def set_dns(name, dnsservers=None, searchdomains=None, path=None):
    '''
    .. versionchanged:: 2015.5.0
        The ``dnsservers`` and ``searchdomains`` parameters can now be passed
        as a comma-separated list.

    Update /etc/resolv.confo

    path

        path to the container parent
        default: /var/lib/lxc (system default)

        .. versionadded:: 2015.8.0

    CLI Example:

    .. code-block:: bash

        salt myminion lxc.set_dns ubuntu "['8.8.8.8', '4.4.4.4']"

    '''
    if dnsservers is None:
        dnsservers = ['8.8.8.8', '4.4.4.4']
    elif not isinstance(dnsservers, list):
        try:
            dnsservers = dnsservers.split(',')
        except __HOLE__:
            raise SaltInvocationError(
                'Invalid input for \'dnsservers\' parameter'
            )
    if searchdomains is None:
        searchdomains = []
    elif not isinstance(searchdomains, list):
        try:
            searchdomains = searchdomains.split(',')
        except AttributeError:
            raise SaltInvocationError(
                'Invalid input for \'searchdomains\' parameter'
            )
    dns = ['nameserver {0}'.format(x) for x in dnsservers]
    dns.extend(['search {0}'.format(x) for x in searchdomains])
    dns = '\n'.join(dns) + '\n'
    # we may be using resolvconf in the container
    # We need to handle that case with care:
    #  - we create the resolv.conf runtime directory (the
    #   linked directory) as anyway it will be shadowed when the real
    #   runned tmpfs mountpoint will be mounted.
    #   ( /etc/resolv.conf -> ../run/resolvconf/resolv.conf)
    #   Indeed, it can save us in any other case (running, eg, in a
    #   bare chroot when repairing or preparing the container for
    #   operation.
    #  - We also teach resolvconf to use the aforementioned dns.
    #  - We finally also set /etc/resolv.conf in all cases
    rstr = __salt__['test.rand_str']()
    # no tmp here, apparmor won't let us execute !
    script = '/sbin/{0}_dns.sh'.format(rstr)
    DNS_SCRIPT = "\n".join([
        # 'set -x',
        '#!/usr/bin/env bash',
        'if [ -h /etc/resolv.conf ];then',
        ' if [ "x$(readlink /etc/resolv.conf)"'
        ' = "x../run/resolvconf/resolv.conf" ];then',
        '  if [ ! -d /run/resolvconf/ ];then',
        '   mkdir -p /run/resolvconf',
        '  fi',
        '  cat > /etc/resolvconf/resolv.conf.d/head <<EOF',
        dns,
        'EOF',
        '',
        ' fi',
        'fi',
        'cat > /etc/resolv.conf <<EOF',
        dns,
        'EOF',
        ''])
    result = run_all(
        name, 'tee {0}'.format(script), path=path,
        stdin=DNS_SCRIPT, python_shell=True)
    if result['retcode'] == 0:
        result = run_all(
            name, 'sh -c "chmod +x {0};{0}"'.format(script),
            path=path, python_shell=True)
    # blindly delete the setter file
    run_all(name,
            'sh -c \'if [ -f "{0}" ];then rm -f "{0}";fi\''.format(script),
            path=path, python_shell=True)
    if result['retcode'] != 0:
        error = ('Unable to write to /etc/resolv.conf in container \'{0}\''
                 .format(name))
        if result['stderr']:
            error += ': {0}'.format(result['stderr'])
        raise CommandExecutionError(error)
    return True
dataset/ETHPy150Open saltstack/salt/salt/modules/lxc.py/set_dns