Prevent syncoid from attempting mountpoint on target

OpenZFS Sanoid
1

I use syncoid --no-privilege-elevation and occasionally I see cannot mount '/mnt/backup-tank/my-dataset': failed to create mountpoint: Permission denied in the output.

The user on the target indeed doesn’t have ZFS mount permissions. I think it shouldn’t need them because the target is a backup server and if I need anything from the backup I would only then mount it manually or just zfs send it back to the production server. Or am I missing something?

If it’s fine to not allow ZFS mount, how can I prevent syncoid from attempting to mount the dataset on the target? I think what it does is it’s looking at the source properties and tries to replicate them on the target, which includes whether it’s mounted or not, but in normal operation I only want the dataset to be mounted on the source and I don’t need it to be mounted on the target.

Thanks for reading!

2

Is the target linux or freebsd? (Not a yes or no question, I’m asking which of the two)

Last I checked, mount permissions are somehow needed in Linux at least for the initial sync. Somebody correct me if this has changed recently.

3

Both source and target are Linux (from Ubuntu to TrueNAS Scale as the backup server)

4

I found this.

Although you might think send on one end and receive on the other would be enough, full replication will require two more privileges on the receiving side: create and mount.

5

That’s a neat article, and it explains that the mount error can be avoided by setting mountpoint=none on the parent dataset on the target. But what if tha parent dataset doesn’t exist yet and is synced with syncoid -r parent-dataset ...?

Also how does this interact with --sendoptions=w? (send raw to keep an encrypted dataset encrypted during transfer and storage)
AFAIK, it’s not possible to mount the dataset without the encryption key, which is why I’m using raw-send in the first place, so that if the backup target got compromised, an attacker couldn’t read my backed up data.

6

You can try passing u to syncoid’s --recvoptions.

From man zfs-recv:

              --recvoptions=OPTIONS  Use advanced options for zfs receive (the arguments are filtered as needed), e.g.
              syncoid --recvoptions="ux recordsize o compression=lz4" sets zfs receive -u -x recordsize -o com‐
              pression=lz4 ...

and from man zfs-recv:

              --recvoptions=OPTIONS  Use advanced options for zfs receive (the arguments are filtered as needed), e.g.
              syncoid --recvoptions="ux recordsize o compression=lz4" sets zfs receive -u -x recordsize -o com‐
              pression=lz4 ...