I have an Unraid server that until recently ran on Unraid 6.9.2. I have several userscripts that use rsync to backup files to a remote Synology over ssh. On Unraid 6.9.2. this worked perfectly. But a few days ago I upgraded to Unraid 7.0.1, and now my scripts are failing with these errors:

rsync: [sender] write error: Broken pipe (32)
rsync error: error in socket IO (code 10) at io.c(849) [sender=3.4.1]

Here is an example of a typical backup script:

rsync -avu --numeric-ids --progress --delete --log-file=/mnt/user/apps/Unraid/rsync-logs/<share>.$(date '+%Y-%m-%d_%H-%M-%S').log -e "ssh -T -p 2853 -o Compression=no -x" --relative /mnt/user/./<share> <user>@<remote ip>:/volume1/UnraidBCK\;

There isn't much concrete info to find regarding the error code, but the posts that I did find say it's happening because the rsync version on the Unraid server and the target server is not the same. I checked this, and indeed, this appears to be the case. Unraid is currenly using rsync version 3.4.1 protocol version 32. The Synology is using rsync version 3.1.2 protocol version 31. I can still manually SSH to the remote server just fine from Unraid though.

Unfortunately I never bothered to check the rsync version of Unraid 6.9.2, but I guess it has to be version 3.1.2 protocol version 31? I guess I must have been very lucky when I set up the rsync jobs in the first place that both Unraid 6.9.2 and the Synology were using the same version of rsync. Because it never occured to me this could be a thing.

It seems to be impossible to change the rsync version of the Synology, I couldn't find any information on how to do it. Is it then possible to somehow downgrade Unraid's rsync version back to version 3.1.2 protocol version 31? Or do I have to roll-back to Unraid 6.9.2?

Edited August 1, 2025Aug 1 by lococola

2 hours ago, lococola said:

There isn't much concrete info to find regarding the error code, but the posts that I did find say it's happening because the rsync version on the Unraid server and the target server is not the same

Rsync backup via script failed for me when I upgraded to Unraid 7.x.x due to the loss of support for the Nerd Tools which contained ipmitool. I was using ipmitool to power my destination Unraid server on and off via the rsync backup script. How ipmitool worked on Unraid had also changed (broken dependencies) so the old Nerd Tools version would not work standalone with Unraid. This eventually got resolved when @SimonF recompiled ipmitool for Unraid and I was back on track with rsync backups between Unraid servers.

My situation is not the same as yours as I have no Synology NAS invloved. I am sorry I cannot help with the rsync version issue; however, you would think newer versions of rsync would be backward compatible. Maybe the gap between rsync 3.4.x and 3.1.x is too big.

I'm not using ipmitool specifically but I did have Nerdtools installed on 6.9.2. I was using it for borgbackup, which I have since abandoned. Just to try I did install SimonF's Ipmitools, but as expected it did not solve the issue for me.

Thanks for replying though, perhaps the removal of Nerdtools is in some other way responsible for the issues that I'm having now. Something to investigate. Though, looking at my scripts, I can't imagine any such dependency for my scripts.

If anyone has any experience with version conflicts regarding rsync I'd love to hear them.

Well, looks like I got a little further with this. I found some info on a Github thread discussing issues with rsync when using quotes in the remote path. I do use quotes in my script but not to cordon offremote paths specifically. Anyway, it was suggested to add --old-args to the command, so I thought why not try. And guess what, this solved my issue. The backup jobs are running again.

I'm not totally certain this doesn't come with some caveats. I read something about file permissions being lost, but I have done a little testing and I did not see these issues. I'm going to do more extensive restore tests this weekend.

So it does appear newer versions of rsync work somewhat differently than older versions, including how it handles quotes in rsync commands. And I'm frankly surprised no information at all is to be found on this forum. Surely I'm not the only one using rsync to backup to remote servers that may use old versions of rsync. Very strange.

Edited August 1, 2025Aug 1 by lococola