Proxmox LXC mount point permissions

Add the mount point to the container

pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared

Or change the container settings

/etc/pve/lxc/1234.conf

Let’s see an example, we want to make uid 1005 accessible in an unprivileged container.

First, we have to change the container UID mapping in the file /etc/pve/lxc/1234.conf:

# uid map: from uid 0 map 1005 uids (in the ct) to the range starting 100000 (on the host), so 0..1004 (ct) → 100000..101004 (host)
lxc.idmap = u 0 100000 1005
lxc.idmap = g 0 100000 1005
# we map 1 uid starting from uid 1005 onto 1005, so 1005 → 1005
lxc.idmap = u 1005 1005 1
lxc.idmap = g 1005 1005 1
# we map the rest of 65535 from 1006 upto 101006, so 1006..65535 → 101006..165535
lxc.idmap = u 1006 101006 64530
lxc.idmap = g 1006 101006 64530

Then we have to allow lxc to actually do the mapping on the host. Since lxc creates the CT using root, we have to allow root to use these uids in the container.

First the file /etc/subuid (we allow 1 piece of uid starting from 1005):

root:1005:1

then /etc/subgid

root:1005:1

As a final step, remember to change to owner of the bind mount point directory on the host, to match the uid and gid that were made accessible to the container:

chown -R 1005:1005 /mnt/bindmounts/shared

You can start or restart the container here, it should start and see /shared mapped from the host directory /mnt/bindmounts/shared, all uids will be mapped to 65534:65534 except 1005, which would be seen (and written) as 1005:1005.

In case of problems debugging could be done by lxc-start -F -n 1234.