# systemd-journal() source options The `systemd-journal()` driver has the following options: ## chain-hostnames() | ---|--- Accepted values: | `yes`, `no` Default: | `no` _Description:_ Enable or disable the chained hostname format. For details, see the [chain-hostnames() global option](../../../docs/axosyslog-core/4.26/chapter-global-options/reference-options/index.md#global-options-chain-hostnames). ## default-facility() | ---|--- Type: | facility string Default: | local0 _Description:_ The default facility value if the SYSLOG_FACILITY entry does not exist. ## default-level() | ---|--- Type: | string Default: | notice _Description:_ The default level value if the PRIORITY entry does not exist. ## default-priority() | ---|--- Type: | priority string Default: | notice _Description:_ This parameter assigns a severity to the messages received from the source if the message does not specify one. For example, `default-priority(warning)`. ## default-severity() | ---|--- Type: | severity string Default: | `notice` _Description:_ Assigns a default severity to messages received from this source when the message doesn’t specify one. Accepts the standard syslog severity keywords (for example, `emerg`, `alert`, `crit`, `err`, `warning`, `notice`, `info`, `debug`). Combined with `default-facility()` to compute the message priority. ## dns-cache() | ---|--- Accepted values: | `yes`, `no` Default: | `no` _Description:_ Enable or disable DNS cache usage. ## hook-commands() _Description:_ This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The `hook-commands()` can be used with all source and destination drivers with the exception of the `usertty()` and `internal()` drivers. Note The AxoSyslog application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable AxoSyslog to execute external applications. ### Using `hook-commands()` when AxoSyslog starts or stops To execute an external program when AxoSyslog starts or stops, use the following options: #### `startup()` Type: | string ---|--- Default: | N/A _Description:_ Defines the external program that is executed as AxoSyslog starts. #### `shutdown()` Type: | string ---|--- Default: | N/A _Description:_ Defines the external program that is executed as AxoSyslog stops. ### Using the hook-commands() when AxoSyslog reloads To execute an external program when the AxoSyslog configuration is initiated or torn down, for example, on startup/shutdown or during a AxoSyslog reload, use the following options: #### `setup()` Type: | string ---|--- Default: | N/A _Description:_ Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload. #### `teardown()` Type: | string ---|--- Default: | N/A _Description:_ Defines an external program that is executed when the AxoSyslog configuration is stopped or torn down, for example, on shutdown or during a AxoSyslog reload. ### Example: Using hook-commands() with a network source In the following example, the `hook-commands()` is used with the `network()` driver and it opens an [iptables]( "https://en.wikipedia.org/wiki/Iptables") port automatically as AxoSyslog is started/stopped. The assumption in this example is that the `LOGCHAIN` chain is part of a larger ruleset that routes traffic to it. Whenever the AxoSyslog created rule is there, packets can flow, otherwise the port is closed. Terminal window ``` source { network(transport(udp) hook-commands(           startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")           shutdown("iptables -D LOGCHAIN 1")         )      ); }; ``` ## host-override() | ---|--- Type: | string Default: | _Description:_ Replaces the ${HOST} part of the message with the parameter string. ## internal() | ---|--- Accepted values: | `yes`, `no` Default: | `no` _Description:_ Marks this pipeline element as internal. Elements marked as `internal()` are treated as an implementation detail, so for example statistics of the given pipe are available only on higher stats level. This option is mainly useful for developers or when writing SCL blocks and integrations. ## keep-hostname() | ---|--- Type: | yes or no Default: | no _Description:_ Enable or disable hostname rewriting. * If enabled (`keep-hostname(yes)`), AxoSyslog will retain the hostname information read from the systemd journal messages. * If disabled (`keep-hostname(no)`), AxoSyslog will use the hostname that has been set up for the operating system instance that AxoSyslog is running on. To query or set this value, use the `hostnamectl` command. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available. ## keep-timestamp() | ---|--- Type: | yes or no Default: | yes _Description:_ Specifies whether AxoSyslog should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available. Warning To use the `S_` macros, the `keep-timestamp()` option must be enabled (this is the default behavior of AxoSyslog). ## log-fetch-limit() | ---|--- Type: | number Default: | 100 _Description:_ The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if `log-fetch-limit()` is too high. ## log-iw-size() | ---|--- Type: | number Default: | 100 _Description:_ Specifies the source window size - the maximum number of in-flight messages permitted by the source before flow control is enforced. This only applies when `flow-control` is enabled. **CAUTION:** If you change the value of `log-iw-size()` and `keep-alive()` is enabled, the change will affect only new connections, the `log-iw-size()` of kept-alive connections will not change. To apply the new `log-iw-size()` value to every connection, [restart the `syslog-ng` service](../../../docs/axosyslog-core/4.26/quickstart/managing-and-checking-linux/index.md#restart-axosyslog). A simple configuration reload is _NOT_ sufficient. If the source is receiving data using the UDP protocol, always [restart the `syslog-ng` service](../../../docs/axosyslog-core/4.26/quickstart/managing-and-checking-linux/index.md#restart-axosyslog) after changing the value of `log-iw-size()` for the changes to take effect. Note that when using `disk-buffer()`, the messages stored on disk are not included in the window size calculation. For details about the effects of this parameter, see [Managing incoming and outgoing messages with flow-control](../../../docs/axosyslog-core/4.26/chapter-routing-filters/concepts-flow-control/index.md). ## log-prefix() (DEPRECATED) | ---|--- Type: | string Default: | This option is deprecated. Use `program-override` instead. _Description:_ A string added to the beginning of every log message. It can be used to add an arbitrary string to any log source, though it is most commonly used for adding `kernel:` to the kernel messages on Linux. ## long-hostnames() Obsolete alias for [`chain-hostnames()`](../../../docs/axosyslog-core/4.26/chapter-global-options/reference-options/index.md#global-options-chain-hostnames). \--> ## match-boot() | ---|--- Type: | `yes`, `no` Default: | no Available in AxoSyslog 4.1 and later. _Description:_ If set to yes, AxoSyslog fetches only journal messages that relate to the current boot, and to ignores messages generated in previous boots. ## matches() | ---|--- Type: | arrow list Default: | Available in AxoSyslog 4.1 and later. _Description:_ Specifies one or more filters to apply on the journal fields, similarly how you can use `journalctl`. For example: Terminal window ``` matches( "_COMM" => "systemd" ) ``` ## max-field-size() | ---|--- Type: | number (characters) Default: | 65536 _Description:_ The maximum length of a field’s value. ## namespace() | ---|--- Type: | string Default: | “*” _Description:_ The `namespace()` option works exactly the same way as [the respective option of the Journalctl command line tool](). The following modes of operation are available: * If you do not specify the `namespace()` option in your configuration, or if you specify an empty string, the `systemd-journal()` source reads and displays log data from all namespaces. * If you specify the `namespace()` option as `namespace("*")`, the `systemd-journal()` source reads and displays log data from all namespaces, interleaved. * If `namespace()` is specified, the `systemd-journal()` source only reads and displays log data from the specified namespace. * If the namespace identifier is prefixed with `"+"` when you specify your `namespace()` option, the `systemd-journal()` source only reads and displays log data from the specified namespace and the default namespace, interleaved. Starting with AxoSyslog 4.4, you can use multiple `systemd-journal()` sources in your configuration. In this case, each source must use unique systemd namespaces. _Syntax:_ `namespace(string)` ### Example: configuration examples for using the namespace() option The following configuration example uses the default value for the `namespace()` option: Terminal window ``` source s_journal { systemd-journal(namespace("*")); }; ``` The following configuration example uses a prefixed namespace identifier in the `namespace()` option: Terminal window ``` source s_journal { systemd-journal(namespace("+foobar")); }; ``` Note Namespace support was introduced to the Journalctl command line tool in Systemd version 2.45. The AxoSyslog application supports the `namespace()` option from version 3.29. For further information about namespaces on the Systemd side, see [Journal Namespaces](). ## normalize-hostnames() | ---|--- Accepted values: | `yes`, `no` Default: | `no` _Description:_ If enabled (`normalize-hostnames(yes)`), AxoSyslog converts the hostnames to lowercase. Note ``` This setting applies only to hostnames resolved from DNS. It has no effect if the keep-hostname() option is enabled, and the message contains a hostname. ``` ## persist-name() | ---|--- Type: | string Default: | N/A _Description:_ If you receive the following error message during AxoSyslog startup, set the `persist-name()` option of the duplicate drivers: Terminal window ``` Error checking the uniqueness of the persist names, please override it with persist-name option. Shutting down. ``` This error happens if you use identical drivers in multiple sources, for example, if you configure two file sources to read from the same file. In this case, set the `persist-name()` of the drivers to a custom string, for example, `persist-name("example-persist-name1")`. ## prefix() | ---|--- Type: | string Default: | .journald. _Description:_ If this option is set, every non-built-in mapped names get a prefix (for example: `".SDATA.journald."`). By default, AxoSyslog adds the `.journald.` prefix to every value. ## program-override() | ---|--- Type: | string Default: | _Description:_ Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the `program-override("kernel")` option in the source containing `/proc/kmsg`. ## read-old-records() | ---|--- Type: | `yes` or `no` Default: | yes _Description:_ If set to `yes`, AxoSyslog will start reading the records from the beginning of the file/journal, if the file/journal has not been read yet. If set to `no`, AxoSyslog will read only the new records. If the source has a state in the persist file, this option will have no effect. ## tags() | ---|--- Type: | string Default: | _Description:_ Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example, `tags("dmz", "router")`. This option is available only in version 3.1 and later. ## time-zone() | ---|--- Type: | name of the timezone, or the timezone offset Default: | _Description:_ The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself. The timezone can be specified by using the name, for example, `time-zone("Europe/Budapest")`), or as the timezone offset in +/-HH:MM format, for example, `+01:00`). On Linux and UNIX platforms, the valid timezone names are listed under the `/usr/share/zoneinfo` directory. ## use-dns() | ---|--- Type: | `yes`, `no`, `persist_only` Default: | `yes` _Description:_ Enable or disable DNS usage. The `persist_only` option attempts to resolve hostnames locally from a file (for example, from `/etc/hosts`) set using the [`dns-cache-hosts()` global option](../../../docs/axosyslog-core/4.26/chapter-global-options/reference-options/index.md#global-option-dns-cache-hosts). The AxoSyslog application blocks on DNS queries, so enabling DNS may lead to a Denial of Service attack. To prevent DoS, protect your AxoSyslog network endpoint with firewall rules, and make sure that all hosts which may get to AxoSyslog are resolvable. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available. For details on configuring local DNS resolution, see [Using name resolution in syslog-ng](../../../docs/axosyslog-core/4.26/chapter-examples/examples-dns/index.md). Note ``` This option has no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname. ``` ## use-fqdn() | ---|--- Type: | yes or no Default: | no _Description:_ Use this option to add a Fully Qualified Domain Name (FQDN) instead of a short hostname. You can specify this option either globally or per-source. The local setting of the source overrides the global option if available. Note Set `use-fqdn()` to `yes` if you want to use the `custom-domain()` global option. Note This option has no effect if the `keep-hostname()` option is enabled (`keep-hostname(yes)`) and the message contains a hostname. ## use-syslogng-pid() | ---|--- Type: | `yes`, `no` Default: | `no` _Description:_ When enabled, AxoSyslog overrides the PID from the original message with the PID of the `syslog-ng` process. Last modified May 8, 2026: [Renames hook-commands snippet (473feff3)]()