def add_journal(self, units=None, boot=None, since=None, until=None,
                    lines=None, allfields=False, output=None, timeout=None,
                    identifier=None, catalog=None, sizelimit=None, pred=None):
        """Collect journald logs from one of more units.

        :param units: A string, or list of strings specifying the
                       systemd units for which journal entries will be
                       collected.

        :param boot: A string selecting a boot index using the
                      journalctl syntax. The special values 'this' and
                      'last' are also accepted.

        :param since: A string representation of the start time for
                       journal messages.

        :param until: A string representation of the end time for
                       journal messages.

        :param lines: The maximum number of lines to be collected.

        :param allfields: A bool. Include all journal fields
                           regardless of size or non-printable
                           characters.

        :param output: A journalctl output control string, for
                        example "verbose".

        :param timeout: An optional timeout in seconds.
        :param identifier: An optional message identifier.
        :param catalog: Bool. If True, augment lines with descriptions
                        from the system catalog.
        :param sizelimit: Limit to the size of output returned in MB.
                          Defaults to the value of --log-size.
        """
        journal_cmd = "journalctl --no-pager "
        unit_opt = " --unit %s"
        boot_opt = " --boot %s"
        since_opt = " --since %s"
        until_opt = " --until %s"
        lines_opt = " --lines %s"
        output_opt = " --output %s"
        identifier_opt = " --identifier %s"
        catalog_opt = " --catalog"

        journal_size = 100
        all_logs = self.get_option("all_logs")
        log_size = sizelimit or self.get_option("log_size")
        log_size = max(log_size, journal_size) if not all_logs else 0

        if isinstance(units, six.string_types):
            units = [units]

        if units:
            for unit in units:
                journal_cmd += unit_opt % unit

        if identifier:
            journal_cmd += identifier_opt % identifier

        if catalog:
            journal_cmd += catalog_opt

        if allfields:
            journal_cmd += " --all"

        if boot:
            if boot == "this":
                boot = ""
            if boot == "last":
                boot = "-1"
            journal_cmd += boot_opt % boot

        if since:
            journal_cmd += since_opt % since

        if until:
            journal_cmd += until_opt % until

        if lines:
            journal_cmd += lines_opt % lines

        if output:
            journal_cmd += output_opt % output

        self._log_debug("collecting journal: %s" % journal_cmd)
        self._add_cmd_output(journal_cmd, timeout=timeout,
                             sizelimit=log_size, pred=pred)
Collect journald logs from one of more units.

        :param units: A string, or list of strings specifying the
                       systemd units for which journal entries will be
                       collected.

        :param boot: A string selecting a boot index using the
                      journalctl syntax. The special values 'this' and
                      'last' are also accepted.

        :param since: A string representation of the start time for
                       journal messages.

        :param until: A string representation of the end time for
                       journal messages.

        :param lines: The maximum number of lines to be collected.

        :param allfields: A bool. Include all journal fields
                           regardless of size or non-printable
                           characters.

        :param output: A journalctl output control string, for
                        example "verbose".

        :param timeout: An optional timeout in seconds.
        :param identifier: An optional message identifier.
        :param catalog: Bool. If True, augment lines with descriptions
                        from the system catalog.
        :param sizelimit: Limit to the size of output returned in MB.
                          Defaults to the value of --log-size.