/dev not mounted inside chroot

[Egil Moeller]

The list of filesystems bind-mounted from the outside at https://git.launchpad.net/cloud-initramfs-tools/tree/overlayroot/usr/sbin/overlayroot-chroot#n72 should include /dev so that installing apt-packages that touches /users device files (null, zero, ttyX) in their postinstall scripts works, as well as just plain apt-get update.

Example failure:

gpgv: Good signature from "Ubuntu Archive Automatic Signing Key (2012) <email address hidden>"
/usr/bin/apt-key: 624: /usr/bin/apt-key: cannot create /dev/null: Permission denied

[David MacMahon (david-macmahon)]

In addition to `/dev`, I found that `/dev/pts` also needed to be mounted otherwise `apt` complained. To solve this I added both `/dev` and `/dev/pts` to the list of directories to be bind mounted. This led to another problem that `/dev` could not be unmounted first because `/dev/pts` was still bind mounted. I solved this by prepending the directories to the `mounts` variable rather than appending so that the bind mounts get unmounted in reverse order. Instead of doing:

    mounts="$mounts $lowerdir/$d"

I changed it to:

    mounts="$lowerdir/$d $mounts"

FWIW, this was on Ubuntu 22.04 (Jammy Jellyfish) with version "0.47ubuntu1" of the `overlayroot` package.