Question

I created a username with the bash shell — a normal shell with all commands available — but I intend to use this shell for a backup service, which should allow only the rsync command. Therefore, I am trying to restrict this shell to execute rsync commands only. How can I do this with .bash_profile and .bashrc?

Additional Information: This shell is used to back up files and folders only. I connect another shell to rsync using an ssh key.

Answer 1

You can’t – not using just those files. Why not give them another shell, with fewer options?
rssh is designed for just this purpose.

Advantages of rssh over authorized_keys restrictions (not all may apply to you or be interesting):

• Can be used to control more than one user
• Restriction is applied from without rather than from within the user’s personal config – less chance of a mistake allowing them greater access
• Makes chrooting user easier
• rssh is not a general purpose shell, so even if misconfigured, the scope offered to the user is much less than if bash + authorized_keys is misconfigured.