[SOLVED] "rsync error: error in rsync protocol data stream (code 12)"

[rickNS]

Yesterday while trying to send a folder to a remote machine I get this error;

"rsync error: error in rsync protocol data stream (code 12)"

from this command, run from the "host".

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rsync -ahv ~/send/ 192.168.0.101:~/send

Researching the error here;
https://bobcares.com/blog/rsync-error-code-12/

The reasons given;
1, insufficient disk space
2, missing remote rsync
3, failure due to idle connection

None of those reasons are the case here.
Somewhere else suggested a mismatch in rsync versions, IDK if that is the case as the "host" machine is Mint 19, and the "client" is Mint 21, and rsync is a slightly different version.

The funny thing is I was able to "pull" the folder via the client from the host by reversing the command,
This worked from the client.

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rsync -ahv 192.168.0.100:~/send/ ~/send

And funnier still, I tried the same command today, from the host, and got a different error,

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ssh: connect to host 192.168.0.100 port 22: Connection refused
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: unexplained error (code 255) at io.c(235) [sender=3.1.2]

Can anyone explain, is it the different versions of rsync, (3.1.2-2 on M19, and 3.2.3-8 on M21) or something else ?

[Termy]

Given you got an SSH error, I don't think it's an rsync(1) version mismatch. Try with scp(1), if you're using SSH under the hood anyway; be interesting to see if that yields a similar naff result. Usually when I get something like that with SSH, it's because it's ill-configured, either the firewall or SSH itself.

Hang on, with that command you used, is it normal to not specify a username? Because that would be an issue with SSH, unless the server has the same username and it's available.

[rickNS]

...

Thanks Termy,
About same result with scp, "connection refused"

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scp -r ~/send2/ 192.168.0.100:~/send2
ssh: connect to host 192.168.0.100 port 22: Connection refused
lost connection

Again I was able to pull the folder using same (reversed) command from the remote machine.

1, there are no firewall activated on either (any) machine.

"is it normal to not specify a username?"

The <USERNAME>@ part is not needed if same user on both machines.

You are correct about the version of rsync NOT being the cause as I just did a send to another machine with Mint 21...no problem there.

I have occasionally noticed this kind of error in the past, but never looked into it.

[Termy]

Wracking my brains trying to remember times I've had this issue.

Just in-case there's an issue with the SSH Daemon service, run systemctl status ssh on the remote machine, then share the output. I think that would be a different error message, but I can't remember off-hand. My brain pretty much just comes back to firewall, authentication issues (IE: bad key), service stuff, and SSH configuration. I know you said you don't have the firewall enabled on any of the machines, so if you're certain of that, I'll take your word for it. Are you using keys or passwords?

[deepakdeshp]

Permissions problem?

https://www.linuxquestions.org/question ... on-922465/

[rickNS]

run systemctl status ssh on the remote machine, then share the output.

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rick@x200;~$ systemctl status ssh
Unit ssh.service could not be found

A bit strange as I "thought" I had installed all the same software on all my machines...anyway.

So I installed openssh-server
then ran systemctl start ssh.service

Are you using keys or passwords?

No passwords, but there are "keys", or "fingerprints" which sometimes change, perhaps due to updates ? (one more reason I don't like updates)

So trying to run the rsync command again I get;

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rick@t420 ~ $ rsync -ahv ~/send2/ 192.168.0.100:~/send2
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
SHA256:1LxuIHiU8J9CB2rZPHAOPCdam26Iz8ZscSSayy76BMg.
Please contact your system administrator.
Add correct host key in /home/rick/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/rick/.ssh/known_hosts:4
  remove with:
  ssh-keygen -f "/home/rick/.ssh/known_hosts" -R "192.168.0.100"
ECDSA host key for 192.168.0.100 has changed and you have requested strict checking.
Host key verification failed.
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: unexplained error (code 255) at io.c(235) [sender=3.1.2]

This error I have also seen before.
Follow the on screen directions, and now it works as should.
Will have to test after a reboot though....

Yes works after reboot
SOLVED.
Thank you very much.

[Termy]

You're welcome. You just forgot to actually install the SSH server on the remote machine. I'll be honest, I've made the same mistake before.

BTW, updates should never ever do anything to your SSH keys.