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Comment: Workaround sudo stripping environment variables causing cowbuilder --update command to fail
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sudo DIST=sid cowbuilder --update sudo HOME=$HOME DIST=sid cowbuilder --update
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  Setting HOME is necessary as sudo strips environment variables for security reasons (see [[https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=567995|Debian bug]]) - otherwise cowbuilder will not find the .pbuilderrc you have just created.

This is a tutorial for cowbuilder. See also qemubuilder.



Create the base image:

sudo cowbuilder --create

And a new and shiny build image is created in /var/cache/pbuilder/base.cow/

Every day usage

Update the base image

sudo cowbuilder --update

Build a package:

sudo cowbuilder --build somepackage.dsc


Bash and SVN tips

Setup your .bashrc according to: http://upsilon.cc/~zack/blog/posts/2007/09/svn-cowbuilder/

Building your package for many distributions at once

cowbuilder is really handy to build your pet project for many distributions at once. If you have got an amd64 system, you can easily build a package for i386 and amd64 architectures and for say stable, sid and lucid.

  • The first step involves choosing as many basepaths as you need. I chose to put them in /var/cache/pbuilder/$DIST-$ARCH/base.cow. Create the base directory, example:

    • mkdir /var/cache/pbuilder/squeeze-i386
  • Then create the base image :
    • sudo cowbuilder --create --basepath /var/cache/pbuilder/squeeze-i386/base.cow --distribution squeeze --debootstrapopts --arch --debootstrapopts i386

      Creating an ubuntu base path is trickier because one must :

      1. Obtain ubuntu signing keys
      2. Use --keyring option to specific ubuntu signing keys
      3. add universe to complete creation of chroot because the cowdancer package is in universe.

        • wget http://archive.ubuntu.com/ubuntu/project/ubuntu-archive-keyring.gpg
          sudo cp ubuntu-archive-keyring.gpg /usr/share/keyrings/
          DIST=gutsy sudo cowbuilder --create --distribution gutsy --components "main universe" --basepath /var/cache/pbuilder/gutsy-amd64.cow --mirror http://apt:9999/ubuntu --debootstrapopts --keyring=/usr/share/keyrings/ubuntu-archive-keyring.gpg
  • Create a ~/.pbuilderrc file, taking the one from Ubuntu pbuilder howto, in the Multiple pbuilders section, uncommenting the line

    • BASEPATH="/var/cache/pbuilder/$NAME/base.cow/
  • Bring your cowbuilder chroot up to date by running
    • sudo HOME=$HOME DIST=sid cowbuilder --update

    Setting HOME is necessary as sudo strips environment variables for security reasons (see Debian bug) - otherwise cowbuilder will not find the .pbuilderrc you have just created.

  • You can now build up a package. For instance a backport of nano for squeeze:
    • dget -x http://ftp.de.debian.org/debian/pool/main/n/nano/nano_2.2.6-1.dsc
      # For a Debian Squeeze on i386 target
      sudo DIST=squeeze ARCH=i386 
      # Ubuntu a Hardy on amd64 target
      sudo DIST=hardy ARCH=amd64 cowbuilder --build nano_2.2.6-1.dsc

The result will be available in: /var/cache/pbuilder/squeeze-i386/result.


  • Once everything is set up, you can use a script in a debian source package directory to build it for every distribution.

set -e

[ -d $RESULTDIR ] || mkdir $RESULTDIR

DISTLIST=$(ls -d /var/cache/pbuilder/*.cow)

for chrootdir in $DISTLIST
    sudo cowbuilder --update --basepath $chrootdir
    DIST=$(basename $chrootdir | cut -d'-' -f1)
    [ -d $RESULTDIR/$DIST ] || mkdir $RESULTDIR/$DIST
    DIST=$DIST pdebuild --pbuilder cowbuilder\
                        --buildresult $RESULTDIR/$DIST\
                        -- --basepath $chrootdir
  • You can use an apt cache to reduce the downloads on mirrors, so if the mirror is http://apt:9999/debian or http://apt:9999/ubuntu, you shoud then add --mirror http://apt:9999/debian. A good and simple proxy to use is ?approx.

  • You can use eatmydata inside the cowbuilder chroot to speed up dpkg

DIST=sid cowbuilder --login --save
apt-get install eatmydata
  • And add this /etc/pbuilderrc

if [ -z "$LD_PRELOAD" ]; then


Using with git-buildpackage

The above config can be adapted to work with the defaults of git-buildpackage:


Then the images can be created with:

DIST=sid ARCH=amd64 git-pbuilder create

And packages be built with:

DIST=sid ARCH=amd64 git-buildpackage --builder=git-pbuilder

A bug was opened to make sure the ARCH argument is coherent with the pbuilder way (ie. that it's optional), see: #646882


Slow copying and removing of the COW directory

What cowbuilder does is:

cp -al /var/cache/pbuilder/base.cow /tmp/new
rm -rf /tmp/new

Of course cowbuilder uses a different location than /tmp/new. You need to optimize those 2 commands on your computer. They should take around 0.2s each. If not, try to use the ext3 filesystem, for more details, see our benchmarks.