A chroot environment is essentially a complete self-contained Linux installation that is nested within the main system. There are several reasons one might want to do this. It can be used to try out new (or old) Ubuntu or Debian releases, for development or packaging for other releases, or for running software that’s designed for another architecture. You can even have several chroot environments on the same system if you like. The chroot environment has it’s root somewhere in your filesystem, usually under /var/chroot, with its own libraries, system binaries, etc. The chroot command is used to change the root directory to that of the chroot environment so that the rest of the system is hidden.

I am mainly interested in the last of the three usages I mentioned above. Specifically, I need to run i386 programs on my AMD 64 system when there are no native 64-bit versions available. I will outline the steps I took to create a 32-bit chroot environment on Ubuntu Feisty Fawn (7.04). I will make the root directory /var/chroot/feisty_i386, but you can name it whatever you like. These steps should also translate to previous and future releases by simply changing feisty to breezy or warty or whatever comes next (see Releases on the Ubuntu Wiki).

The following instructions assume you are root, hence the # prompt. First, you need to install debootstrap which allows you to install a basic Ubuntu (which based on Debian) system from scratch, without the need for apt or dpkg. Installing from the repository should be fine as long as the chroot environment you wish to belongs to the same release that’s running on the main system. That is, if you want a Feisty i386 chroot environment on a Feisty amd64 system, go ahead and install from the repositories:

# apt-get install debootstrap

If you want a Breezy amd64 chroot on a Feisty amd64 system, you should download an older version of the debootstrap package. See DebootstrapChroot on the Ubuntu Wiki for more details. Continue reading »