If I accidentally delete a command file from the Radmind server, can I recover it?

If you still have a managed client still using that exact command file, you can. Let's assume that the command file on the server was named "staff.K."

Go to the managed client computer's /var/radmind/client directory, and copy the "command.K" file from the client up to the server. There are many ways to copy it, including secure copy (scp). You can use command line or there are many GUI front-ends. Once example is the open source GUI frontend for SFTP, SCP called Fugu.

On the server, place the file in /var/radmind/command and rename it to "staff.K."

Verify the permissions of the file on the server; normally, you'd want to make sure that only root or system administrator accounts can modify it, for security purposes.