Model Context Protocol (MCP) for systemd

The server directly connects to systemd via its C API and so doesn't need systemctl to run.

Installation

Compile directly with

  go build systemd-mcp.go

or

  make build

Installation

A manual installation can be done with

  cp systemd-mcp /usr/local/bin/systemd-mcp
  cp ./configs/org.opensuse.systemdmcp.conf /etc/dbus-1/system.d/
  cp ./configs/org.opensuse.systemdmcp.policy /etc/polkit-1/actions/

or

  make install

Security

Interacting with systemd requires root privileges. systemd-mcp is designed with a security model based on polkit to control access to potentially dangerous operations.

Authorization Flow

1. Privilege Escalation: When you start systemd-mcp, it will check if it is running as root. If not, it will use pkexec to request administrator privileges. You will be prompted for your password to allow the application to run as root.

2. Restricted by Default: Once running as root, the daemon starts in a restricted mode. By default, it is not allowed to perform read or write operations on systemd.

3. Granting Permissions: To grant permissions, you need to run a second systemd-mcp command in another terminal.

   • To receive authorization prompts for operations, run:

     systemd-mcp --auth-register
     

     This will register a process to handle authorization requests from the main daemon. When a tool needs permissions, a polkit dialog will appear asking for your confirmation. You should keep this terminal window open.
   • On ssh sessions, you can use the --internal-agent flag which is a convenience wrapper around --auth-register and pkttyagent.

4. Pre-authorizing Permissions: You can also pre-authorize permissions when starting the daemon, or for a daemon that is already running:

   • To start the daemon with read access pre-authorized: systemd-mcp --allow-read
   • To start the daemon with write access pre-authorized: systemd-mcp --allow-write
   • To grant read access to an already running daemon: systemd-mcp --allow-read
   • To grant write access to an already running daemon: systemd-mcp --allow-write

5. Disabling Authorization: For development or in trusted environments, you can disable the polkit authorization entirely:

   systemd-mcp --noauth
   

   [!CAUTION] Using --noauth gives any client with access to systemd-mcp full control over systemd as root. Use this with extreme caution.

Command-line Options

Flag	Shorthand	Description	Default
--http		If set, use streamable HTTP at this address, instead of stdin/stdout.	""
--logfile		If set, log to this file instead of stderr.	""
--verbose	-v	Enable verbose logging.	false
--debug	-d	Enable debug logging.	false
--log-json		Output logs in JSON format (machine-readable).	false
--list-tools		List all available tools and exit.	false
--allow-write	-w	Authorize write access to systemd. Can be used when starting the daemon or to authorize a running daemon.	false
--allow-read	-r	Authorize read access to systemd. Can be used when starting the daemon or to authorize a running daemon.	false
--auth-register	-a	Register to handle authorization requests from a running daemon via polkit.	false
--internal-agent		Starts pkttyagent to handle authorization requests. A convenience wrapper around --auth-register.	false
--enabled-tools		A comma-separated list of tools to enable.	all
--timeout		Set the timeout for authentication in seconds.	5
--noauth		Disable polkit authorization and always allow read and write access.	false

Functionality

Following tools are provided:

• list_systemd_units_by_state which lists the units in the given state, also all states can be listed
• list_systemd_units_by_name which lists the units given by their pattern
• restart_reload_unit which restarts or reloads a unit
• start_unit starts a unit
• stop_unit stops a unit
• check_restart_reload check the state of reload or restart
• enable_or_disable_unit enables or disables a unit
• list_unit_files which lists the unit files known to systemd
• list_log which has access to the system log, with various filters

Testing

You can test the functions with mcptools, with e.g.

  mcptools shell go run systemd-mcp.go