RSync is a powerful tool that allows for the synchronization of files and directories across different locations while maintaining permissions, link, groups, and other essentials. However, sometimes error messages like “rsync: connection unexpectedly closed” or “rsync: protocol data stream (code 12) at io.c” may occur, indicating an RSYNC protocol data stream failure.
This error often signifies an issue with the communication between the local rsync client and the remote rsync daemon. There are several reasons that could be causing your RSYNC protocol data stream to fail:
1. Incorrect Syntax: Before anything else, double-check your rsync command syntax. An incorrect syntax is often the cause of a protocol data stream failure.
1. Network connectivity: If there are network issues (DNS, routing, firewall), then the connection between the client and the server may be unstable or entirely unreachable.
1. Firewall or Security Settings: Configurations in your system/network Firewall or security settings can also cause the error.
1. Server Load or Disk Space: If the server is experiencing high loads or if the disk space is insufficient, it could also cause this problem.
1. Rsync Versions: Another cause could be the rsync versions on the client and server. If they’re incompatible or one of them is outdated, it could cause issues.
To troubleshoot and resolve the error, you can take the following steps:
A. Check the Rsync command syntax you’ve used. Here is a reference for rsync command syntax from the man pages: “rsync [OPTION]… SRC [SRC]… DEST” or “rsync [OPTION]… SRC [SRC]… [USER@]HOST:DEST” etc.
B. Review server logs: If the error is coming from the server, check /var/log/messages and /var/log/secure (or equivalent logs based on your OS) for potential issues.
C. Check the network connectivity using ping, traceroute, or netstat commands.
D. Review firewall and security settings. If the protocol or port used by rsync (generally, 873) is blocked, you would need to adjust your firewall settings.
E. If server load or disk space is an issue, manage your server resources appropriately.
F. Lastly, compare the rsync versions using ‘rsync —version’ both on client and server. Upgrade if necessary. Make sure they are compatible.
These methods can help you identify and potentially rectify the rsync error.
The information in this response is compiled from different sources with authoritative knowledge about RSYNC, UNIX systems, resolving common errors etc. These include manpages(“rsync(1) – Linux man page”(n.d.)), dzone(“Common rsync errors and how to fix them”(2021)) and various threads on Unix.StackExchange, ITKnowledgeExchange and ServerFault which provide experienced, crowdsourced information on overcoming such issues. To analyze a particular situation in-depth and for complex errors, consider taking a consultation with a networking/IT professional.
