Determine whether salt-minion is installed and, if not,
    install it.
    Return True if install is successful or already installed.

def _install(mpt):
    '''
    Determine whether salt-minion is installed and, if not,
    install it.
    Return True if install is successful or already installed.
    '''
    _check_resolv(mpt)
    boot_, tmppath = (prep_bootstrap(mpt)
             or salt.syspaths.BOOTSTRAP)
    # Exec the chroot command
    cmd = 'if type salt-minion; then exit 0; '
    cmd += 'else sh {0} -c /tmp; fi'.format(os.path.join(tmppath, 'bootstrap-salt.sh'))
    return not __salt__['cmd.run_chroot'](mpt, cmd, python_shell=True)['retcode']