Development for Multiple Linux Distributions mini-HOWTO
Ed Hill
<ed@eh3.com>
2001-03-01
Revision History
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
Initial version.
This document outlines a quick hack to aid in developing and testing
user-space programs for multiple Linux distributions.
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Table of Contents
1. Introduction
1.1. Copyright and License
2. Setup
3. Using the Secondary Distributions
4. Credits
1. Introduction
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 that:
1. 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
2. Your application is primarily user-space (ie. no kernel modules) and does
not depend intimately on any particular kernel features (ie. /proc
behavior).
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1.1. Copyright and License
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] http://www.gnu.org/copyleft/fdl.html.
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2. Setup
We assume that you already have:
1. One "main" or "primary" Linux distribution installed that is running a
2.4-series or newer kernel,
2. a free partition with 2--4Gigs available, and
3. sufficient disk space for the secondary installs (and any subsequent
development/testing work).
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:
1. 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.
2. 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.
3. 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.
4. Repeat steps 2--3 for any additional distributions that you wish to
install. The result should be a directory structure resembling:
/opt/distros/redhat_6.2/
suse_7.2/
mandrake_8.1/
debian-potato/
slackware_8.0/
where each directory contains the complete set of files resulting from
each distribution install.
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3. Using the Secondary Distributions
With the secondary distributions installed, the steps to use them are:
1. 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 using:
mount --bind /proc /opt/distros/redhat_6.2/proc
mount --bind /tmp /opt/distros/redhat_6.2/tmp
2. 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
3. Become root and use:
xhost +localhost chroot /opt/distros/redhat_6.2
/bin/bash
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.
4. 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 choice.
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4. Credits
The ideas contained in this mini-HOWTO are not originally mine. They are
culled from posts by Ben Reed (of [http://www.opennms.org/] OpenNMS ) to one
of the [http://www.trilug.org/] TriLUG mailing lists. I found the information
to be so useful that I wanted to document the idea for others.
