --enable-sslv3
make
patch -p0 < ../../../SOURCES/version.patch
make

%install
cd ntop
mkdir -p $RPM_BUILD_ROOT/etc/rc.d/init.d \
         $RPM_BUILD_ROOT/%{_sbindir} \
         $RPM_BUILD_ROOT/etc/logrotate.d

make install DESTDIR=$RPM_BUILD_ROOT

install -c -m0755 %{SOURCE1} $RPM_BUILD_ROOT/etc/rc.d/init.d/ntop
install -c -m0644 %{SOURCE2} $RPM_BUILD_ROOT/etc/logrotate.d/ntop

%post
/sbin/chkconfig --add  ntop
/sbin/ldconfig
/sbin/service ntop condrestart > /dev/null 2>&1


%preun
if [ "$1" = "0" ]; then
        /sbin/service ntop stop > /dev/null 2>&1
        /sbin/chkconfig --del ntop
fi

%postun
if [ "$1" -ge "1" ]; then
        /sbin/service ntop condrestart > /dev/null 2>&1
fi
/sbin/ldconfig

%clean
rm -rf $RPM_BUILD_ROOT

%files
%defattr(-,root,root)
%doc ntop/AUTHORS
%doc ntop/CONTENTS
%doc ntop/MANIFESTO
%doc ntop/COPYING
%doc ntop/ChangeLog
%doc ntop/docs/FAQ
%doc ntop/docs/HACKING
%doc ntop/docs/KNOWN_BUGS
%doc ntop/docs/TODO
%doc ntop/docs/1STRUN.txt
%doc ntop/NEWS
%doc ntop/PORTING
%doc ntop/README
%doc ntop/SUPPORT_NTOP.txt
%doc ntop/THANKS
%config %{_sysconfdir}/rc.d/init.d/ntop
%config %{_sysconfdir}/logrotate.d/ntop
%{_sbindir}/ntop
%{_sbindir}/ntop-cert.pem
%{_sbindir}/intop
%{_datadir}/%{name}
%{_mandir}/man1/intop.1.gz
%{_mandir}/man8/ntop.8.gz

%{_libdir}/ntop
%{_libdir}/plugins
%{_libdir}/libntop*
%{_libdir}/libicmpPlugin*

%changelog
* Thu Jul 03 2002 Burton M. Strauss III <burton@ntopsupport.com>
- Updated to RC3

* Thu Jun 20 2002 Burton M. Strauss III <burton@ntopsupport.com>
- Updated to RC2A - unofficial post RC2 build.

* Tue Jun 04 2002 Burton M. Strauss III <burton@ntopsupport.com>
- Updated to RC2

* Fri May 17 2002 Burton M. Strauss III <burton@ntopsupport.com>
- Updated to RC1

* Mon May 13 2002 Burton M. Strauss III <burton@ntopsupport.com>
- Updated for 2.0.99 - beta - from 13May2002 snapshot

* Fri Nov 23 2001 Hal Burgiss <hal@foobox.net>
- Updated for 2.0 beta.

* Thu Oct 11 2001 Hal Burgiss <hal@foobox.net>
- Updated for 2.0 pre-release snapshots. Many changes.

It's documented in many places, it's a standard rpm file.  You can see
where I stole it from (Thanks Hal), all I did was fixup a few things.

Remember to update the key values each time:

Version: 2.0.99RC2
Release:  20020604
Source: http://luca.ntop.org/ntop-2.0.99-rc2.tgz

and the changelog.

Luca's .tgz source files don't always follow the same structure,
so you may have to change the cd commands, cd RC2/gdchart0.94c
and cd RC2/ntop (in %build and %install respectively).

The one patch forces an i386 build for maximum compatibility 
(that's also why I build for MySQL):

--- RC2/gdchart0.94c/buildAll.sh        Tue Apr 16 18:05:18 2002
+++ RC2/gdchart0.94c/buildAll.sh        Mon May 13 13:09:31 2002
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-./configure
+./configure i386-redhat-linux
 cd zlib-1.1.4/
 ./configure
 make 

(You may also have to adjust the directory structure on the
--- and +++ lines).

To actually do the build, cd to the SPECS directory and run

rpm -ba ntop.spec

When things finish, there should be a pair of .rpm files, the
binary one in ./redhat/RPMS/i386 and the source in ./redhat/SRPMS
Copy or move them to the host (real) machine.

If you have errors, it's usually missing tools or the directory
structure.  Best bet is to take the name of the failing file and
look at it (they are all standard shell scripts created by rpm
and in /var/tmp)

Shutdown the uml machine (as root, type shutdown -h now)

===============================================
==== T e s t i n g ============================
===============================================

ur-tigger2 is used to test the rpms.

You'll need to have available all the tools you need to run 
ntop - via trial and error, I developed the following list
(it's in the ntop.spec file):

Requires: glibc, openssl, gdbm, ncurses, libpcap

                                ^^^^^^^ intop only

Login to the real machine as you.

Startup the uml machine. Same warning as above about
seizing your session.

Login to the uml machine as root.

To test the rpm, all you do is uninstall the old one

rpm -e ntop

and install the new one

rpm -i ntop-xxxx.i386.rpm

Then fire up ntop (remember docs/1STRUN.txt) and let it run
as your test.

============================================================

===============================================
==== /etc/init.d/ur-tigger - startup file======
===============================================
#!/bin/sh
# $Id: RedHat-rpmbuild-HOWTO.txt 2757 2005-04-04 13:39:46Z burton $

###
###  Various settings
###
name="ur-tigger"
dirname=/home/ntop/uml/$name
mc=$name
mcp=$HOME/.uml/$name/pid
memsize="64m"
fs=" ubd0=rootfs root=/dev/ubd/0"
swap="ubd7=swapfs"
args="con1=tty:/dev/tty4"
net="eth0=tuntap,,,"
hostiface="eth0"

###
### Change to the base directory
###
cd $dirname

###
### Look for uml binary
###

PATH=.:$PATH

if [ -x $name ]
then
    linux=$name
else
    linux=linux
fi

###
### figure out host ip address
###
PATH=/sbin:/usr/sbin:$PATH
ip=`LANG="C" LC_ALL="C" ifconfig $hostiface | grep 'inet addr:' | sed 's/.*inet addr:\([0-9.]*\).*/\1/'`
net="$net$ip"

###
### look for initial ramdisk
###

initrd=""
if [ -f initrd-um ] ; then initrd="initrd=initrd-um" ; fi

###
### Process command
###
case $1 in
    start)
        shift
        exec $linux $initrd umid="$name" $fs $swap mem=$memsize $net $args "$@"
        ;;
    stop)
        uml_mconsole "$mc" halt
        exit
        ;;
    kill)
        if [ -f $mcp ]
        then
            echo "Killing pid `cat $mcp`"
            kill -9 "`cat $mcp`"
        else
            echo "Instance $name doesn't appear to be running"
        fi
        exit 
        ;;
    console|mconsole)
        exec uml_mconsole $mc
        ;;
    cad|ctrl-alt-delete)
        exec uml_mconsole $mc cad
        ;;
    reboot)
        uml_mconsole $mc reboot
        exit 
        ;;
    install)  # undocumented option used to install stuff originally
        shift
        rm -f installfs/success
        $linux rw umid="$name" $fs mem=64m ubd7=installfs $net root=/dev/ubd/7 init=/uml_stage2install.py $args "$@"
        if [ -f installfs/success ]
        then
            exitcode=0
            echo "Install succeeded"
        else
            echo "Install failed"
            exitcode=1
        fi
        rm -f installfs/opts.py 2>/dev/null # contains root password
        if [ -f installfs/initrd-um ]
        then
            cp installfs/initrd-um .
        fi
        find installfs -type d -print | xargs chmod 777 2>/dev/null
        rm -rf installfs 2>/dev/null
        exit $exitcode
        ;;
    mount)
                mount rootfs mnt/ -o loop

        exit
        ;;
    umount)
                cd ~
                umount mnt/

        exit
        ;;
    status)
        pid=`cat $mc/pid`
        echo "pid is $pid"
        ps -ef | grep $pid
        uml_mconsole $mc/mconsole version
        exit
        ;;
    df|du)
        ls -lhs
        exit
        ;;
    *)
        echo "`basename $0` (start|stop|console|reboot|status|kill|mount|umount)" 
        echo "start      starts new session"
        echo "stop       stops current session (hard halt) - safer to use"
        echo "           init 0 inside session"
        echo "reboot     reboots current session (hard reboot) - safer to use"
        echo "           init 6 inside session"
        echo "cad        sends ctrl-alt-delete"
        echo "console    starts mconsole"
        echo "status     current status"
        echo "kill       kill -9 the uml session"
        echo "mount      mounts filesystems as loopback on mnt,  you must be root"
        echo "umount     unmounts the above"
        echo "du         shows actual disk space usage"
        exit 1
esac

==========================================
Because somebody always wants to know, here is what's on the system.

Kernel: 2.4.18-15um

Installed packages (90% of which are un-necessary):

2.4.18-15um

4Suite-0.11-2
MAKEDEV-3.2-5
PyXML-0.6.5-4
SysVinit-2.78-19
a2ps-4.13b-15
alchemist-1.0.18-1
anacron-2.3-17
ash-0.3.7-2
at-3.1.8-20
authconfig-4.1.19-1
autoconf-2.13-14
automake-1.4p5-2
basesystem-7.0-2
bash-2.05-8
binutils-2.11.90.0.8-9
bzip2-1.0.1-4
bzip2-libs-1.0.1-4
chkconfig-1.2.24-1
console-tools-19990829-36
cpio-2.4.2-23
cpp-2.96-98
cracklib-2.7-12
cracklib-dicts-2.7-12
crontabs-1.10-1
cyrus-sasl-1.5.24-20
cyrus-sasl-md5-1.5.24-20
cyrus-sasl-plain-1.5.24-20
db1-1.85-7
db2-2.4.14-7
db3-3.2.9-4
dev-3.2-5
dhcpcd-1.3.18pl8-13
diffutils-2.7.2-2
dosfstools-2.7-1
e2fsprogs-1.23-2
ed-0.2-21
emacs-20.7-41
expat-1.95.1-7
file-3.35-2
filesystem-2.1.6-2
fileutils-4.1-4
findutils-4.1.7-1
freetype-2.0.3-7
gawk-3.1.0-3
gcc-2.96-98
gcc-c++-2.96-98
gdbm-1.8.0-10
gdbm-devel-1.8.0-10
glib-1.2.10-5
glibc-2.2.4-13
glibc-common-2.2.4-13
glibc-devel-2.2.4-13
gmp-3.1.1-4
grep-2.4.2-7
groff-1.17.2-3
groff-perl-1.17.2-3
grub-0.90-11
gzip-1.3-15
hdparm-4.1-2
hotplug-2001_04_24-11
indexhtml-7.2-1
info-4.0b-3
initscripts-6.40-1
ipchains-1.3.10-10
iproute-2.2.4-14
iptables-1.2.3-1
iputils-20001110-6
kbdconfig-1.9.14-1
kernel-2.4.7-10
kernel-BOOT-2.4.7-10
kernel-debug-2.4.7-10
kernel-enterprise-2.4.7-10
kernel-headers-2.4.7-10
kernel-smp-2.4.7-10
kon2-fonts-0.3.9b-7
krb5-devel-1.2.2-13
krb5-libs-1.2.2-13
krb5-workstation-1.2.2-13
ksymoops-2.4.1-1
kudzu-0.99.23-1
less-358-21
libpcap-0.6.2-9
libstdc++-2.96-98
libstdc++-devel-2.96-98
libtermcap-2.0.8-28
libxml2-2.4.2-1
libxslt-1.0.1-3
lilo-21.4.4-14
lockdev-1.0.0-14
logrotate-3.5.9-1
lokkit-0.50-6
losetup-2.11g-5
m4-1.4.1-5
mailcap-2.1.6-1
mailx-8.1.1-22
make-3.79.1-8
man-1.5i2-6
mingetty-0.9.4-18
mkbootdisk-1.4.2-3
mkinitrd-3.2.6-1
mktemp-1.5-11
modutils-2.4.6-4
mount-2.11g-5
mouseconfig-4.23-1
mpage-2.5.1-7
mysql-3.23.41-1
mysql-devel-3.23.41-1
ncurses-5.2-12
ncurses-devel-5.2-12
net-tools-1.60-3
netconfig-0.8.11-7
newt-0.50.33-1
nkf-1.92-6
ntsysv-1.2.24-1
openldap-2.0.11-13
openssh-2.9p2-7
openssh-clients-2.9p2-7
openssh-server-2.9p2-7
openssl-0.9.6b-8
openssl-devel-0.9.6b-8
openssl-perl-0.9.6b-8
pam-0.75-14
parted-1.4.16-8
passwd-0.64.1-7
patch-2.5.4-10
pcre-3.4-2
perl-5.6.0-17
perl-DBI-1.18-1
perl-DateManip-5.39-5
perl-Digest-MD5-2.13-1
perl-HTML-Parser-3.25-2
perl-HTML-Tagset-3.03-3
perl-MIME-Base64-2.12-6
perl-NKF-1.71-2
perl-Parse-Yapp-1.04-3
perl-Storable-0.6.11-6
perl-URI-1.12-5
perl-XML-Dumper-0.4-5
perl-XML-Encoding-1.01-2
perl-XML-Grove-0.46alpha-3
perl-XML-Parser-2.30-7
perl-XML-Twig-2.02-2
perl-libnet-1.0703-6
perl-libwww-perl-5.53-3
perl-libxml-enno-1.02-5
perl-libxml-perl-0.07-5
popt-1.6.4-7x
procmail-3.21-1
procps-2.0.7-11
psmisc-20.1-2
psutils-1.17-13
pwdb-0.61.1-3
python-1.5.2-35
quota-3.01pre9-3
readline-4.2-2
redhat-logos-1.1.3-1
redhat-release-7.2-1
rootfiles-7.2-1
rpm-4.0.4-7x
rpm-build-4.0.4-7x
sed-3.02-10
setserial-2.17-4
setup-2.5.7-1
setuptool-1.8-2
sh-utils-2.0.11-5
shadow-utils-20000902-4
slang-1.4.4-4
slocate-2.6-1
sysklogd-1.4.1-4
syslinux-1.52-2
tar-1.13.19-6
tcsh-6.10-6
termcap-11.0.1-10
textutils-2.0.14-2
time-1.7-14
timeconfig-3.2.2-1
tmpwatch-2.8-2
unzip-5.42-1
utempter-0.5.2-6
util-linux-2.11f-9
vim-common-5.8-7
vim-minimal-5.8-7
vixie-cron-3.0.1-63
wget-1.7-3
which-2.12-3
words-2-17
zlib-1.1.3-24



==============================================================================================
==== B u i l d m e i s t e r =================================================================
==============================================================================================

Pretty standard for RedHat.  You create a userid, buildmeister, plus the
necessary directories and use rpmbuild, just as if you were root.  The rpm
build package automatically does the translation.

The above instructions for UML are still the way to do it.  You create the
directories:

./BUILD
./RPMS
./RPMS/i386
./RPMS/noarch
./SOURCES
./SPECS
./SRPMS

in buildmeister's home instead of /usr/src.

Use the spec file in ntop's cvs - packages/RedHat/ntop.spec - and that's where
you will find the other files for SOURCES.

==============================================================================================
==== V P C ===================================================================================
==============================================================================================

Microsoft's VPC 2004 (Virtual PC) - allows you to create multiple Linuxes that
run at acceptable speed.  You use standard VPC tools to create the VM (Virtual
Machine), capture the CD-ROM for the OS you want to install and 'boot'.

The key site to reference is "What works and what doesn't" at
http://vpc.visualwin.com/.

Two cautions:

1) The standard Fedora Core 3 kernel has problems - follow the workaround in
the instructions at vpc.visualwin.com.

2) Use an external tool to capture the CD-ROM into a .iso image file.  I've
had problems with physical CDs hanging.


But basically, using VPC is just like using a real machine.  You install the
OS - typically configuring it as a minimal development machine.  Add the extra
libraries ntop requires (libpcap, gdbm, etc.) and whatever native tools you
want for package building.

Thus I usually combine VPC + Buildmeister for .rpm based systems.

Although real memory will limit the number of simultaneously running VMs, they
boot and shutdown quickly, so the boot, scp the new files, rpmbuild, test the
rpm, scp the generated file somewhere and shutdown cycle doesn't take much
longer than (and can even be shorter) than on a native machine.

Plus, for the bandwidth of downloading a few ISOs, you can have a new Linux.

As of Apr2005, I have VPCs for:

Debian, FC2, FC3, FreeBSD 4.11, FreeBSD 4.10, FreeBSD 5.3, Gentoo, RedHat 9,
RedHat 8.0, SuSE and Solaris 10.