Schroot allows users to execute commands or interactive shells in different chroots (see schroot).

Unless otherwise stated, all commands presented on this page must be executed as root.

So, either run them as sudo <command>, or switch to root at the beginning by typing su.

Installation

apt-get install schroot

debootstrap is used to install a Debian base system(the new root), for the example below.

apt-get install debootstrap

Setup

Example

A simple example that creates a chroot and installs <some-package> for an X windows environment. This is not the safest nor a standard way of setup.

Backup:

cp /etc/schroot/schroot.conf /etc/schroot/schroot.conf.old

Create root file system:

mkdir -p /srv/chroot/test
debootstrap wheezy /srv/chroot/test

Replace the contents of /etc/schroot/schroot.conf with the following:

# schroot chroot definitions.
# See schroot.conf(5) for complete documentation of the file format.
#
# Please take note that you should not add untrusted users to
# root-groups, because they will essentially have full root access
# to your system.  They will only have root access inside the chroot,
# but that's enough to cause malicious damage.
#
# The following lines are examples only.  Uncomment and alter them to
# customise schroot for your needs, or create a new entry from scratch.
#
#
[wheezy-test]
description=Contains the SPICE program
aliases=test
type=directory
directory=/srv/chroot/test
users=jsmith
root-groups=root
profile=desktop
personality=linux
preserve-environment=true

Where jsmith is an underprivileged user.

schroot -c test

W: Failed to change to directory '/ ... is ok.

apt-get update && apt-get install <some-package>
exit

As the user jsmith execute:

xhost +
schroot -c test

From this point the <some-package> could be used...

Or,

xhost +
SESH=$(schroot -c test -b)
schroot -r -c $SESH
schroot -e -c $SESH

Troubleshooting

When you logout a schroot's session sometime it can happen that some processes keep busy the mount-point causing this error message:

~$ logout
E: 10mount: rmdir: failed to remove '/var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a': Device or resource busy
E: kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a: Chroot setup failed: stage=setup-stop

to retrive the PID you can take a piece of the name of the directory, says "d2c072e7" and look for in the /proc filesystem:

~$ grep -r d2c072e7 /proc/*/mountinfo
/proc/3919/mountinfo:195 41 253:3 / /var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a rw,relatime shared:134 - ext4 /dev/mapper/ld0-lv2 rw,stripe=256,data=ordered
/proc/3919/mountinfo:199 195 0:14 / /var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a/sys rw,nosuid,nodev,noexec,relatime shared:136 master:7 - sysfs sysfs rw
/proc/3919/mountinfo:216 195 0:3 / /var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a/proc rw,nosuid,nodev,noexec,relatime shared:151 master:12 - proc proc rw
/proc/3919/mountinfo:218 195 0:5 / /var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a/dev rw,relatime shared:153 master:2 - devtmpfs udev rw,size=10240k,nr_inodes=988768,mode=755
/proc/3919/mountinfo:223 195 0:15 / /var/lib/schroot/mount/kubuntu-d2c072e7-7e0c-4cfc-b48e-73defe8a4f0a/run rw,nosuid,relatime shared:158 master:5 - tmpfs tmpfs rw,size=1585940k,mode=755

Therefore "3919" is the PID to kill in order to remove the directory.


See Also :