[App] run system commands

Introduction

Via any of enabled laitos daemons, you may run operating system (shell) commands. This works on all OS platforms supported by laitos.

Configuration

This app is always enabled for use in the default configuration, which restricts command execution to these programs without additional parameters:

• arch arp blkid cal date df dmesg dnsdomainname false free
• groups hostid hostname id ifconfig ipconfig iostat ipcs
• kbd_mode ls lsof lspci lsusb mpstat netstat nproc
• ps pstree pwd route stty tty uname uptime whoami

To customise configuration, under JSON object Features, construct a JSON object called Shell that has the following mandatory properties:

Property	Type	Meaning	Default value
InterpreterPath	string	Absolute path to the system shell interpreter, such as /bin/bash.	Automatically detected, e.g. bash, powershell.
Unrestricted	true/false	When true, allow executing arbitrary commands incl. CLI parameters.	False - only allow executing predefined & hard-coded commands.

Here is an example:

{
    ...

    "Features": {
        ...

        "Shell": {
            "InterpreterPath": "/bin/bash",
            "Unrestricted": true
        },
        ...
    },

    ...
}

Usage

Use any capable laitos daemon to invoke the app:

.s shell-command

The shell command may use shell interpreter's capabilities to their full extend. For example, the following command will find system users whose name contains "howard" and store them in an output file:

.s cat /etc/passwd | grep howard > output.txt

Tips

• When InterpreterPath is left empty, laitos will automatically look for a shell interpreter from /bin, /usr/bin, /usr/local/bin, /opt/bin, laitos recognises bash, dash, zsh, ksh, ash, tcsh, csh, sh.
• On Windows, laitos uses PowerShell by default, unless an alternative shell interpreter is specified in configuration.
• On Linux, the PATH is hard-coded to /tmp/laitos-util:/bin:/sbin:/usr/bin:/usr/sbin:/usr/libexec:/usr/local/bin:/usr/local/sbin:/opt/bin:/opt/sbin when executing shell commands.
• laitos automatically copies some non-essential executables such as busybox and toybox into /tmp/laitos-util.