Watchdog: Disk Space

Monitors the usage of a mount point in percent with warn and fail thresholds. Type disk_space, runner Agent. Fields, defaults, statuses and messages.

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Watchdog: Disk Space

The check reads total and free space of a path and calculates the usage in percent.

Property	Value
Type identifier	`disk_space`
Runner	Agent
Target in the email	`Path`

Fields

Field	Key	Default	Meaning
Mount path	`path`	`/`	Required. Absolute path of the mount point, for example `/`, `/var` or `/mnt/backup`
Warn threshold (%)	`warn_percent`	`80`	`WARN` from this usage
Fail threshold (%)	`fail_percent`	`90`	`FAIL` from this usage. Must be greater than the warn threshold

Behaviour

If the environment variable HOST_ROOT is set in the agent, the check prepends it to the path. /var then becomes /host/root/var. Usage is (total - free) / total, rounded to whole percent. It can therefore differ slightly from the Use% column of df.

Situation	Status	Message
Usage below the warn threshold	`OK`	`<n>% used (<free> free of <total>)`
Usage at or above the warn threshold	`WARN`	`<n>% used (<free> free of <total>)`
Usage at or above the fail threshold	`FAIL`	`<n>% used (<free> free of <total>)`
Path does not exist or is not a directory	`UNKNOWN`	`Path not found or not a directory: <path>`
Fail threshold not greater than warn threshold	`UNKNOWN`	`Invalid config: fail_percent must be greater than warn_percent`
Total size cannot be determined	`UNKNOWN`	`Cannot determine total disk space for <path>`
Read error	`FAIL`	`Cannot read disk space for path: <resolved path>`
No path configured	`UNKNOWN`	`No path configured`

Sizes appear in KB, MB or GB.

The messages Path not found or not a directory and Cannot determine total disk space show the configured path, for example /var. The read-error message instead contains the resolved path with the HOST_ROOT prefix, for example /host/root/var.

The agent needs the volume /:/host/root:ro and HOST_ROOT=/host/root, otherwise the check measures the filesystem inside the agent container, see Agents.