FreeNAS Naemon/Icinga/Nagios plugin.

Tested with: Naemon 1.0.5, 1.0.6; Ruby 2.3.0, 2.3.3; FreeNAS 9.10.2


Some checks are executed via SSH (see below). For this the net-ssh gem is necessary.

gem install net-ssh


check_freenas v0.2.0 []

This plugin checks various parameters of FreeNAS

    alerts                  Notifies of alerts
    updates                 Check if update is available
  ZFS Zpool:
    zpool_usage             Checks zpool usage in percentage
  ZFS Dataset:
    datasets_usage          Checks used space of all datasets in megabytes. Exclude and include like: "-x ds1,ds2" or "-i ds1,ds2"
    dataset_quota           Checks dataset quota usage in percentage
  ARC Cache:
    arc_cache_miss_ratio    Checks ARC miss ratio
    arc_cache_meta_usage    Checks ARC metadata usage against metadata limit
    arc_cache_mru_ghost     Checks ARC most recently used ghost hits
    arc_cache_mfu_ghost     Checks ARC most frequently used ghost hits
  I/O,Disk Statistics:
    io_requests_pending     Checks pending io requests via gstat
    disk_busy               Checks disk busy usage via gstat

Usage: check_freenas.rb [options]

    -s, --address ADDRESS            FreeNAS host address
    -u, --username USERNAME          Username to connect - only root possible
    -p, --password PASSWORD          Password for user
    -k, --insecure                   No SSL verification
    -m, --mode MODE                  Mode to check
    -z, --zpool ZPOOL                Zpool name
    -d, --dataset DATASET            Dataset name
    -i, --include INCLUDE            Include dataset
    -x, --exclude EXCLUDE            Exclude dataset
    -w, --warning WARNING            Warning threshold
    -c, --critical CRITICAL          Critical threshold
    -v, --version                    Print version information
    -h, --help                       Show this help message


  • -s: FreeNAS host,, mandatory
  • -u: username, mandatory
  • -k: if you've a self signed cert
  • -z: zpool name
  • -d: dataset name
  • -i: only use this dataset, multiple values seperated with comma e.g. home,data,test
  • -x: exclude dataset, multiple values seperated with comma e.g. home,data,test



Following checks are performed via the FreeNAS API (v1). Only https and user root is possible.


Check outstanding alerts.

./check_freenas.rb -s -u root -p  [-k] -m alerts
Warning - smartd is not running


Notifies of available updates.

./check_freenas.rb -s -u root -p  [-k] -m updates
Warning - There are pending updates. Go to System > Update to apply pending updates

Datasets usage

Check used space in MB of all datasets with perfdata. Use include/exclude option to limit output.

./check_freenas.rb -s -u root -p  [-k] -m datasets_usage -z tank -i data,home -w 1176000 -c 1185555
Warning - Dataset data used 1176133MB | home=910786MB;1176000;1185555 data=1176133MB;1176000;1185555

Zpool usage

Checks Zpool usage in percentage with perfdata.

./check_freenas.rb -s -u root -p  [-k] -m zpool_usage -w 30 -c 40 -z tank
OK - tank: usage 60% | tank=60%;70;80


Following checks are performed through SSH via net-ssh to the FreeNAS host. SSH connection is initiated from the host who executes the plugin.

Dataset quota

Check used space against refquota value. Output will be in percentage (float) with perfdata.

./check_freenas.rb -s -u  -p  -m dataset_quota_usage -w 70 -c 80 -d 'tank/data
Critical - tank/data: usage 85.98% | tank/data=85.98%;30;40

ARC Cache

Checks various kstat values. Output will be in percentage (float) with perfdata.

Miss ratio

./check_freenas.rb -s -u  -p  -m arc_cache_miss_ratio -w 60 -c 70
Critical - ARC cache miss ratio: 70.72% | arc_cache_miss_ratio=70.72%;60;70

Metadata usage

./check_freenas.rb -s -u  -p  -m arc_cache_meta_usage -w 60 -c 70
OK - ARC cache metadata usage: 19.61% | arc_cache_meta_usage=19.61%;60;70

MRU ghost hits

./check_freenas.rb -s -u  -p  -m arc_cache_mru_ghost -w 10 -c 15
OK - ARC cache mru ghost hits: 0.02% | arc_cache_mru_ghost=0.02%;10;15

MFU ghost hits

./check_freenas.rb -s -u  -p  -m arc_cache_mfu_ghost -w 10 -c 15
OK - ARC cache mfu ghost hits: 2.46% | arc_cache_mfu_ghost=2.46%;10;15

IO requests pending

Checks pending io in queue via gstat from all physical disks that are at least 0.1% busy.

./check_freenas.rb -s -u  -p  -m io_requests_pending -w 5 -c 10
OK - ada0: 0, da0: 0, da18: 0, da22: 0, da24: 0, da25: 0, da27: 1, da28: 0, da30: 0, da32: 0, da33: 0 | ada0=0;5;10 da0=0;5;10 da18=0;5;10 da22=0;5;10 da24=0;5;10 da25=0;5;10 da27=1;5;10 da28=0;5;10 da30=0;5;10 da32=0;5;10 da33=0;5;10

Disk busy

Checks disk busy value via gstat from all physical disks that are at least 0.1% busy.

./check_freenas.rb -s -u  -p  -m disk_busy -w 40 -c 50
OK - ada0: 0.3%, da0: 0.3%, da21: 1.6%, da22: 0.6%, da25: 1.7%, da26: 3.1%, da28: 1.3%, da30: 1.3%, da31: 0.5%, da33: 1.0% | ada0=0.3%;40;50 da0=0.3%;40;50 da21=1.6%;40;50 da22=0.6%;40;50 da25=1.7%;40;50 da26=3.1%;40;50 da28=1.3%;40;50 da30=1.3%;40;50 da31=0.5%;40;50 da33=1.0%;40;50