Create a bind mount from a Proxmox host on an unprivileged lxc container

LXCBindMount.md

Proxmox Assign Bind Mount To Unprivileged Container

In order for the LXC container to have full access the proxmox host directory, a subgid is set as owner of a host directory, and an ACL is used to ensure permissions.

Bind Mount dataset to LXC

Add the following line to /etc/pve/lxc/<CT_ID>.conf

mp0:/mount/point/on/host,mp=/mount/point/on/lxc

Create group on host

In the default Proxmox configuration, unpriviliged container subgids will have the prefix "10" followed by the expected 4-digit gid.

addgroup --gid <GID (ie."101000")> <GroupName (ie."container-data")>

Set ACL for shared dataset

Any members of -GID- will have "rwx", new files from -GID- have "rwx" default Note: documentation suggests the "-d" flag should be used to assign default, however I have been able to get the desired result without, so... take that as you will

chgrp -R <GroupName> <Dataset>
chmod -R 2775 <Dataset>
setfacl -Rm g:<GID>:rwx,d:g:<GID>:rwx <Dataset>

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Inside your LXC container

Create group

GID needs to match the last 4 digits of the subgid assigned earlier

addgroup --gid <GID (ie."1000")> <GroupName (ie."container-data")>

Add users to new permitted group

usermod -aG <GroupName> <User>

You should now be able to make modifications to the assigned directory on the host system from within the unpriviliged container.

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References

https://blog.felixbrucker.com/2015/10/01/how-to-mount-host-directories-inside-a-proxmox-lxc-container/ https://www.reddit.com/r/homelab/comments/4h0erv/resolving_permissions_issues_with_host_bind/

Thank you for this. It was very helpful in getting my drive written to but, if you can offer some direction, I'm getting some errors with my CT running ZoneMinder.

I was told that maybe my group membership for root has changed because I'm getting:

root@Zoneminder:~# sudo
sudo: unable to set runas group vector: Invalid argument
sudo: /bin/bash: Invalid argument

I'm also getting this:

root@Zoneminder:/# journalctl -xeu zoneminder.service
-- The job identifier is 37174.
Jul 17 17:04:55 Zoneminder sudo[4698]: root : true : Invalid argument ; PWD=/usr/share/zoneminder/www ; USER=www-data ; COMMAND=true
Jul 17 17:04:55 Zoneminder su[4700]: (to www-data) root on none
Jul 17 17:04:55 Zoneminder su[4700]: pam_unix(su:session): session opened for user www-data(uid=33) by (uid=0)
Jul 17 17:04:55 Zoneminder su[4700]: pam_unix(su:session): session closed for user www-data
Jul 17 17:04:55 Zoneminder su[4703]: (to www-data) root on none
Jul 17 17:04:55 Zoneminder su[4703]: pam_unix(su:session): session opened for user www-data(uid=33) by (uid=0)
Jul 17 17:04:55 Zoneminder su[4703]: pam_unix(su:session): session closed for user www-data
Jul 17 17:04:55 Zoneminder systemd[1]: zoneminder.service: Control process exited, code=exited, status=1/FAILURE
-- Subject: Unit process exited
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- An ExecStart= process belonging to unit zoneminder.service has exited.
-- The process' exit code is 'exited' and its exit status is 1.
Jul 17 17:04:55 Zoneminder systemd[1]: zoneminder.service: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- The unit zoneminder.service has entered the 'failed' state with result 'exit-code'.
Jul 17 17:04:55 Zoneminder systemd[1]: Failed to start ZoneMinder CCTV recording and surveillance system.

For ZoneMinder, storage is supposed to be www-data:www-data. I'm getting:

root@Zoneminder:/mnt# ls -la
total 16
drwxr-xr-x 3 root root 3 Jul 17 14:36 .
drwxr-xr-x 17 root root 23 Jul 19 09:59 ..
drwxrwsr-x+ 4 nobody 1111 4096 Jul 17 16:04 ZoneStorage

root@Zoneminder:/mnt/ZoneStorage# ls -la
total 33
drwxrwsr-x+ 4 nobody 1111 4096 Jul 17 16:04 .
drwxr-xr-x 3 root root 3 Jul 17 14:36 ..
drwxrwsr-x+ 3 www-data 1111 4096 Jul 17 16:04 1
drwxrwsr-x+ 2 nobody 1111 16384 Jul 17 11:06 lost+found

Not sure is this offers insight:

root@Zoneminder:~# pwck
user 'lp': directory '/var/spool/lpd' does not exist
user 'news': directory '/var/spool/news' does not exist
user 'uucp': directory '/var/spool/uucp' does not exist
user 'list': directory '/var/list' does not exist
user 'irc': directory '/run/ircd' does not exist
user 'gnats': directory '/var/lib/gnats' does not exist
user 'nobody': directory '/nonexistent' does not exist
user 'messagebus': directory '/nonexistent' does not exist

I'm still learning and uid's and gid's can be overwhelming to me, but if you can offer some direction I'd highly appreciate it.

Great write up! Works like a charm. Thank you very much.

If you're using ZFS on proxmox on the bindmount and you're getting operation not supported on the setfactl command, you additionally need to:

zfs set acltype=posixacl my/dataset

Then reboot. Rebooting (or potentially re-mounting the dataset) ensures the acl type actually becomes active.

I just used the Datacenter permissions as mentioned here:
https://www.closingtags.com/writing-to-bind-mounts-from-unprivileged-lxc-containers

Very easy.