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Packaging Guide

5. Using Chroots

If you are running one version of Ubuntu but working on packages for another versions you can create the environment of the other version with a chroot.

A chroot allows you to have a full filesystem from another distribution which you can work in quite normally. It avoids the overhead of running a full virtual machine.

5.1. Creating a Chroot

Use the command debootstrap to create a new chroot:

$ sudo debootstrap trusty trusty/

This will create a directory trusty and install a minimal trusty system into it.

If your version of debootstrap does not know about Trusty you can try upgrading to the version in backports.

You can then work inside the chroot:

$ sudo chroot trusty

Where you can install or remove any package you wish without affecting your main system.

You might want to copy your GPG/ssh keys and Bazaar configuration into the chroot so you can access and sign packages directly:

$ sudo mkdir trusty/home/<username>
$ sudo cp -r ~/.gnupg ~/.ssh ~/.bazaar trusty/home/<username>

To stop apt and other programs complaining about missing locales you can install your relevant language pack:

$ apt-get install language-pack-en

If you want to run X programs you will need to bind the /tmp directory into the chroot, from outside the chroot run:

$ sudo mount -t none -o bind /tmp trusty/tmp
$ xhost +

Some programs may need you to bind /dev or /proc.

For more information on chroots see our Debootstrap Chroot wiki page.

5.2. Alternatives

SBuild is a system similar to PBuilder for creating an environment to run test package builds in. It closer matches that used by Launchpad for building packages but takes some more setup compared to PBuilder. See the Security Team Build Environment wiki page for a full explanation.

Full virtual machines can be useful for packaging and testing programs. TestDrive is a program to automate syncing and running daily ISO images, see the TestDrive wiki page for more information.

You can also set up pbuilder to pause when it comes across a build failure. Copy C10shell from /usr/share/doc/pbuilder/examples into a directory and use the --hookdir= argument to point to it.

Amazon’s EC2 cloud computers allow you to hire a computer paying a few US cents per hour, you can set up Ubuntu machines of any supported version and package on those. This is useful when you want to compile many packages at the same time or to overcome bandwidth restraints.