From it's man page: "chroot - run command or interactive shell with special root directory
Remote migration from Redhat->Debian
When I got access to a better server in a server farm, I found that it came installed with RedHat9 (apparently it's hard to find a Debian CD that works with this SCSI controller), which of course could not stay. So, I followed this HOWTO:
Essentially what you do is use chroot to install Debian to your swap partition. Since it's just a base install, all that's needed is 256MB. Once that's configured, you change RH's lilo/grub configuration to use Debian (for the next boot only, so if it fails you can go back). Once you're booted into the small Debian install, format the RH9 partition, dd everything over, fsck, resize the partition, fix up a couple small things, boot into the new big Debian partition, enable swap, and done...
So now instead of a full-blown 5.6GB RH9 install, I have exactly what I want.