# internal() source options

The `internal()` driver has the following options:

## host-override()

|   
---|---  
Type: | string  
Default: |   
  
_Description:_ Replaces the ${HOST} part of the message with the parameter string.

## 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).

## normalize-hostnames()

|   
---|---  
Accepted values: | `yes`, `no`  
Default: | `no`  
  
_Description:_ If enabled (`normalize-hostnames(yes)`), AxoSyslog converts the hostnames to lowercase.

## 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`.

## 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.

## use-fqdn()

|   
---|---  
Type: | yes or no  
Default: | no  
  
_Description:_ Add Fully Qualified Domain Name instead of short hostname. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.

## 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 February 27, 2026: [Missing source options, part 2 (f88c63f6)](<https://github.com/axoflow/axosyslog-core-docs/commit/f88c63f653509edc883f6c58d5a404ca7f91ca32>)