The RSYNC: Operation unauthorized error in Linux-based systems occurs when the remote machine or server does not have the sufficient privileges to execute the Rsync operation. In this case, the system does not allow the operation and throws an unauthorized operation error. Resolving the error can be done in several ways, depending on your specific situation and setup. Here are some potential solutions:
1. Setting Correct Permission: One of the most common reasons for this error is the necessary permissions not being provided for that specific directory or file that you are trying to access with the rsync operation. Make sure that the directories you are syncing to and from have the correct ownership and permissions. Always remember, permissions to a file or directory in Linux are defined in three sets: Read (denoted as r), Write (denoted as w), and Execute (denoted as x). Each of these sets fall into three types of users: User (file/directory owner), Group (other users in the file’s group), and Other (everyone else). To view the permissions, you can use `ls -l` command in the terminal and to change those, `chmod` or `chown` commands can be used(Auzzi, 2019).
1. Enable Rsync Daemon: If you’re running the rsync operation as a daemon on the remote host, it can lead to unauthorized errors if not properly configurated. Be sure to check if the rsync daemon is enabled in the `rsyncd.config` file, and make sure that the daemon is pointed to the correct directory path. In the `rsyncd.conf` file, include the path in a module and enable access to that particular module(Gill, 2014).
1. Avoiding Firewall Restrictions: Firewalls are designed to protect a network from threats from the external network/internet, but they can block ports necessary to complete rsync operations. Check if the firewall is blocking the rsync operation from within the network and adjust the firewall settings if necessary or switch the communication port that rsync uses.
1. Use of SSH keys: Rather than using conventional username/password authentication, setting up SSH keys for your rsync operation provides a more secure and reliable transfer mechanism. SSH keys are generated in pairs – one public, one private. The private key stays with the user (and must be kept secure), while the public key can be distributed freely and installed on any system where the user wishes to ‘log in’(Collins, 2019).
In addition to these solutions, it might be fruitful to check the RSYNC configuration file, `rsyncd.config` on the server, to see if any specific restrictions might be causing the operation unauthorized error. Remember to keep the system and its packages updated to the latest versions and to use trusted and secure systems, keys, or certificates while doing rsync operations.
Sources:
1. Anish Nath, Linux Hardening in Hostile Networks, 2017
2. Collins, S. (2019). “SSH Key Based Authentication”. Retrieved from, https://www.umsystem.edu/ums/is/infosec/remote
3. Gill, B. (2014). “Rsync (Remote Sync): 10 Practical Examples of Rsync Command in Linux”. Retrieved from, https://www.tecmint.com/rsync-local-remote-file-synchronization-commands/
4. Auzzi (2019). “How to Use chmod and chown Command in Linux”. Retrieved from, https://geekflare.com/chmod-chown-command-linux/
