Stop if /dev is not a bind mount with loopback

[bcrochet]

At container start, /dev is snapshotted, so any new device files
don't get added unless /dev is bindmounted in. For now, check that
/dev is the same as the host's /dev via fsid. If they differ, it
means that /dev is not bindmounted.

Fixes #352

[bcrochet]

What's here now is the "quick and dirty" fix. If this is sufficient for the time being, I'd say it's good-to-go. I'm currently looking at cleaning up some of the mount code (there are lots of places that it's done now). Some deduplication is in order.

[bcrochet]

What's here now is the "quick and dirty" fix. If this is sufficient for the time being, I'd say it's good-to-go. I'm currently looking at cleaning up some of the mount code (there are lots of places that it's done now). Some deduplication is in order.

Moved around a little bit. I've added it as an additional commit. Will collapse before merging.

[cgwalters]

Thanks for working on this, our saga of filesystem mounts will probably continue for a while 😄

[bcrochet]

I got trigger-happy with pushing. I still need to address the idempotency part.

[cgwalters]

Per discussion I think simplest may be:

• Recommend -v /dev:/dev and for now error out if we're doing loopback and /dev is not the real system /dev (I think we could statx /dev versus /proc/1/root/dev and compare stx_mnt_id ?)

Other two paths are:

• The re-exec flow to force on /dev binding
• Add install alongside #380 (comment) to do dynamic remounts from host

[bcrochet]

Per discussion I think simplest may be:

• Recommend -v /dev:/dev and for now error out if we're doing loopback and /dev is not the real system /dev (I think we could statx /dev versus /proc/1/root/dev and compare stx_mnt_id ?)

Other two paths are:

• The re-exec flow to force on /dev binding
• Add install alongside #380 (comment) to do dynamic remounts from host

Agreed. Let's start with the error out and suggestion of -v /dev:/dev.

[cgwalters]

Comparing the mounts I think can be done via https://docs.rs/rustix/latest/rustix/fs/fn.statx.html

[bcrochet]

So, this code works as expected, however for some reason once -v /dev:/dev is added, the losetup is still failing for me locally. Investigating...

[bcrochet]

So, this code works as expected, however for some reason once -v /dev:/dev is added, the losetup is still failing for me locally. Investigating...

It works on a centos VM, but not on a fedora host directly. That's the only diff I have so far.