Using schroot to have a stable and transplantable development environment

Over the last months I’ve been working in several projects, switched laptop and reinstalled my main distribution several times. Having to replicate the development environment one time after another and reinstall the compiler, tools, editor and all sorts of dependencies that stain a desktop distribution is a major nuisance. In the worst case, things won’t work as before due to incompatibilities of the new distribution. And what about bringing new developers to a complex project with a lot of dependencies which are difficult to track? The new team member can spend days trying to replicate the development environment of the rest of the team.

Fortunately, I learnt to use a tool that solves all these problems: schroot. Now I have one chroot for each of the main projects I work on. I can “transplant” it from one distribution or computer to the next, give it to a newcoming developer so that they can start hacking in the project in minutes, or just archive it when I’m not in the project anymore. It’s true that I’m spending more disk space with this approach but, from my point of view, the advantages are worth. Moreover, working in this way you start from a “bare” distribution and if your project build system is forgetting some dependency (because it “should” be on a desktop distribution) you will notice.

Making it work on a Debian based distribution is as easy as:

sudo apt-get install schroot

After that, you have to initialize the chroot(s) to use. Each chroot can be based on their own distribution. For instance, to create one chroot based on Ubuntu Quantal 64 bit to hack on webkit (so, named after it), you have to initialize it using debootstrap:

sudo debootstrap --arch amd64 quantal /srv/chroot/webkit http://archive.ubuntu.com/ubuntu/

Then you have to configure schroot to find it by editing /etc/schroot/schroot.conf and adding the new entry. There are a several flavours to configure chroots, but my favourite one is directory-based:

[webkit]
description=Quantal for compiling Webkit
type=directory
directory=/srv/chroot/webkit
users=enrique
groups=root
root-groups=root

If you want to have an independent home dir in the chroot, comment out the corresponding line in /etc/schroot/default/fstab (and probably in desktop/fstab too). If you’re going to use WebKit2, you need to enable (uncomment) shared memory support. The resulting fstab should look like this:

/proc           /proc           none    rw,bind         0       0
/sys            /sys            none    rw,bind         0       0
/dev            /dev            none    rw,bind         0       0
/dev/pts        /dev/pts        none    rw,bind         0       0
#/home          /home           none    rw,bind         0       0
/tmp            /tmp            none    rw,bind         0       0
#/run           /run            none    rw,bind         0       0
#/run/lock      /run/lock       none    rw,bind         0       0
/dev/shm        /dev/shm        none    rw,bind         0       0
/run/shm        /run/shm        none    rw,bind         0       0

Now, to enter in the chroot:

schroot -c webkit

Schroot has an automatic session management system that allows creating, reusing and killing sessions but which can be a bit uncomfortable at the begining. If you find yourself with a lot of zombie sessions, just kill them all:

schroot -e --all-sessions

As I’ve got tired of automatic and zombie sessions, now I use a tiny webkit.sh script in $HOME/bin to create, reuse and kill them on demand. Feel free to customize it for your needs if you find it useful.

For more info, here are the original sources I used to learn about schroot:

• https://wiki.ubuntu.com/DebootstrapChroot
• https://help.ubuntu.com/community/DebootstrapChroot

UPDATE: 2014-02-03

If you want to enjoy graphics acceleration (and probably other features), the chroot needs to have the same acceleration packages than the host. In my case (Nvidia card), I needed this in the chroot to avoid a big black rectangle while running Chromium/Blink:

apt-get install nvidia-319

UPDATE: 2015-01-08

If you want to use pulseaudio in the chroot, add these paths to /etc/schroot/default/fstab (my user is “enrique”, with UID 1000, use your owns):

/var/lib/dbus /var/lib/dbus none rw,bind 0 0
/home/enrique/.config/pulse /home/enrique/.config/pulse none rw,bind 0 0
# On other distros: /home/enrique/.pulse /home/enrique/.pulse none rw,bind 0 0
/run/user/1000 /run/user/1000 none rw,bind 0 0