Emdebian Multistrap information

Multistrap - pbuilder chroots

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The simplest way to get a build chroot is to use multistrap and pdebuild-cross which gives these advantages:

The chroot is disposable and pbuilder maintains it for you

You can mess with it without breaking the config - including logging in to the chroot:

$ sudo pbuilder login --configfile /etc/pdebuild-cross/pdebuild-cross.rc

To retain changes in the chroot for later (use with care):

$ sudo pbuilder login --configfile /etc/pdebuild-cross/pdebuild-cross.rc --save-after-login

pbuilder and pdebuild-cross retain an aptcache for you.
it takes up less space when you're not using it.

Cross-dependencies

During the development of Emdebian Crush 1.0, there was an experimental method of identifying cross-dependencies using a debian/xcontrol file which separated the Build-Depends-Tools (packages which provide tools executed during the build) and Build-Depends which provide the development headers and foreign architecture shared libraries and other architecture-dependent files.

Adding and maintaining debian/xcontrol files in packages which change their build-dependencies independently is an unwelcome burden. The current model uses xapt which also provides embuilddeps and uses the original (and maintained) debian/control file. This does mean that certain packages (those which would have been Build-Depends-Tools) are downloaded and passed to dpkg-cross, then installed as empty packages inside the chroot. This method is far simpler than the original method using apt-cross, at the cost of installing more packages. (Surprisingly, it doesn't necessarily take any more time - resolving dependencies in apt-cross was a very slow process.)

xapt and embuilddeps can also be used outside a chroot.

Note: this mechanism will change again with Multiarch.

Method

Copy one of the files from /usr/share/multistrap and tweak it. Pass that to multistrap and create a local pbuilderrc (copied from /etc/pdebuild-cross/pbuilder.rc) and give that configfile to pbuilder:

$ sudo pbuilder login --configfile mycfg

Useful packages to add

For a native build chroot - Start with /usr/share/multistrap/buildchroot-stable.conf, /usr/share/multistrap/buildchroot-testing.conf or /usr/share/multistrap/buildchroot.conf as needed.
For a cross build chroot - Start with /usr/share/multistrap/crosschroot-stable.conf, /usr/share/multistrap/crosschroot-testing.conf or /usr/share/multistrap/crosschroot.conf as needed.
For a native plain chroot - Start with /usr/share/multistrap/lenny.conf, /usr/share/multistrap/squeeze.conf or /usr/share/multistrap/sid.conf as needed.

The plain chroots may need to have a tarball name specified so that pbuilder can use them more efficiently.

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