rexec

Additional Notes

rexec is a legacy command for executing commands on a remote system using the rexec protocol. It authenticates using a username and password sent over the network in cleartext, making it insecure for untrusted networks.

The rexec service listens on TCP port 512 and uses a simple authentication mechanism. Modern systems should use ssh instead, as rexec provides no encryption or strong authentication. Most distributions no longer include a rexec server by default.

Syntax

rexec [-h hostname] [-u username] [-p password] [-n] command

Parameters

• hostname: The remote host to connect to.
• username: Username for authentication on the remote host.
• password: Password for authentication.
• command: The command to execute on the remote host.

Common Options

• -a: Use automatic login via the RHOSTS environment variable or .netrc file.
• -d: Enable debug output.
• -h host: Specify the remote hostname.
• -l username: Specify the remote username.
• -n: Redirect stdin from /dev/null.
• -p password: Provide the password on the command line.
• -L localsock: Bind a local Unix socket.
• -N: Do not start a remote command, useful for port forwarding.

Examples

rexec -h remote.example.com -l alice "ls -la /tmp"

Run ls -la /tmp on the remote host as user alice.

echo "status" | rexec -h server01 -l admin

Pipe input to a command on the remote host.

Practical Notes

• rexec is obsolete. Use ssh for any new deployments.
• The rexec protocol sends passwords in cleartext over the network.
• The rexec service is defined in /etc/inetd.conf or via systemd socket activation on older distributions.
• Most modern Linux distributions do not install the rexec client or server by default.