Shell vs Command

Jetpack provides two modules for executing commands.

Command module (!command)

Executes a command directly, without a shell. Safer, but more limited.

Use when:

• You’re running a simple command without shell features.
• Security is a concern (no shell injection).
• You don’t need pipes, redirections, or shell built-ins.

- !command
  name: List files
  cmd: ls -la /tmp

- !command
  name: Run a program with arguments
  cmd: myprogram --option value

Restrictions — none of these are allowed: ; < > & * ? { } [ ] $ ` — and no pipes, redirections, or shell built-ins (like cd, export).

Shell module (!shell)

Executes a command through a real shell (default /bin/bash).

Use when:

• You need shell features (pipes, redirections).
• You’re running complex commands with shell syntax.
• You need shell built-ins or environment manipulation.

- !shell
  name: Create config file with redirection
  cmd: echo "CONFIG=value" > /etc/myapp.conf

- !shell
  name: Complex pipeline
  cmd: ps aux | grep python | awk '{print $2}' | xargs kill

- !shell
  name: Use a different shell
  cmd: echo $SHELL
  shell: /bin/zsh

Options:

• shell — which shell to use (default /bin/bash).

Both modules support templating in cmd and work in pull mode.