Mount-bind directory

LXD
1

To provide some data from the host system to the container, I thought mount-bind will do the trick.
Specifically I may make a directory /data which is effectively located at:

/var/lib/lxd/storage-pools/<poolname>/containers/<containername>/rootfs/data

Now I have my container-data in:

~/container-data/<containername>/

Then I mount-bind it:

# mount --bind /home/<username>/container-data/containername /var/lib/lxd/storage-pools/<poolname>/containers/<containername>/rootfs/data

It has the desired effect that I can conveniently add any data with my user and it would directly be available inside the container.

  • the container is unprivileged - thus not even the root inside the container may write to these files then
  • the container uses directory backend (otherwise not possible?)

Now the great question - Is this a good solution?

I am a bit insecure as it probably is a “avoiding to read the docs”-move.
I think it is not a solution how the system is supposed to be used and maybe some people with more in-depth knowledge of the system could know if there are any problems to be expected.

Thank you and best regards,
Lenny

2

LXD provides this functionality as the built-in disk device type (see Instances | LXD).

Usage is like this:

lxc config device add <instance> <device name> disk source=/source/path/on/host path=/mount/path/inside/instance

This will have the same effect as above, bind mounting the source directory inside the instance, with the same UID/GID properties you saw in your own solution.

And you can also use the readonly=true and/or the shift=true properties to make the mount readonly and perform UID/GId shifting respectively.

1 Like
3

To point out the great advantages of this solution:

  • no super user access required to set it up
  • no entry in the /etc/fstab required to have it auto-mount
  • you may delete the container without manually having to unmount as super user
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4

“supposed to be solution”? Is there an issue with it, I’m a bit confused :slight_smile:

5

Nono, no problem - I thought it is very specific and correct moreso than saying “the good/better solution” which was my alternative in mind xD

Recommendation for a better label?
Ahh “this” is a more direct and neutral reference :smirk:

1 Like
6

Ah OK it was the words “supposed to be” which was implying that it wasn’t really a “solution”, but then the list of positives contradicted that :slight_smile: