Logging is a pervasive service across all other services. It consist of writing information to a (usually text) file and is generally handled by a program called syslog (currently syslog-ng) that takes logs through a socket or the network and writes them to files. Other software might also write their own logfiles, for example webservers do not write log files to syslog for performance reasons.

There's also a logging server that collects all those logfiles in a central location.


lnav is a powerful log parser that allows you to do interesting things on logfiles.

On any logfile, you can see per-second hit ratio by using the "histogram" view. Hit the i button to flip to the "histogram" view and z multiple times to zoom all the way into a per-second hit rate view. Hit q to go back to the normal view.

The lnav Puppet module can be used to install lnav and formats. Formats should be stored in the lnav module to make it easier to collaborate with the community.

Extending lnav formats

Known formats:

lnav also ships with its own set of default log formats, available in the source in src/default-log-formats.json. Those can be useful to extend existing log formats.