pbuilder User's Manual

pbuilder stands for Personal Builder, and it is a automatic Debian Package Building system for personal environments. pbuilder aims to be an easy-to-setup system for auto-building Debian packages inside a clean-room environment, so that it is possible to verify that a package can be built on most Debian installations. The clean-room environment is achieved through the use of a chroot image, so that only minimal packages will be installed inside the chroot.

The Debian distribution consists of free software accompanied with source. The source code within Debian's "main" section must build within Debian "main", with only the explicitly specified build-dependencies installed.

The primary aim of pbuilder is different from other auto-building systems in Debian in that its aim is not to try to build as many packages as possible. It does not try to guess what a package needs, and in most cases it tries the worst choice of all if there is a choice to be made.

In this way, pbuilder tries to ensure that packages tested against pbuilder will build properly in most Debian installations, hopefully resulting in a good overall Debian source-buildability.

The goal of making Debian buildable from source is somewhat accomplished, and has seen good progress. It is known that Debian 3.0 is not quite buildable from source, but the next version should be better, and the version after.

pbuilder create will create a base chroot image. The distribution code-name needs to be specified with the --distribution command-line option. Usually, "sid" is used, and the default is now sid.

debootstrap is used to create the bare minimum Debian installation, and then build-essential packages are installed on top of the minimum installation using apt-get inside the chroot.

For fuller documentation of command-line options, see the pbuilder.8 manual page. Some configuration will be required for /etc/pbuilderrc for the mirror site ^[1] to use, and proxy configuration may be required to allow access through HTTP. See the pbuilderrc.5 manual page for details.

pbuilder update will update the chroot image. It will extract the chroot, invoke apt-get update and apt-get dist-upgrade inside the chroot, and then recreate the base tarball.

It is possible to switch the distribution which the chroot tarball is targeted at at this point. Specify --distribution sid --override-config to change the distribution to sid. ^[2]

For fuller documentation of command-line options, see the pbuilder.8 manual page

To build a package inside the chroot, invoke pbuilder build whatever.dsc. pbuilder will extract the chroot image to a temporary working directory, and satisfy the build-dependencies inside the chroot, and build the package. The built packages will be moved to a directory specified with the --buildresult command-line option.

The --basetgz option can be used to specify which chroot image to use.

pbuilder will extract a fresh chroot image created with pbuilder build and updated with pbuilder update, and populate the chroot with build-dependencies by parsing debian/control and invoking apt-get.

For fuller documentation of command-line options, see the pbuilder.8 manual page

pdebuild is a little wrapper script that does the most frequent of all tasks. A Debian Developer may try to do debuild, and build a package, inside a Debian source directory. pdebuild will allow similar control, and allow package to be built inside the chroot, to check that the current source tree will build happily inside the chroot.

pdebuild calls dpkg-source to build the source packages, and then invokes pbuilder on the resulting source package. However, unlike debuild, the resulting deb files will be found in the --buildresult directory.

See the pdebuild.1 manual page for more details.

There is a slightly different mode of operation available in pdebuild since version 0.97. pdebuild usually runs debian/rules clean outside of the chroot; however, it is possible to change the behavior to run it inside the chroot with the --use-pdebuild-internal. It will try to bind mount the working directory inside chroot, and run dpkg-buildpackage inside. It has the following characteristics, and thus cannot be made default.

It is possible to specify all settings by command-line options. However, for typing convenience, it is possible to use a configuration file.

/etc/pbuilderrc and ${HOME}/.pbuilderrc are read in when pbuilder is invoked. The possible options are documented in the pbuilderrc.5 manual page.

It is useful to use --configfile option to load up a pre-set configuration file when switching between configuration files for different distributions.

pbuilder requires full root privilege when it is satisfying the build-dependencies, but most packages do not need root privilege, or fail to build when they are root. pbuilder can create a user which is only used inside pbuilder and use that user id when building, and use the fakeroot command when root privilege is required.

BUILDUSERID configuration option should be set to a value for a user id that does not already exist on the system, so that it is more difficult for packages that are being built with pbuilder to affect the environment outside the chroot. When BUILDUSERNAME configuration option is also set, pbuilder will use the specified user name and fakeroot for building packages, instead of running as root inside chroot.

Even when using the fakerooting method, pbuilder will run with root privilege when it is required. For example, when installing packages to the chroot, pbuilder will run under root privilege.

To be able to invoke pbuilder without being root, you need to use user-mode-linux, as explained in Chapter 3, Using User-mode-linux with pbuilder.

pbuilder can be used for back-porting software from the latest Debian distribution to the older stable distribution, by using a chroot that contains an image of the older distribution, and building packages inside the chroot. There are several points to consider, and due to the following reasons, automatic back-porting is usually not possible, and manual interaction is required:

pbuilder can be automated, because its operations are non-interactive. It is possible to run pbuilder through multiple packages non-interactively. Several such scripts are known to exist. Junichi Uekawa has been running such a script since 2001, and has been filing bugs on packages that fail the test of pbuilder. There were several problems with auto-building:

But most of these problems are now getting solved. Only about 10% of Debian now fails to build from source (29 Dec 2002).

A script that was used by Junichi Uekawa is now included in the pbuilder distribution, as pbuildd.sh. It is available in /usr/share/doc/pbuilder/examples/pbuildd/ and its configuration is in /etc/pbuilder/pbuildd-config.sh. It should be easy enough to set up for people who are used to pbuilder. It has been running for quite a while, and it should be possible to set the application up on your system also. However, it is a new introduction, and please file bugs to the Debian BTS if you know of possible problems, or improved on the script considerably.

To set up pbuildd, there are some points to be aware of.

There are some people who use pbuilder to automatically back-port a subset of packages to the stable distribution.

I would like some information on how people are doing it, I would appreciate any feedback or information on how you are doing, or any examples.

pbuilder can be used for automated testing of packages. It has the feature of allowing hooks to be placed, and these hooks can try to install packages inside the chroot, or run them, or whatever else that can be done. Some known tests and ideas:

Most packages are compiled with gcc or g++ and using the default compiler version, which was gcc 2.95 for Debian GNU/Linux 3.0 (i386). However, Debian 3.0 was distributed with other compilers, under package names such as gcc-3.2 for gcc compiler version 3.2. It was therefore possible to try compiling packages against different compiler versions. pentium-builder provides an infrastructure for using a different compiler for building packages than the default gcc, by providing a wrapper script called gcc which calls the real gcc. To use pentium-builder in pbuilder, it is possible to set up the following in the configuration:

EXTRAPACKAGES="pentium-builder gcc-3.2 g++-3.2"
export DEBIAN_BUILDARCH=athlon
export DEBIAN_BUILDGCCVER=3.2
	

It will instruct pbuilder to install the pentium-builder package and also the GCC 3.2 compiler packages inside the chroot, and set the environment variables required for pentium-builder to function.

UML isn't completely trivial to set up. It would probably be useful to acquaint yourself with it a bit before attempting to use rootstrap or pbuilder-uml. For details, read /usr/share/doc/uml-utilities/README.Debian and the user-mode-linux documentation. (It's in a separate package, user-mode-linux-doc.)

user-mode-linux requires the user to be in the uml-net group in order to configure the network unless you are using slirp.

If you compile your own kernel, you may want to verify that you enable TUN/TAP support, and you might want to consider the SKAS patch.

rootstrap is a wrapper around debootstrap. It creates a Debian disk image for use with UML. To configure rootstrap, there are several requirements.

The following needs to happen:

pbuilder-user-mode-linux emulates most of pbuilder, but there are some differences.

To run pbuilder-uml in parallel on a system, there are a few things to bear in mind.

It is possible to use pbuilder-uml for other uses than just building Debian packages. pbuilder-user-mode-linux login will let a user use a shell inside the user-mode-linux pbuilder base image, and pbuilder-user-mode-linux execute will allow the user to execute a script inside the image.

You can use the script to install ssh and add a new user, so that it is possible to access inside the UML through ssh.

Note that it is not possible to use a script from /tmp due to the way pbuilder-uml mounts a tmpfs at /tmp.

The following example script may be useful in starting a sshd inside uml.

#!/bin/bash

apt-get install -y ssh xbase-clients xterm
echo "enter root password"
passwd
cp /etc/ssh/sshd_config{,-}
sed 's/X11Forwarding.*/X11Forwarding yes/' /etc/ssh/sshd_config- > /etc/ssh/sshd_config

/etc/init.d/ssh restart
ifconfig
echo "Hit enter to finish"
read
      

It often happens that pbuilder cannot create the latest chroot. Try upgrading pbuilder and debootstrap. It is currently only possible to create software that handles the past. Future prediction is a feature which may be added later after we have become comfortable with the past.

There are people who occasionally backport debootstrap to stable versions; hunt for them.

When there are errors with the debootstrap phase, the debootstrap script needs to be fixed. pbuilder does not provide a way to work around debootstrap.

Because of the way pbuilder works, there are several directories which cannot be bind-mounted when running pbuilder. The directories include /tmp, /var/cache/pbuilder, and system directories such as /etc and /usr. The recommendation is to use directories under the user's home directory for bind-mounts.

It is sometimes necessary to modify the chroot environment. login will remove the contents of the chroot after logout. It is possible to invoke a shell using hook scripts. pbuilder update executes 'E' scripts, and a sample for invoking a shell is provided as C10shell.

$ mkdir ~/loginhooks
$ cp C10shell ~/loginhooks/E10shell
$ sudo pbuilder update --hookdir ~/loginhooks/E10shell
      

It is also possible to add --save-after-exec and/or --save-after-login options to the pbuilder login session to accomplish the goal. It is possible to add the --uml-login-nocow option to pbuilder-user-mode-linux login session as well.

It is possible to set BUILDRESULTUID=$SUDO_UID in pbuilderrc to set the proper BUILDRESULTUID when using sudo.

If you are setting $TMPDIR to an unusual value, of other than /tmp, you will find that some errors may occur inside the chroot, such as dpkg-source failing.

There are two options, you may install a hook to create that directory, or set

export TMPDIR=/tmp

in pbuilderrc. Take your pick.

An example script is provided as examples/D10tmp with pbuilder.

When working with multiple chroots, it would be nice to work with scripts that reduce the amount of typing. An example script pbuilder-distribution.sh is provided as an example. Invoking the script as pbuilder-woody will invoke pbuilder with a woody chroot.

If you have some very specialized requirements on your apt setup inside pbuilder, it is possible to specify that through the --othermirror option. Try something like: --othermirror "deb http://local/mirror stable main|deb-src http://local/source/repository ./"

To use the local filesystem instead of http, it is necessary to do bind-mounting. --bindmounts is a command-line option useful for such cases.

You can use hook scripts for this. D scripts are run before satisfying build-dependency.

To make distinguishing bash prompts inside pbuilder easier, it is possible to set environment variables such as PS1 inside pbuilderrc

With versions of bash more recent than 2.05b-2-15, the value of the debian_chroot variable, if set, is included in the value of PS1 (the Bash prompt) inside the chroot. In prior versions of bash,^[3] setting PS1 in pbuilderrc worked.

example of debian_chroot

	export debian_chroot="pbuild$$"
      

example os PS1

	export PS1="pbuild chroot 32165 # "
      

For the help of low-bandwidth systems, it is possible to use /var/cache/apt/archives as the package cache. Just specify it instead of the default /var/cache/pbuilder/aptcache.

It is however not possible to do so currently with the user-mode-linux version of pbuilder, because /var/cache/apt/archives is usually only writable by root.

Use of dedicated tools such as apt-proxy is recommended, since caching of packages would benefit the system outside the scope of pbuilder.

It is known that Brian May does a backport of pbuilder, available at:

deb http://www.microcomaustralia.com.au/debian/ woody main

You might see a lot of warning messages when running pbuilder.

	dpkg-genchanges: warning: no utmp entry available and LOGNAME not defined; using uid of process (1234)
	

It is currently safe to ignore this warning message. Please report back if you find any problem with having LOGNAME unset. Setting LOGNAME caused a few problems when invoking chroot.

pbuilder does not currently allow Build-Conflicts against essential packages. It should be obvious that essential packages should not be removed from a working Debian system, and a source package should not try to force removal of such packages on people building the package.

By default, pbuilder uses hard links to manage the pbuilder package cache. It is not possible to make hard links across different devices; and thus this error will occur, depending on your set up. If this happens, set

APTCACHEHARDLINK=no

in your pbuilderrc file.

It is possible to use fakechroot instead of being root to run pbuilder; however, several things make this impractical. fakechroot overrides library loads and tries to override default libc functions when providing the functionality of virtual chroot. However, some binaries do no use libc to function, or override the overriding provided by fakechroot. One example is ldd. Inside fakechroot, ldd will check the library dependency outside of the chroot, which is not the expected behavior.

To work around the problem, fakechroot provides a patch for debootstrap. Use that, so that ldd and ldconfig are overridden.

Make sure you have set your path correctly, as described in /usr/share/doc/fakechroot/README.Debian

To use debconf inside pbuilder, setting DEBIAN_FRONTEND to “readline” in pbuilderrc should work. Setting it to “dialog” should also work, but make sure whiptail or dialog is installed inside the chroot.

If you see messages such as this when building a chroot, you are mounting the filesystem with the nodev option.

	/var/lib/dpkg/info/base-files.postinst: /dev/null: Permission denied
      

You will also have problems if you mount the filesystem with the noexec option, or nosuid. Make sure you do not have these flags set when mounting the filesystem for /var/cache/pbuilder or $BUILDPLACE.

This is not a problem when using User-mode-linux.

pbuilder is often slow. The slowest part of pbuilder is extracting the tar.gz every time pbuilder is invoked. That can be avoided by using pbuilder-user-mode-linux. pbuilder-user-mode-linux uses COW filesystem, and thus does not need to clean up and recreate the root filesystem.

pbuilder-user-mode-linux is slower in executing the actual build system, due to the usual user-mode-linux overhead for system calls. It is more friendly to the hard drive.

You may want a sign that you are inside a chroot, when working with chroot. Check out the examples/F90chrootmemo hook script. It will create a file called /CHROOT inside your chroot.

There are cases when some small experimenting is required, and you do not want to damage the main system, like when installing experimental library packages, or compiling with experimental compilers. For such cases, the pbuilder login command is available.

pbuilder login is a debugging feature for pbuilder itself, but it also allows users to have a temporary chroot.

Note that the chroot is cleaned after logging out of the shell, and mounting file systems inside it is considered harmful.

To facilitate using pbuilder for other uses, pbuilder execute is available. pbuilder execute will take a script specified in the command-line argument, and invoke the script inside the chroot.

The script can be useful for sequences of operations such as installing ssh and adding a new user inside the chroot.

LVM has a snapshot function that features Copy-on-write images. That could be used for pbuilder just as it can be used for the user-mode-linux pbuilder port. It may prove to be faster, but it is not implemented yet, and so no measurement has been made, yet.

Since user-mode-linux port seems to be more interesting, this is abandoned.

The --no-targz option of pbuilder will allow usage of pbuilder in a different way from conventional usage. It will try to use an existing chroot, and will not try to clean up after working on it. It is an operation mode more like sbuild.

It should be possible to create chroot images for dchroot with the following commands:

# pbuilder create --distribution potato --no-targz --basetgz /chroot/potato
# pbuilder create --distribution woody --no-targz --basetgz /chroot/woody
# pbuilder create --distribution sid --no-targz --basetgz /chroot/sid
	

This document was started on 28 Dec 2002 by Junichi Uekawa, trying to document what is known about pbuilder.

This documentation is available from the pbuilder source tarball, and from the CVS repository of pbuilder (web-based acces is possible). A copy of this documentation can be found on the Netfort page for pbuilder. The homepage for pbuilder is http://www.netfort.gr.jp/~dancer/software/pbuilder.html

The following is a most possibly inaccurate account of how pbuilder came to happen, and other attempts to make something like pbuilder happen. This part of the document was originally in the AUTHORS file, to give credit to those who existed before pbuilder.