intertwingly

It turns out that the following is all it takes to install Debian Unstable in a chroot jail under Ubuntu, and then to log into that jail as root:

apt-get install debootstrap schroot
mkdir /tmp/unstable
debootstrap unstable /tmp/unstable
chroot /tmp/unstable

There are a few things that need cleaning up, however, starting with locales:

apt-get install locales
dpkg-reconfigure locales

Once there, select en_US.UTF-8 UTF-8 both to be installed, and as the default locale.

The following will eliminate a number of other warnings you may see:

echo "none /dev/pts devpts defaults 0 0" >> /etc/fstab
mount /dev/pts

Next add a user, and enable that user to log in via sudo

adduser rubys
apt-get install sudo
echo "rubys     ALL=(ALL:ALL) ALL" > /etc/sudoers.d/rubys
chmod 440 /etc/sudoers.d/rubys

Note: visudo can be used as an alternative.  For reasons I don’t understand, usermod -a -G sudo rubys did not have the desired effect.

One final bit of configuration before logging out as root: define some text that will show up in the prompt and window title area:

echo wheezy > /etc/debian_chroot

Back on your “host” operating system, add the following to /etc/schroot/schroot.conf:

[unstable]
description=Debian wheezy/sid (unstable)
directory=/tmp/unstable
root-users=rubys
aliases=wheezy,default

At this point, you should be able to “log in” to your chroot jail with the following command:

schroot