Use libguestfs for better disk handling in the test suite

Currently we use an ad-hoc dd/@parted@ combo in the storage helper to create disk images with formatted filesystems outside of Tails to later be used within Tails (e.g. for the untrusted partitions feature). This limits us in many ways:

• the disk can only be backed by a raw image, which consumes its full capacity in disk space on the host unlike e.g. qcow2 images.
• we can only create filesystems supported by parted which are very limited in number.
• acting directly on the block device (= image) if we want to use LVM or LUKS will probably get complicated permission-wise as the test suite runs as an unprivileged user. It gets impossible if we’d use image types other than raw (unless something like qemu-nbd is used to create virtual block devices of the images, which again will require privileges).

This forces us to use udisks from inside Tails to query disk information in usb_install.feature, but this should preferably be made from the "outside" (i.e. no inside Tails, which is what we test). In the same feature we also have to completely boot Tails again in the only the expected files should persist on USB drive ... step, which is really slow, and have proved to be quite error prone when changes are made to the steps it uses (one usually only looks for step usage in .feature files, and forgets to look inside step definition files).

libguestfs supports all of the above and is part of the libvirt "family" of tools (and deal with permissions in the same, sane way), and it has ruby bindings. It seems like a perfect fit.

Feature Branch: test/7822-untrusted-partitions

Subtasks

• #8671 (closed)
• #8672 (closed)
• #8673 (closed)

Original created by @tails on 5294 (Redmine)