zmrcd is a script that restricts the commands that can be run as the "zimbra" user via ssh.
The script exists at the following location:
This tool has no configuration options.
This script is run by ZCS tools as part of normal operations like the following:
echo "HOST:mail1.example.com status" | ssh -i ~/.ssh/zimbra_identity -o strictHostKeyChecking=no firstname.lastname@example.org "/opt/zimbra/libexec/zmrcd"