make bind-dirs idempotent / allow re-running bind-dirs

[adrelanos]

Qubes OS version:
R3.2

Affected VMs:
any Linux based

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bind-dirs currently has a limitations. It is not sane to re-run sudo /usr/lib/qubes/bind-dirs.sh if the system was booted with a non-empty bind-dirs configuration. (Which is by default the case in Qubes-Whonix.) That would lead to duplicate mounts.

Quote @adrelanos:

Perhaps bind-dirs should figure out the state etc.. If already mounted, avoid duplicate mount etc.

(And if it is not possible to figure out the state - keep a state file with the state.)

Quote @marmarek:

There is mountpoint tool which can check if a directory or file is a mountpoint. That would be a first step. The second one (less important here): checking if mounted thing is a file/directory from /rw/bind-dirs.

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Related source files:

• https://github.com/QubesOS/qubes-core-agent-linux/blob/master/vm-systemd/bind-dirs.sh
• https://github.com/QubesOS/qubes-core-agent-linux/blob/master/vm-systemd/mount-dirs.sh#L22
• https://github.com/QubesOS/qubes-core-agent-linux/blob/master/vm-systemd/qubes-mount-dirs.service

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Related:

• QubesOS/qubes-doc#299
• #2661

[adrelanos]

//cc @jpouellet @ypid @Rudd-O @HW42

[adrelanos]

//cc @jpouellet @ypid @Rudd-O @HW42

[HW42]

//cc [...] @HW42

Seems useful. This adds a little bit complexity which is more than outweighed by the usability improvement IMO.

Did you have more than a comment about what I think about this feature in mind when CC-ing me?

[HW42]

//cc [...] @HW42

Seems useful. This adds a little bit complexity which is more than outweighed by the usability improvement IMO.

Did you have more than a comment about what I think about this feature in mind when CC-ing me?