bootstrap-vz should avoid bind-mounts from the host

[nbraud]

After encountering #292 (and before noticing a devtmpfs was still mounted), I attempted to rm -r the left-over workdir: this ended up removing the vast majority of my device files from /dev, making the host unuseable until reboot.

This exemplifies how an issue during VM build or during rollback can negatively impact the host, and should be mitigated by not mounting /dev, /dev/pts, /proc and /sys from the host (but instead creating independent instances).

[andsens]

[..] and should be mitigated by not mounting /dev, /dev/pts, /proc and /sys from the host (but instead creating independent instances).

We only mount-bind /dev.
When looking through the debootstrap code I see they do it a little differently,

in_target mount -t proc proc /proc
in_target mount -t sysfs sysfs /sys
in_target mount -t devfs devfs /dev

In bootstrap-vz, this would be:

root.add_mount('proc', 'proc', ['--types', 'proc'])
root.add_mount('sysfs', 'sys', ['--types', 'sysfs'])
root.add_mount('devfs', 'dev', ['--bind'])

(not sure about /dev/pts though).

I attempted to rm -r the left-over workdir: this ended up removing the vast majority of my device files from /dev

*ouch, sorry to hear that.

[nbraud]

@andsens I have a patchset coming that solves this.

[nbraud]

PS: Mounting procfs and sysfs this way basically use the host's.
Unfortunately, I don't have a good answer for procfs.