Building debian packages in a cleanroom

12 min 2264 words
Peter Tillemans Profile picture

Categories: os

Tags: debian

Overview and Goals

We build our solutions mostly on Ubuntu Natty and we deploy to Debian (currently lenny). One problem we face is that Debian has a slow release cycle and the packages are dated. Before a new release is approved and deployed to our target servers it can still take many months causing us to have to use up to 3 year old technology. So we are often faced to 'backport' packages or debianize existing packages if we want to use the current releases. In the past we had different build servers for the target architectures. However this is a heavy solution and scales poorly. It also makes upgrading to the next release that much heavier. So we need a system for building debian packages that is :

  1. Fully automated
  2. Target multiple distributions Debian (lenny,squeeze) and Ubuntu(natty, maverick)
  3. Build on development machines(a) and Jenkins/Hudson CI servers(b)
  4. easily configurable
  5. memorizable process

The goal is to make packages for internal consumption, and the process outlined here falls short of the community standards.

Enter pbuilder

Of course we are not the first or only one with this issue. In fact we are laggards and there are excellent articles on the 'net to help us with these goals. e.g.

The pbuilder program create a clean room environment of a freshly installed empty debian or ubuntu distro, chroot into it and starts building based on the project metadata, mostly from the debian/control file. It does this by unpacking a preconfigured base image of the selectable target , installing the build dependencies, building the package in the cleanroom, moving the artifacts to the hosting machine and cleaning everything up again. And it does this actually surprisingly fast. This clearly satisfies goals 1 and 2 (and half of 3 if we assume a developer has full control over his laptop). The pbuilder is configured through commandline options, which are clear and friendly enough but you end up with commandlines of several lines long which are impossible to type in a shell and are a maintenance nightmare in build scripts (clearly conflicts with point 5). Also in the ideal world we would be able to retarget a build without touching the checked out files, e.g. with environment variable (see goals 3 and 4).

Configuring pbuilder

On the Pbuilders Tricks page I found a big smart shell script to use as the pbuilder configuration file ~/.pbuilderrc.

\# Codenames for Debian suites according to their alias. Update these when needed.

\# List of Debian suites.
    "unstable" "testing" "stable" "oldstable")

\# List of Ubuntu suites. Update these when needed.
UBUNTU\_SUITES=("natty" "maverick" "jaunty" "intrepid" "hardy" "gutsy")

\# Mirrors to use. Update these to your preferred mirror.

\# Optionally use the changelog of a package to determine the suite to use if
\# none set.
if \[ -z "${DIST}" \] && \[ -r "debian/changelog" \]; then
    DIST=$(dpkg-parsechangelog | awk '/^Distribution: / {print $2}')
    # Use the unstable suite for Debian experimental packages.
    if \[ "${DIST}" == "experimental" \]; then

\# Optionally set a default distribution if none is used. Note that you can set
\# your own default (i.e. ${DIST:="unstable"}).
: ${DIST:="$(lsb\_release --short --codename)"}

\# Optionally set the architecture to the host architecture if none set. Note
\# that you can set your own default (i.e. ${ARCH:="i386"}).
: ${ARCH:="$(dpkg --print-architecture)"}

if \[ -n "${ARCH}" \]; then


\# make sure folders exist
mkdir -p $APTCACHE

echo "Target : $BUILDRESULT" >>/tmp/dist

if $(echo ${DEBIAN\_SUITES\[@\]} | grep -q $DIST); then

    OTHERMIRROR="deb file:///var/cache/pbuilder/$NAME/result ./"
    # Debian configuration
    COMPONENTS="main contrib non-free"
    DEBOOTSTRAPOPTS=("${DEBOOTSTRAPOPTS\[@\]}" "--keyring=/usr/share/keyrings/debian-archive-keyring.gpg")
    if $(echo "$STABLE\_CODENAME stable" | grep -q $DIST); then
        EXTRAPACKAGES="$EXTRAPACKAGES debian-backports-keyring"
elif $(echo ${UBUNTU\_SUITES\[@\]} | grep -q $DIST); then
    # Ubuntu configuration
    COMPONENTS="main restricted universe multiverse"
    DEBOOTSTRAPOPTS=("${DEBOOTSTRAPOPTS\[@\]}" "--keyring=/usr/share/keyrings/ubuntu-archive-keyring.gpg")
    echo "Unknown distribution: $DIST"
    exit 1

I just updated the distribution names to the current situation and added the directory where the packages are collected as a repository so subsequent builds can use these packages as dependencies. I also specified the keyrings to use for Debian and Ubuntu and made sure the expected folders are created to mount them in the clean room. I created this in my account on my development laptop and added a symbolic link in ~root/.pbuilderrc to this file so I can update it from my desktop environment and do not have to get my brain all twisted up to try to remember with which configuration I am busy in my shell, sudo, su -, … THe way the script works is that the configuration adapts itself to the content of the DIST and ARCH environment variables. So to configure lenny-amd64 as target is sufficient to do

~ > export DIST=lenny
~ > export ARCH=amd64

This approach is also perfect Jenkins or Hudson to determine the target build from checked out sources, since it can be specified in the build recipe. (satisfies goals 3b, 4 and 5) Since we have to run these programs using sudo we must make sure the environment variables are passed by sudo. We can do this in the Defaults line of the /etc/sudoers file with the envkeep instruction.

Defaults  env\_reset,env\_keep="DIST ARCH http\_proxy ftp\_proxy 
 https\_proxy no\_proxy"
... snip ...
\# Cmnd alias specification
Cmnd\_Alias PBUILDER=/usr/sbin/pbuilder, /usr/bin/pdebuild
... snip to end of file ...
\# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

\#includedir /etc/sudoers.d

You add the DIST and ARCH variables there. I also included the environment variables for proxying so I can easily switch between environment on my laptop and these changes propagate to sudo (which is also useful for plain apt-get, by the way). I also added a line to show how to make the tools available for a user without having to give their password. This is not needed for interactive work, but very much so for the user as which the CI server is running (in our case jenkins). Note that the definition should be after the group definitions, otherwise these take precedence and jenkins has to provide his password (read: is hanging during the build).

Creating the target base images

The heavy lifting is now done. Let's create an base.tgz for lenny-amd64.

~ > export DIST=lenny
~ > export ARCH=amd64
~ > sudo pbuilder create

Now go and have a cup of coffee (or read some emails). Rinse and repeat for the other target platforms.

Backporting existing packages

In theory backporting would be as simple as

~  ᐅ cd tmp
~/tmp  ᐅ apt-get source mongodb
Reading package lists... Done
Building dependency tree
Reading state information... Done
Need to get 1,316 kB of source archives.
Get:1 natty/universe mongodb 1:1.6.3-1ubuntu2 (dsc) \[2,276 B\]
Get:2 natty/universe mongodb 1:1.6.3-1ubuntu2 (tar) \[1,285 kB\]
Get:3 natty/universe mongodb 1:1.6.3-1ubuntu2 (diff) \[29.0 kB\]
Fetched 1,316 kB in 1s (679 kB/s)
gpgv: Signature made Thu 17 Mar 2011 11:49:37 PM CET using RSA key ID D5946E0F
gpgv: Can't check signature: public key not found
dpkg-source: warning: failed to verify signature on ./mongodb\_1.6.3-1ubuntu2.dsc
dpkg-source: info: extracting mongodb in mongodb-1.6.3
dpkg-source: info: unpacking mongodb\_1.6.3.orig.tar.gz
dpkg-source: info: unpacking mongodb\_1.6.3-1ubuntu2.debian.tar.gz
dpkg-source: info: applying debian-changes-1:1.6.3-1
dpkg-source: info: applying build-process-remove-rpath
dpkg-source: info: applying mozjs185
~/tmp  ᐅ DIST=lenny ARCH=amd64 sudo pbuilder build mongodb\_1.6.3-1ubuntu2.dsc
I: using fakeroot in build.
I: Current time: Thu Jul 14 14:28:17 CEST 2011
I: pbuilder-time-stamp: 1310646497
I: Building the build Environment
I: extracting base tarball \[/var/cache/pbuilder/lenny-amd64-base.tgz\]

and you should get a nice set of debian packages in */var/cache/pbuilder/lenny-amd64. In practice you will often end up with errors like :

... snip ...
The following packages have unmet dependencies:
  pbuilder-satisfydepends-dummy: Depends: xulrunner-dev (>= 2.0~) but it is not installable
The following actions will resolve these dependencies:

Remove the following packages:

Score is -9850

Writing extended state information... Done
... snip ...
I: cleaning the build env
I: removing directory /var/cache/pbuilder/build//6279 and its subdirectories

In these case you have to walk the dependency tree till you find the leafs, and walk back up the branches to the trunk. Note also that chances are that unless you target machines which only serve a very specific purpose, you might end up with packages which are uninstallable since you pull out the rug from other installed packages. However we have the principle to use 1 virtual host to deliver 1 service, hence there are very little packages deployed to them and nothing complicated like desktop environments. Simple leaf packages often build without a hitch:

~/tmp  ᐅ DIST=lenny sudo pbuilder build libevent\_1.4.13-stable-1.dsc
I: using fakeroot in build.
I: Current time: Thu Jul 14 14:44:00 CEST 2011
I: pbuilder-time-stamp: 1310647440
I: Building the build Environment
I: extracting base tarball \[/var/cache/pbuilder/lenny-amd64-base.tgz\]
I: creating local configuration
I: copying local configuration
I: mounting /proc filesystem
I: mounting /dev/pts filesystem
I: Mounting /var/cache/pbuilder/ccache
... snip ...
dpkg-genchanges: including full source code in upload
dpkg-buildpackage: full upload (original source is included)
W: no hooks of type B found -- ignoring
I: Copying back the cached apt archive contents
I: unmounting /var/cache/pbuilder/lenny-amd64/result filesystem
I: unmounting /var/cache/pbuilder/ccache filesystem
I: unmounting dev/pts filesystem
I: unmounting proc filesystem
I: cleaning the build env
I: removing directory /var/cache/pbuilder/build//15214 and its subdirectories
I: Current time: Thu Jul 14 14:49:57 CEST 2011
I: pbuilder-time-stamp: 1310647797
~/tmp  ᐅ ls -al /var/cache/pbuilder/lenny-amd64/result
total 5260
drwxr-xr-x 2 root root    4096 2011-07-13 19:47 .
drwxr-xr-x 5 root root    4096 2011-07-13 19:13 ..
-rw-r--r-- 1 pti  pti     2853 2011-07-14 14:49 libevent\_1.4.13-stable-1\_amd64.changes
-rw-r--r-- 1 pti  pti     9129 2011-07-14 14:49 libevent\_1.4.13-stable-1.diff.gz
-rw-r--r-- 1 pti  pti      907 2011-07-14 14:49 libevent\_1.4.13-stable-1.dsc
-rw-r--r-- 1 pti  pti   499603 2009-12-05 23:04 libevent\_1.4.13-stable.orig.tar.gz
-rw-r--r-- 1 pti  pti    61956 2011-07-14 14:49 libevent-1.4-2\_1.4.13-stable-1\_amd64.deb
-rw-r--r-- 1 pti  pti    31262 2011-07-14 14:49 libevent-core-1.4-2\_1.4.13-stable-1\_amd64.deb
-rw-r--r-- 1 pti  pti   172950 2011-07-14 14:49 libevent-dev\_1.4.13-stable-1\_amd64.deb
-rw-r--r-- 1 pti  pti    51588 2011-07-14 14:49 libevent-extra-1.4-2\_1.4.13-stable-1\_amd64.deb
-rw-r--r-- 1 root root    9051 2011-07-14 14:48 Packages
~/tmp  ᐅ

Using pdebuild for building packages

Many of our packages are debianized and can be build using debuild. I use here the Ubuntu sources of tokyocabinet as an example (which uses the libevent package we just built, btw):

~/tmp/tokyocabinet-1.4.37  ᐅ DIST=lenny ARCH=amd64 pdebuild
 dpkg-genchanges  >../tokyocabinet\_1.4.37-6ubuntu1\_amd64.changes
dpkg-genchanges: not including original source code in upload
dpkg-buildpackage: binary and diff upload (original source NOT included)
W: no hooks of type B found -- ignoring
I: Copying back the cached apt archive contents
I: unmounting /var/cache/pbuilder/lenny-amd64/result filesystem
I: unmounting /var/cache/pbuilder/ccache filesystem
I: unmounting dev/pts filesystem
I: unmounting proc filesystem
I: cleaning the build env
I: removing directory /var/cache/pbuilder/build//4199 and its subdirectories
I: Current time: Thu Jul 14 15:05:27 CEST 2011
I: pbuilder-time-stamp: 1310648727
~/tmp/tokyocabinet-1.4.37  ᐅ ls /var/cache/pbuilder/lenny-amd64/result

Sometimes the dependencies break on the version of debhelpers. This version is added conservatively by the dh* scripts and often is overly conservative. Many packages build just fine with older versions of the debhelpers.

Setting up automated build

To set this up on the build server we have to replicate the steps above

  1. Create the ~/.pbuilderrc file
  2. Symbolic link to this file in ~root/.pbuilderrc
  3. Allow jenkins to use sudo for building packages
  4. Create a jenkins job to (re)build the packages
  5. Create jobs to build the packages