The check queries the state of a container through the Docker socket /var/run/docker.sock. It evaluates Running and, if the container defines a HEALTHCHECK, its status.
| Property | Value |
|---|---|
| Type identifier | docker |
| Runner | Dashboard or Agent |
| Target in the email | Container |
| Field | Key | Default | Meaning |
|---|---|---|---|
| Container name | container_name |
Required. Exact container name as printed by docker ps --format "{{.Names}}" |
| Situation | Status | Message |
|---|---|---|
Running, HEALTHCHECK reports healthy |
OK |
healthy |
Running, no HEALTHCHECK defined |
OK |
running |
Running, HEALTHCHECK reports starting |
UNKNOWN |
starting |
Running, HEALTHCHECK reports unhealthy |
WARN |
unhealthy |
| Running, any other health status | FAIL |
the status |
| Not running | FAIL |
Container "<name>" is not running |
| Container not found or API error | FAIL |
Docker API error: Container not found (404) or another error |
| Socket missing | UNKNOWN |
Docker socket not available at /var/run/docker.sock |
| No container name | UNKNOWN |
No container_name configured |
The Docker socket must be mounted in the container that runs the check:
group_add: DOCKER_GID.The socket gives access to the Docker daemon API. Even when mounted read-only (
:ro), containers can be controlled through it. Mount it only where you really need Docker checks.