I’m the happy owner of a Linksys WRT54GL. OpenWRT is nice, but … well. Debian is just nicer. And I couldn’t resist the idea of running Debian on this little MIPS system. Since there’s clearly not enough space available on the Linksys, I decided to install etch in a chroot, that I would mount using NFS.

Joey tried that already, the Debian wiki provides some information, but I use another technique.

First, on another system (an i386, I debootstrap’ed a mipsel etch, using --foreign. This tells debootstrap not to run the second stage:
debootstrap --arch mipsel --foreign etch /space/debian-mipsel http://ftp.fr.debian.org/debian

Then, I modified /etc/exports to allow the router to mount that chroot:
/space/debian-mipsel 192.168.1.1(rw,sync,no_root_squash)

I mounted it on the router:
ipkg install kmod-nfs
insmod sunrpc
insmod lockd
insmod nfs
mount -t nfs star:/space/debian-mipsel /debian -o nolock
mount -t proc /dev/null /debian/proc

I set up some swap space on the NFS mount (mandatory, or debootstrap’s second stage will fail):
ipkg install losetup
ipkg install kmod-loop
ipkg install swap-utils
dd if=/dev/zero of=/debian/swapfile bs=1M count=100
losetup /dev/loop/0 /debian/swapfile
mkswap /dev/loop/0
swapon /dev/loop/0

I chrooted inside /debian, and ran debootstrap’s second stage:
chroot /debian /bin/bash
debootstrap/debootstrap --second-stage

When you are done playing, you can disable the swap space and umount everything:
swapoff /dev/loop/0
losetup -d /dev/loop/0
umount /debian/proc
sleep 1 # or umount /debian will fail
umount /debian

If you want to re-mount everything, all you need to do is:
insmod sunrpc
insmod lockd
insmod nfs
mount -t nfs star:/space/debian-mipsel /debian -o nolock
mount -t proc /dev/null /debian/proc
losetup /dev/loop/0 /debian/swapfile
swapon /dev/loop/0
chroot /debian /bin/bash

That first stage/second stage split in debootstrap is really cool: it’s an easy way to run Debian anywhere, only requiring to be able to chroot at some point.