Set host values based on event data
You can configure Splunk software to assign host names to your events based on the data in those events. This topic shows you how to use event data to override default host assignments with props.conf and transforms.conf and regular expressions.
For a primer on regular expression syntax and usage, see Regular-Expressions.info. You can test regular expressions by using them in searches with the rex search command. The Splunk community wiki also has a list of useful third-party tools for writing and testing regular expressions.
To configure per-event overrides, you need to create two stanzas, one in
transforms,conf <and another in props.conf. Edit these files in
$SPLUNK_HOME/etc/system/local/ or in your own custom application directory in
$SPLUNK_HOME/etc/apps/. If you have Splunk Cloud, edit these settings on the machines where you run the Splunk universal forwarder. For more information about configuration files in general, see About configuration files in the Splunk Enterprise Admin Manual.
Create a stanza in
transforms.confthat follows this syntax:
[<unique_stanza_name>] REGEX = <your_regex> FORMAT = host::$1 DEST_KEY = MetaData:Host
Note the following:
<unique_stanza_name>should reflect that it involves a host value. You'll use this name later in the
<your_regex>is a regular expression that identifies where in the event you want to extract the host value.
FORMAT = host::$1writes the
REGEXvalue into the
Next, create a stanza in
props.confthat references the
[<spec>] TRANSFORMS-<class> = <unique_stanza_name>
Note the following:
<sourcetype>, the source type of an event.
<host>is the host value for an event.
<source>is the source value for an event.
<class>is any unique identifier that you want to give to your transform.
<unique_stanza_name>is the name of the stanza you created in
Assume that you're starting with the following set of events from the
houseness.logfile. The host is in the third position ("fflanda", etc.).
41602046:53 accepted fflanda 41602050:29 accepted rhallen 41602052:17 accepted fflanda
First, create a new stanza in
transforms.confwith a regular expression that extracts the host value:
[houseness] DEST_KEY = MetaData:Host REGEX = \s(\w*)$ FORMAT = host::$1
Next, reference your
transforms.confstanza in a
props.confstanza. For example:
[source::.../houseness.log] TRANSFORMS-rhallen=houseness SHOULD_LINEMERGE = false
The above stanza has the additional attribute/value pair
SHOULD_LINEMERGE = false, to break events at each newline.
The events will now appear in search results like this:
Set a default host for a file or directory input
Change host values after indexing
This documentation applies to the following versions of Splunk Cloud™: 7.1.3, 7.1.6, 7.2.3, 7.2.4, 7.2.6, 7.2.7, 7.2.8, 7.2.9, 8.0.0, 8.0.1