btrfs plugin for nagios compatible monitoring systems

 This nagios compatible monitoring plugin will check available space and error
 statistics of a btrfs filesystem.
 .
 Traditional space usage monitoring based on the output of df is not sufficient
 when using btrfs. This plugin takes allocated but unused disk space, and
 unallocatable disk space (for example when mixing different sized disks with
 raid profiles) into account. It is meant to be used as an addition to using a
 regular disk usage plugin, based on df output.
 .
 Additionally, the check keeps an eye on device error stats and will report if
 any of the counters (read errors, write errors, etc) of a device that is part
 of the filesystem is not zero.