Chmod

Tool Name: files/chmod

Changes permission bits, like chmod - natively, no chmod binary.

Symlinks are never followed. The path is resolved one component at a time with openat(O_PATH|O_NOFOLLOW), each step relative to the directory the previous step opened, and the mode is changed on exactly the object that was checked. A symlink anywhere in the path - the target itself or any directory on the way - is refused. With recursive, symlinks inside the tree are skipped and listed, never followed. This keeps a privileged: true chmod from being redirected by a planted symlink (say /tmp/x -> /etc/shadow) to a file outside the user's allowed paths.

Parameter	Meaning
`path`	Absolute path (required)
`mode`	Octal (`644`, `0755`, `4755`) or symbolic (`u+x`, `go-w`, `a=r`, `+X`, `u+s`, `+t`, comma-separated) (required)
`recursive`	Also everything below a directory
`privileged`	Run as root - needed for files you don't own; authorized per path in `mcp-sudo.yaml`

Modes follow GNU chmod exactly (verified in tests across many modes), including its directory rule: a numeric mode of up to four digits keeps a directory's setuid/setgid bits - use five digits (00755) to set them exactly. X adds execute only to directories and already-executable files.

Example

Every example below shows the equivalent linuxctl command and the raw MCP JSON-RPC call it resolves to. The raw call always follows the same two-step pattern (see MCP API overview for the full explanation): open an SSE stream to get a one-time POST endpoint, then POST the JSON-RPC request there - the result streams back on the SSE connection.

linuxctl

linuxctl chmod files /tmp/demo/deploy.sh u+x

Output:

/tmp/demo/deploy.sh: 0644 (-rw-r--r--) -> 0744 (-rwxr--r--)

linuxctl (recursive - the symlink inside is skipped)

linuxctl chmod files /tmp/demo go-rwx --recursive true

Output:

/tmp/demo: 0755 (drwxr-xr-x) -> 0700 (drwx------)
/tmp/demo/deploy.sh: 0744 (-rwxr--r--) -> 0700 (-rwx------)
/tmp/demo/logs: 0755 (drwxr-xr-x) -> 0700 (drwx------)
/tmp/demo/logs/app.log: 0644 (-rw-r--r--) -> 0600 (-rw-------)
changed 4, unchanged 0, skipped 1 symlink(s) (never followed): /tmp/demo/passwd-link

linuxctl (a symlink target is refused)

linuxctl chmod files /tmp/demo/passwd-link 0600

Output:

/tmp/demo/passwd-link: refusing to follow a symbolic link

curl (raw MCP JSON-RPC)

# 1. Open the SSE stream (in the background) and capture the one-time POST endpoint
curl -N -s --cacert mcpd.crt -H "Authorization: Bearer $MCP_TOKEN" https://localhost:9091/sse &
# server sends: event: endpoint / data: /message?session_id=...

# 2. POST the tools/call request to that endpoint
curl -s --cacert mcpd.crt -X POST "https://localhost:9091/message?session_id=<from step 1>" \
  -H "Authorization: Bearer $MCP_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "id": "1", "method": "tools/call", "params": {"name": "files/chmod", "arguments": {"path": "/tmp/demo/deploy.sh", "mode": "u+x"}}}'

# 3. The result arrives on the SSE stream opened in step 1

Response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "content": [
      {
        "type": "text",
        "text": "/tmp/demo/deploy.sh: 0644 (-rw-r--r--) -> 0744 (-rwxr--r--)\n"
      }
    ]
  }
}

Example​

Example