|Revision 0.9.1||2002-08-14||Revised by: EH3|
|Small update for using X11 (sockets).|
|Revision 0.9||2001-12-03||Revised by: EH3|
As a developer, there is occasionally a need to code and/or
test programs on multiple Linux distributions. This mini-howto
outlines a neat chroot trick that can,
in many cases, obviate the need to reboot into different Linux
distributions to do testing or development.
In a nutshell, the "trick" is to place all the files from a
particular linux distribution into a single directory and then
chroot into that directory to
develop/test/debug your program. This approach will work provided
The kernel version of the "main" or "primary" distribution that you
are running is (at least somewhat) compatible with the "secondary" or
chroot'ed distributions, and
Your application is primarily user-space (ie. no kernel modules) and
does not depend intimately on any particular kernel features
(ie. /proc behavior).
This document is copyright 2001 by Ed Hill III. Permission is granted
to copy, distribute and/or modify this document under the terms of the
GNU Free Documentation License, Version 1.1 or any later version
published by the Free Software Foundation; with no Invariant Sections,
with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the
license is available at http://www.gnu.org/copyleft/fdl.html.
We assume that you already have:
One "main" or "primary" Linux distribution installed that is running a
2.4-series or newer kernel,
a free partition with 2--4Gigs available, and
space for the secondary installs (and any subsequent
Given those assumptions, the following outline is one way to
setup the multiple secondary Linux distributions that will be used
for development, testing, or other purposes:
First, create or locate an unused partition on one of your hard drives
that is large enough (usually 2--4Gb is sufficient) to do a basic
install of one of the secondary Linux distributions.
Install the secondary distro into this partition but do not add it to
your boot configuration. Note that this install need only include the
packages that your target application (or tests) require. For
instance, you may be able to ignore applications such as the X server
or other space-hogs.
Reboot your primary Linux distribution and mount the partition
containing the freshly-installed "secondary" distro. Copy (preferably
using tar -cp or some other method that preserves
permissions) all the files from the secondary distro to a location
such as /opt/distros/DISTRO_NAME.
Repeat steps 2--3 for any additional distributions that you wish to
install. The result should be a directory structure resembling:
where each directory contains the complete set of files resulting from
each distribution install.
With the secondary distributions installed, the steps to use
It is important to use a 2.4-series or newer Linux kernel in the
"primary" Linux distribution in order to take advantage of the
multiple mount points feature that the 2.4-series permits. For many
tasks, the /proc and /tmp
filesystems will have to be remounted in the secondary distribution
mount --bind /proc /opt/distros/redhat_6.2/proc
mount --bind /tmp /opt/distros/redhat_6.2/tmp
Also, it can be helpful to remount (rather than copy) the source tree
from the primary to the secondary distro:
mount --bind /home/USER/src/PROJECT /opt/distros/redhat_6.2/USER/src/PROJECT
Become root and use:
to obtain a shell with one of the secondary
distros. Note that the xhost command is only
necessary if you intend to use X-windows applications.
xhost +localhost chroot /opt/distros/redhat_6.2
Finally, create a user (if necessary) within the
chroot-ed shell and develop, build, and/or test
your application within this "separate" Linux distribution! Not that
you may also have to specify your DISPLAY
environment variable if you'd like to use X applications.
Done! You now have a shell that is, for all practical
purposes, running within the secondary Linux distribution of your
The ideas contained in this mini-HOWTO are not originally
mine. They are culled from posts by Ben Reed (of OpenNMS ) to one of the
lists. I found the information to be so useful that I wanted to
document the idea for others.