Which user do I delegate ZFS permissions to on the znapzend source?

[danboid]

I am trying to configure unprivileged (ie non-root and not using sudo) replication of snapshots to a remote pool via ssh using znapzend but the docs for this are a bit scant for my liking.

The README sez:

"[Running by an unprivileged user](https://github.com/oetiker/znapzend/#running-by-an-unprivileged-user)

In order to allow a non-privileged user to use it, the following permissions are required on the ZFS filesystems (which you can assign with zfs allow):

Sending end: destroy,hold,mount,send,snapshot,userprop

Receiving end: create,destroy,mount,receive,userprop"

The user I have to configure on the destination pool (using zfs allow) is pretty obvious, its the user given before the @ symbol in the host address of the ssh command but which user am supposed to delegate the zfs permissions to on the source machine?

Isn't the standard way to run znapzend via the systemd service? Maybe I need to edit the znapzend systemd service to specify the user I want to run znapzend as?

Giving example commands here would also be very helpful for those new to ZFS as well as those who don't use ZFS very often.

Thanks!

[danboid]

It seems a key bit of config for anyone doing ssh replication is to edit /etc/default/znapzend so it includes at least:

ZNAPZENDOPTIONS="--features=compressed --autoCreation"

Are there any other options that you think I should add?

I think both of these options should be enabled by default when using znapzendzetup. Please explain why I wouldn't want to enable/use both of these options on all of my pools or have them enabled by default?

[danboid]

It seems that I have now got znapzend working to replicate snapshots via ssh under Ubuntu 22.04.

I'm a pretty certain that it was the adding of the --autoCreation option to my /etc/default/znapzend then restarting znapzend that fixed my problems with snapshots not getting copied.

[danboid]

mbuffer doesn't seem happy so I'll disable it:

Oct 11 10:30:11 asteria znapzend[2955980]: snapshot worker for astarray/home done (3046326)
Oct 11 10:30:11 asteria znapzend[2955980]: send/receive worker for astarray/home spawned (3053685)
Oct 11 10:30:11 asteria znapzend[3053685]: starting work on backupSet astarray/home
Oct 11 10:30:12 asteria znapzend[3053685]: sending snapshots from astarray/home to [email protected]:letome/home
Oct 11 10:30:54 asteria znapzend[3053819]: cannot unmount '/home': permission denied
Oct 11 10:30:55 asteria znapzend[3053819]: mbuffer: error: outputThread: error writing to <stdout> at offset 0x100000: Broken pipe
Oct 11 10:30:55 asteria znapzend[3053819]: mbuffer: warning: error during output to <stdout>: Broken pipe
Oct 11 10:30:55 asteria znapzend[3053818]: warning: cannot send 'astarray/home@2023-10-11-103000': signal received
Oct 11 10:30:55 asteria znapzend[3053685]: ERROR: cannot send snapshots to letome/home on [email protected]
Oct 11 10:30:55 asteria znapzend[3053685]: sending snapshots from astarray/home/aaa70990 to [email protected]:letome/home/aaa70990
Oct 11 10:31:14 asteria znapzend[3053685]: sending snapshots from astarray/home/aaa71558 to [email protected]:letome/home/aaa71558
Oct 11 10:31:30 asteria znapzend[3053685]: sending snapshots from astarray/home/acs319 to [email protected]:letome/home/acs319
Oct 11 10:31:47 asteria znapzend[3053685]: sending snapshots from astarray/home/ads067 to [email protected]:letome/home/ads067
Oct 11 10:32:04 asteria znapzend[3053685]: sending snapshots from astarray/home/aee324 to [email protected]:letome/home/aee324
Oct 11 10:32:20 asteria znapzend[3053685]: sending snapshots from astarray/home/aee331 to [email protected]:letome/home/aee331
Oct 11 10:32:36 asteria znapzend[3053685]: sending snapshots from astarray/home/aee353 to [email protected]:letome/home/aee353
Oct 11 10:32:52 asteria znapzend[3053685]: sending snapshots from astarray/home/aee367 to [email protected]:letome/home/aee367

[danboid]

What is cannot unmount '/home': permission denied about? Why would znapzend need to unmount the root snapshot dir?

Maybe I need to adjust the properties of the /home dataset?

[oetiker]

hmmm that seems odd ...

[danboid]

|After I disabled the refreservation permission on the target dataset, znapzend managed to transfer 2 of the 800 datasets but thats all.

I've seen this error in syslog a couple of times now:

Oct 11 14:02:30 asteria znapzend[1438237]: send/receive for astarray/home failed: malformed JSON string, neither tag, array, object, number, string or atom, at character offset 0 (before "(end of string)") at /opt/znapzend-0.21.2/lib/Mojo/JSON.pm line 31.

[danboid]

I've tried adding Oraclemode to the features option too but its still failing.

Has anyone ever tested znapzend with 800+ datasets?

[danboid]

I think part of the answer to my question is that there is no need to delegate ZFS permissions to a user on the source znapzend machine if you are running znapzend via systemd because systemd runs as root and root can execute all zfs commands.