The memory check (check_memory) checks the available memory as reported by the OS. It queries the OS for the amount of available memory, the amount of free memory, then calculates a memory used percentage. That memory used percentage is then compared against the --warning and --critical thresholds and an appropriate check result is output.
Flags
--warning: The percentage of used memory required to trigger a warning condition. Default 85.
--critical: The percentage of used memory required to trigger a critical condition. Default 95.
--metric_name: The name used in the nagios portion of the message output. Default memory_used_percentage.
Examples
Issue a warning if memory usage is over 50% and critical if usage is over the default of 95%.