Chroot for package testing

A reusable chroot environment can be prepared using a snapshot of a btrfs file system, a subdirectory, or a container, with sys-apps/bubblewrap.

Preparing a chroot environment

To create the snapshot, use the following command; the snapshot, subdirectory, or container, will be placed in /mnt/gentoo:

root #btrfs subvolume create /mnt/gentoo

Get the stage 3 tarball, then unpack stage 3 in it:

root #cp stage3-*.tar.xz /mnt/gentoo

root #cd /mnt/gentoo

root #tar xpvf stage3-*.tar.xz --xattrs-include='*.*' --numeric-owner

When using a btrfs file system, space and operations will be saved by creating a snapshot:

root #btrfs subvolume snapshot /mnt/gentoo /mnt/stage3

If using a container, chroot using the following:

root #bwrap --bind /mnt/gentoo / --dev /dev --proc /proc --perms 1777 --tmpfs /dev/shm --ro-bind /etc/resolv.conf /etc/resolv.conf /bin/bash --login

If not, chroot following Chrooting in the Handbook. Then set up a stable Gentoo from stage 3 by following Chrooting in the Handbook. Inside the chroot (or container), install dev-util/pkgcheck, dev-util/pkgdev, and Portage, with the gentoo-dev USE flag enabled:

root #echo "sys-apps/portage gentoo-dev" >> /etc/portage/package.use/portage

root #emerge -1av sys-apps/portage dev-util/pkgcheck dev-util/pkgdev

At this point, if using a btrfs file system, exit the chroot / container and then make a snapshot:

root # btrfs subvolume snapshot /mnt/gentoo /mnt/stable_stage3

The original subvolume may then be deleted.

Testing the package foo

If using a btrfs filesystem, create a snapshot of the stable stage 3 and chroot into it. If not, just chroot into the stable stage 3:

root #btrfs subvolume snapshot /mnt/stable_stage3 /mnt/foo

For a chroot:

root #mount --types proc /proc /mnt/foo/proc

root #mount --rbind /sys /mnt/foo/sys

root #mount --make-rslave /mnt/foo/sys

root #mount --rbind /dev /mnt/foo/dev

root #mount --make-rslave /mnt/foo/dev

root #chroot /mnt/foo /bin/bash

You can have such script in the root of your chroot directory:

FILE /mychroot/chroot.sh

mount --rbind /dev dev
mount --make-rslave dev
mount -t proc /proc proc
mount --rbind /sys sys
mount --make-rslave sys
mount --rbind /tmp tmp
mount --bind /run run

mount -o bind /var/db/repos/ var/db/repos/
mount -o bind /var/cache/distfiles/ var/cache/distfiles/

chroot . /bin/bash

For a container:

root #bwrap --bind /mnt/gentoo / --dev /dev --proc /proc --perms 1777 --tmpfs /dev/shm --ro-bind /etc/resolv.conf /etc/resolv.conf /bin/bash --login

When testing multiple packages, renaming the prompt according to the package in testing phase can prove useful:

root # export PS1="(foo) ${PS1}"

Next, create a custom repository and copy in the ebuild to be tested. Before testing the package foo/bar , emerge all its test dependencies:

root # emerge -1av --onlydeps --with-test-deps foo

Then make the adjustments of the make.conf from Package testing, and then emerge the package:

root # emerge -1av foo

Once testing is done, the btrfs file system may be deleted:

root # btrfs subvolume delete /mnt/foo

If using another file system, execute the following after each test to get back to a stable stage 3:

root # emerge --depclean

Keeping up to date

To keep a stable_stage3 up to date, it is possible to chroot into it and execute the following command:

root # emerge --sync && emerge --quiet --update --deep --newuse @world

Alternatively, set up a new stable stage 3 using the instructions from the beginning of this article.