Creating sbuild chroots for Debian package testing

This is how to setup sbuild chroots for Debian packaging.

The Debian wiki explains this already pretty good.

But here is how I use and setup my chroots.

What is a chroot

From what I understood its like some kind of "VM" that uses the host Kernel, this is named a "chroot". But that's not really that is more like an environment where the OS root directory "/" is reset to some folder on you system. But for some reason I noticed they affect your host filesystem.

You can read more about it on Debian wiki fr and on Wikipedia

Setup the chroots

If you have an SSD and some useless RAM, you can use tmpfs to hold some files and avoid SSD writes: Debian wiki

Share APT cache across chroots

It takes less bandwith, you can skip this if this is not an issue for you.

This mounting technique is described on Ubuntu wiki.

mkdir /var/lib/sbuild/apt-cache
sudo chown sbuild:sbuild /var/lib/sbuild/apt-cache
# Add: /var/lib/sbuild/apt-cache  /var/cache/apt/archives  none    rw,bind 0   0
# Into: /etc/schroot/sbuild/fstab
# Run a sbuild
# Check that /var/lib/sbuild/apt-cache has new files or folders

Sid chroot

sudo sbuild-createchroot --extra-repository='deb buildd-unstable main' --extra-repository='deb buildd-sid main' --alias=sid --chroot-prefix=sid --include=eatmydata,ccache sid /srv/chroot/sid-amd64-sbuild

Update the sid chroot

sudo sbuild-shell source:sid-amd64-sbuild
apt update
apt upgrade -y

Normal chroot

sudo sbuild-createchroot --alias=bookworm --chroot-prefix=bookworm --include=eatmydata,ccache bookworm /srv/chroot/bookworm-amd64-sbuild

Experimental chroot

Create the chroot:

sudo sbuild-createchroot --chroot-prefix=experimental --extra-repository='deb experimental main' --include=eatmydata,ccache bookworm /srv/chroot/experimental-amd64-sbuild

Make sure the packages in backports are preferred above the original ones:

sudo sbuild-shell source:experimental-amd64-sbuild
echo "Package: *\nPin: release a=experimental\nPin-Priority:900" > /etc/apt/preferences.d/experimental.pref

Backports chroot

Create the chroot:

sudo sbuild-createchroot --chroot-prefix=bullseye-backports --extra-repository='deb bullseye-backports main' --include=eatmydata,ccache bullseye /srv/chroot/bullseye-backports-amd64-sbuild

Make sure the packages in backports are preferred above the original ones:

sudo sbuild-shell source:bullseye-backports-amd64-sbuild
echo "Package: *\nPin: release a=bullseye-backports\nPin-Priority:900" > /etc/apt/preferences.d/bullseye-backports.pref
# Update the chroot
apt update
apt upgrade

Early backports testing

sbuild -d bullseye-backports --extra-repository='deb buildd-bullseye-backports main'

More about this on this blog post

Ubuntu focal chroot

sudo sbuild-createchroot \
    --extra-repository='deb focal-security main restricted universe multiverse' \
    --extra-repository='deb focal-updates main restricted universe multiverse' \
    --alias=focal --chroot-prefix=focal --include=eatmydata,ccache \
    --components main,restricted,universe,multiverse \
    focal /srv/chroot/focal-amd64-sbuild

Use the chroots

cd /home/user/packages/my-package
# sid dist
sbuild -d sid
# Normal dist
sbuild -d bullseye
# Backports dist
sbuild -d bullseye-backports

List chroots

schroot -l

Remove a chroot

rm -r /srv/chroot/experimental-amd64-sbuild
# Find config the file and remove it
rm /etc/schroot/chroot.d/experimental-amd64-sbuild-F28TrU
rm /etc/sbuild/chroot/experimental-amd64-sbuild

Install a qemu chroot

This is a more like a real VM. I found some inspiration on this blog post from


apt install sbuild-qemu

Use qemu by default

In ~/.sbuildrc add this before the end

# extra parameters to pass to qemu
# --enable-kvm is not necessary, detected on the fly by autopkgtest
# ! Adjust this performance settings !
# 4096 of RAM, 2 CPUs
my @_qemu_options = ('--ram-size=4096', '--cpus=4');

# run autopkgtest inside the schroot
$run_autopkgtest = 1;
# tell sbuild to use autopkgtest as a chroot
$chroot_mode = 'autopkgtest';
# tell autopkgtest to use qemu
$autopkgtest_virt_server = 'qemu';
# tell autopkgtest-virt-qemu the path to the image
# use --debug there to show what autopkgtest is doing
$autopkgtest_virt_server_options = [ @_qemu_options, '--', '/srv/sbuild/qemu/%r-autopkgtest-%a.img' ];
# tell plain autopkgtest to use qemu, and the right image
$autopkgtest_opts = [ '--', 'qemu', @_qemu_options, '/srv/sbuild/qemu/%r-autopkgtest-%a.img'];
# no need to cleanup the chroot after build, we run in a completely clean VM
$purge_build_deps = 'never';
# no need for sudo
$autopkgtest_root_args = '';

Create a bookworm sbuild

mkdir -p /srv/sbuild/qemu/
sbuild-qemu-create --install-packages build-essential,debhelper -o /srv/sbuild/qemu/testing-autopkgtest-amd64.img testing
sudo chown root:sbuild  /srv/sbuild/qemu/testing-autopkgtest-amd64.img

Create a sid sbuild

mkdir -p /srv/sbuild/qemu/
sbuild-qemu-create --install-packages build-essential,debhelper -o /srv/sbuild/qemu/sid-autopkgtest-amd64.img sid
sudo chown root:sbuild  /srv/sbuild/qemu/sid-autopkgtest-amd64.img

Update the sid VM

sudo sbuild-qemu-update /srv/sbuild/qemu/sid-autopkgtest-amd64.img

Run commands in the VM

Forget my changes
sbuild-qemu-boot /srv/sbuild/qemu/sid-autopkgtest-amd64.img
Keep my changes
sbuild-qemu-boot --read-write /srv/sbuild/qemu/sid-autopkgtest-amd64.img