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chroot on Unix-like operating systems is an operation that changes the apparent root directory for the current running process and its children.(Read more ...)

Basic Installation

Building a "chroot" is very easy in Debian.

You will need:

apt-get install binutils debootstrap

mkdir -p /srv/chroot/wheezy

debootstrap --arch i386 wheezy /srv/chroot/wheezy http://http.debian.net/debian

chroot /srv/chroot/wheezy

Configuration

In general, it is necessary to create/edit key configuration points.

Create a /usr/sbin/policy-rc.d file IN THE CHROOT so that dpkg won't start daemons unless desired. This example prevents all daemons from being started in the chroot.

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

The ischroot command is buggy and does not detect that it is running in a chroot (685034). Several packages depend upon ischroot for determining correct behavior in a chroot and will operate incorrectly during upgrades if it is not fixed. The easiest way to fix it is to replace ischroot with the /bin/true command.

dpkg-divert --divert /usr/bin/ischroot.debianutils --rename /usr/bin/ischroot
ln -s /bin/true /usr/bin/ischroot

Configuring a chroot is relatively static and very specific, it may be possible to dispense with the command "top-level" and directly edit files.

/etc/passwd
/etc/groups

/etc/hosts
/etc/resolv.conf

/etc/fstab

Mounting pseudo filesystems

/proc

proc on /proc type proc (rw)
sysfs on /sys sysfs kind (rw)

/dev/pts

In this case, the primary system, run the command:

mount --bind /dev/pts /srv/chroot/wheezy/dev/pts

Default Configurations

Generally the file /etc/fstab might look like this:

# grep chroot /etc/fstab
/dev /srv/chroot/wheezy/dev auto bind 0 0
/dev/pts /srv/chroot/wheezy/dev/pts auto bind 0 0
/proc /srv/chroot/wheezy/proc auto bind 0 0

Therefore mount on the primary system would be:

# mount | grep chroot
/dev on /srv/chroot/wheezy/dev -type none (rw, bind)
/dev/pts on /srv/chroot/wheezy/dev/pts kind none (rw, bind)
/proc on /srv/chroot/wheezy/proc type none (rw, bind)

Adding / removing packages

apt-get install deborphan

deborphan -a

apt-get remove --purge telnet manpages pppconfig ipchains ...

Complementary list svgalibg1 whiptail

apt-get install emacs23 local mc

Usage

Common examples of chroot usage:

Advanced Usage

The schroot package provides a convenient wrapper for allowing unprivileged users to have access to one or more chroot environments. schroot handles the chroot(2) call as well as dropping privileges inside the chroot and bind mounting resources into the chroot (like home directories, /dev, /proc).


ToDo - Clean up from French translation.