Previously I wrote about getting Debian GNU/kFreeBSD working in a jail. I've worked on it a bit more, polishing things up so I've got it working pretty seamlessly with my existing ezjail FreeBSD jails, so everything starts automatically, and you can use the ezjail commands to stop/restart the jail.

Here are a few more notes about how things got setup for my jail I named debian:

Kernel Modules

In /boot/loader.conf, I added these lines:

fdescfs_load="YES"
linprocfs_load="YES"
linsysfs_load="YES"
tmpfs_load="YES"

Mounting Filesystems

Created /etc/fstab.debian and populated with:

linproc     /jails/debian/proc      linprocfs       rw 0 0
linsys      /jails/debian/sys       linsysfs        rw 0 0
tmpfs       /jails/debian/lib/init/rw   tmpfs       rw 0 0

ezjail Config

Created /usr/local/etc/ezjail/debian with these contents:

export jail_debian_hostname="debian"
export jail_debian_ip="127.0.0.6"
export jail_debian_interface="lo0"
export jail_debian_rootdir="/jails/debian"
export jail_debian_mount_enable="YES"
export jail_debian_devfs_enable="YES"
export jail_debian_devfs_ruleset="devfsrules_jail"
export jail_debian_fdescfs_enable="YES"
export jail_debian_exec_start="/etc/init.d/rc 3"
export jail_debian_flags="-l -u root"

I also tried adding an IPv6 address to the jail, and that seems to work OK

So you can now stop/start with jail with

service ezjail.sh stop debian
service ezjail.sh start debian

Connect to the jail console

If you create a symlink for login (so that from the jail's POV there's a /usr/bin/login, like there would be on a FreeBSD jail)

cd /jails/debian/usr/bin/
ln -s ../../bin/login .

then you can use the ezjail-admin command to get a console in the jail, with:

ezjail-admin console debian

Otherwise, I've been using my own script to get a console (which assumes bash is installed in the jail), named /usr/local/sbin/jlogin

#!/bin/sh
#
# log into a jail, running bash
#
JID=`jls | grep " $1 " | awk '{print $1}'`
exec jexec $JID env -i PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin TERM=$TERM EDITOR=$EDITOR LANG=$LANG HOME=/root bash -l

That runs as:

jlogin debian

I've been a FreeBSD user for quite some time, going back to 3.3 or so, and for the last serveral years have also been working a lot with Ubuntu Linux. So when I ran across Debian GNU/kFreeBSD, which provides a Debian environment on top of a FreeBSD kernel, I was somewhat intrigued. It got even more interesting when I found a tutorial on setting up GNU/kFreeBSD in a jail. The notion of having a Debian environment on my home FreeBSD server without having to get something like VirtualBox running was just too good to pass up.

I got it running fairly decently, but along the way ran into some small problems - and thought I'd jot down what they were and what the fixes were.

FreeBSD Update

At first, I was using FreeBSD 8.2-RELEASE, and used debootstrap to install Debian Squeeze, as the tutorial showed. Once inside the jail, things sort of worked, but most commands, aptitude especially, would die with:

User defined signal 1

It turns out you need a newer kernel than 8.2 to run kFreeBSD in a chroot, as is mentioned in the FAQ. I upgraded my FreeBSD kernel/world to 8.3-PRERELEASE (2012-02-22), and the "signal 1" problem went away.

Debian Update

The next problem was that aptitude would still die, with:

Uncaught exception: Unable to read from stdin: Operation not permitted

After reading about this bug in cwidget, it seemed an upgrade to Wheezy was needed to fix the problem - and sure enough that problem went away.

kbdcontrol and /dev/console

The upgrade to Wheezy didn't go entirely smoothly, mainly due to the kbdcontrol package (required by sysvinit) being unable to access /dev/console in the jail. I wasn't worried about keeping things in the jail isolated for security reasons, so I went ahead and added /dev/console on-the-fly to the running jail by running outside the jail:

devfs -m /jails/debian/dev rule add path 'console*' unhide
devfs -m /jails/debian/dev rule applyset

After that, the kbdcontrol package was able to be upgraded, and I seem to have a Wheezy FreeBSD jail now. Very cool.

UPDATE: A followup talks more about the actual file changes made to run as an ezjail