Whenever a volume produces an error, a 
notification mark will appear next to it. A message is shown on the volume's interface and on the mark tooltip:
No route to host. Check volume's IP address and port
Under the volume's JSON, the error key contains the error code. Here, the code shows 255:
{
"_id": "vol_01FWEWD03P2A13ZWQS3VAWEXAE",
"shortName": "Studio5 Motion",
"bytesRemaining": 928866540,
"bytesTotal": 955756540,
"bytesUsed": 26890000,
"enable": true,
"error": 255
}
¶ Error codes
The error codes, or exit status codes, are a convenient way to identify a problem and troubleshoot it. Below we list the possible codes and the solutions for each code.
The
0exit status code means that the process succeeded without error
¶ rsync error codes
From rsync manual page:
0 Success
1 Syntax or usage error
2 Protocol incompatibility
3 Errors selecting input/output files, dirs
4 Requested action not supported: an attempt was made to manipulate 64-bit files on a platform
that cannot support them; or an option was specified that is supported by the client and not by the server.
5 Error starting client-server protocol
6 Daemon unable to append to log-file
10 Error in socket I/O
11 Error in file I/O
12 Error in rsync protocol data stream
13 Errors with program diagnostics
14 Error in IPC code
20 Received SIGUSR1 or SIGINT
21 Some error returned by waitpid()
22 Error allocating core memory buffers
23 Partial transfer due to error
24 Partial transfer due to vanished source files
25 The --max-delete limit stopped deletions
30 Timeout in data send/receive
35 Timeout waiting for daemon connection
¶ ssh and other error codes
ssh exits with the exit status of the remote command or with 255 if an error occurred
127 Command not found (rsync installed?)
255 Connection refused or timeout
¶ Solutions
We now list the errors sorted by their code, along with some explaination and the possible ways to resolve.
¶ 12
The remote volume runs an older rsync command and has a protocol version lower than expected.
Upgrade rsync on the remote volume's host machine.
The error 12 can also occur if rsync is ran using the
rsync --rsync-pathoption and if the specified path is not found.
The error 12 can also occur along with this type of message:
deflate on token returned 0 (470 bytes left) rsync error: error in rsync protocol data stream (code 12) at token.c(476) [sender=3.2.3]This error might happen on big compressed files, like
.movof.mp4.
It is a good idea to check which version of rsync produceed this error, and update it to the latest version if it is not up-to-date. Removing the rsync option
--compressfor this link should resolve the issue. It happens if the remote host is a Synology with limited hardware. Removing the option also permits high transfer rates (x4).
¶ 14
Probably an error in the rsync command syntax.
Check the rsync options in your configuration to find a mistake in the syntax.
¶ 23
The
.SyncPlanetVolumeRoothidden file was not found in the root directory of the remote volume. The existence of this file is a switch to ensure that the volume is correctly mounted in the directory
Check if the volume is correctly mounted (after a machine reboot a mount is not automatic or sometimes fails). If it is correctly mounted, please check the permissions on the file, that is has read and write accesses.
Create this file if it is not created yet (in case of the set up of a new volume)
¶ 127
The rsync command was not found on the remote volume
Check if the rsync command is installed on the remote volume's machine and that it is accessible in your $PATH. Please install rsync if it is not installed yet.
¶ 255
The ssh client could not connect to the remote host. The connection was refused or a connection timeout occured.
Check if the volume parameters are correct (
hostname,portandusername)
Check if the remote host is correctly running ssh and listening to the correct port number
Check if the options on the remote firewall are correct.
A typical 255 error is raised when the fingerprint of the volume's host changed:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ 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:flwCLxDvuRuvZ6QxeZxzVl1q+JrCco024LhV3vpJn20. Please contact your system administrator. Add correct host key in /root/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /root/.ssh/known_hosts:1 Password authentication is disabled to avoid man-in-the-middle attacks. Keyboard-interactive authentication is disabled to avoid man-in-the-middle attacks.Remove the offending host key as suggested if the host key change was intented and understood.
¶ Older solutions
¶ 11 (Windows + Cygwin)
Error code 11 can be confusing when rsync is started as a service on a Windows platform. It can mean that the pid file for rsync already exists in the C:\Program Files\cwRsyncServer folder (or any other directory where rsync is installed) - although no other info will be given in Windows Event Log. It will become more apparent only if rsync is started as a service from the command line.
source: https://lxadm.com/index.php?title=Rsync_exit_codes&action=edit
Remove the existing pid file