Setting up a Debian/testing chroot on stable (wheezy)

2014-07-16

I run Debian/wheezy on all my computers, mainly because I can’t afford the downtime. However, once in a while, I encounter programs I need that are only in testing. For instance the new (2014-07-16) Viber linux client needs glibc-2.14 or higher, and wheezy only has 2.13. Some blog posts suggest installing libc6 from testing on your wheezy system, but I think that’s playing with fire. libc6 is crucial to many packages, and I’m not sure things will work fine if you upgrade it.

I decided to set up a Debian/testing chroot, and then install whatever I needed under it.

Setting up a testing chroot

See the Debian wiki entry on this if you don’t know what a chroot is. Here’s what I did to set it up:

• Build the chroot:

  1. Add testing or wheezy-backports to your sources.list, and then run (as root)

     [root]# aptitude install -t testing debootstrap
     [root]# mkdir -p /srv/chroot/testing
     [root]# debootstrap testing /srv/chroot/testing http://http.debian.net/debian
     

  2. Stop services in the chroot from starting:

     [root]# cat > /srv/chroot/testing/usr/sbin/policy-rc.d <<EOF
     > #!/bin/sh
     > exit 101
     > EOF
     [root]# chmod a+x /srv/chroot/testing/usr/sbin/policy-rc.d
     

• Install and configure schroot:

  1. Install schroot

     [root]# aptitude install schroot
     

  2. Edit /etc/schroot/schroot.conf and add the following sections

     [testing-desktop]
     description=Debian testing
     type=directory
     personality=linux
     preserve-environment=true
     directory=/srv/chroot/testing
     users=gautam
     profile=desktop
     
     [testing-minimal]
     description=Debian testing
     type=directory
     personality=linux
     preserve-environment=true
     directory=/srv/chroot/testing
     root-users=root
     profile=default
     aliases=default
     

     Replace gautam with your username (or a comma separated list of users).

  3. Edit /etc/schroot/desktop/fstab and uncomment the following lines:

     /var/lib/dbus   /var/lib/dbus   none    rw,bind         0       0
     /run            /run            none    rw,bind         0       0
     /run/shm        /run/shm        none    rw,bind         0       0
     

  Don’t run the testing-desktop session as root. Services started in the chroot might affect services on the host! Running testing-desktop session as a regular user should be safe.

• Make life easy in the chroot:

  1. Switch to the new chroot (testing-minimal as root)

     [root]# schroot -c testing-minimal
     

     For clarity, I’ll prefix all subsequent commands that need to be run in the chroot environment with [chroot]username>. root is root, of course, but replace gautam with your own username.

  2. Replace ischroot with /bin/true

     [root@chroot]# dpkg-divert --divert /usr/bin/ischroot.debianutils --rename /usr/bin/ischroot
     [root@chroot]# ln -s /bin/true /usr/bin/ischroot
     

  3. Install a complete desktop environment:

     [root@chroot]# aptitude install task-kde-desktop
     

     (If you just want to run viber, then you certainly don’t need the whole kde-desktop. As long as you have pulseaudio, dbus, and a few kde libraries you should be fine. But once you have your chroot setup, it’ll have many many uses so I recomend doing a full install while you’re at it. Don’t install any services (ssh/mail/etc) though.)

  4. If you’re a power shell user and want to see it in your prompt, then put the line

     ischroot && PS1=$'%{\e[36m%}[chroot]%{\e[m%}'$PS1
     

     in your zshrc. (This might work for bash users if you add a ridiculous amount of quotes.)

• Get sound working. If you’re having trouble with sound, you might have to temporarily stop pulseaudio on the host machine. Namely, try playing an audio file in the chroot:

  [gautam]$ schroot -c testing-desktop
  [gautam@chroot]$ paplay etc/beep.wav
  Connection failure: Connection refused
  pa_context_connect() failed: Connection refused
  

  If that’s the error message you see, then run this as a regular user

  [gautam]$ pulseaudio --kill
  [gautam]$ schroot -c testing-desktop
  [gautam@chroot]$ paplay etc/beep.way
  

  (Give any legal wave file to the last command of course.)

  Note, now you won’t have audio in the host system, but will in the chroot. When you’re done with your audio, either close the chroot session, or run the following

  [gautam@chroot]$ pulseaudio --kill
  [gautam]$ paplay etc/beep.way
  

• Get graphics acceleration. For this you might have to upgrade your kernel on the host, and consequently all packages with kernel modules.

  [root]# aptitude search '~i-dkms'
  i   broadcom-sta-dkms
  i   openafs-modules-dkms
  i A virtualbox-dkms
  

  I couldn’t find broadcom-sta-dkms in backports, but openafs and virtualbox were available. I upgraded those first, and then the kernel.

  [root]# aptitude -t wheezy-backports install openafs-client virtualbox
  [root]# aptitude -t wheezy-backports install linux-image-amd64 linux-headers-amd64
  

  Now reboot into the new kernel, and test graphics acceleration:

  [root]# reboot
  ...
  [gautam]$ uname -srv
  Linux 3.14-0.bpo.1-amd64 #1 SMP Debian 3.14.12-1~bpo70+1 (2014-07-13)
  
  [gautam]$ glxinfo | grep rendering
  direct rendering: Yes
  
  [gautam]$ schroot -c testing-desktop
  [gautam@chroot]$ glxinfo | grep rendering
  direct rendering: Yes
  

• Using the chroot. Of course you can run a variety of things in your new chroot. I use it very often to run python3-matplotlib (for plotting my scientific computations and numerical simulations). To get a shell run (as a regular user)

  [gautam]$ schroot -c testing-desktop
  

  following which you can run whatever you want. Alternately, you can also start a terminal:

  [gautam]$ schroot -c testing-desktop -- mrxvt
  

  (Replace mrxvt with xterm or your favourite terminal emulator.)

Installing viber.

1. Download the package from here and save it as /tmp/viber.deb

2. Install it:

   [root@chroot]# dpkg -i /tmp/viber.deb
   

   Unfortunately they haven’t put dependency info into the package. So if you’re missing a library then viber will quit silently with no error message. (I had to do a full desktop install before I could get viber to run in the chroot.)

3. Run it as a regular user. Don’t run the next command as root.

   [gautam]$ schroot -c testing-desktop -- /usr/share/viber/Viber.sh
   

BIG FAT WARNING

Be careful when deleting your chroot. All your home directories etc are mounted on the chroot. So if you decide to do rm -rf /srv/chroot/testing/ you might wind up wiping /home as well. Don’t say I didn’t warn you.

I’d suggest doing mount | grep chroot and make sure nothing funny shows up before doing any aggressive deletion.

🗫 Comments

• 

  Also works great for pipelight

  GI (2014-08-09 15:23:12)

  This also works great for pipelight which allows you to use many windows plugins in firefox. I tried it with silverlight (for Netflix), but have heard it also works for flash, widewine etc.

  To get Silverlight working, follow the instructions here in your chroot. Be sure to also enable sliverlight and change your user agent. As of 2014-08-09 Netflix works perfectly with iceweasel-30.0-2.

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