Lifecycle hooks

lookout can run a command inside a container immediately before it stops the container for an update, and again immediately after it starts the recreated container. Unlike Watchtower, lookout has no global enable flag. A hook runs only if the corresponding label is present on the container, so hooks are opt-in by construction.

Type	Docker container label
Pre-update	io.lookout.lifecycle.pre-update
Post-update	io.lookout.lifecycle.post-update

docker run -d \
  --label io.lookout.lifecycle.pre-update="/dump-data.sh" \
  --label io.lookout.lifecycle.post-update="/restore-data.sh" \
  someimage

The command runs via docker exec … /bin/sh -c "<command>", so the container needs a sh executable. If the container is not running, its hooks cannot run, and the update proceeds without them.

lookout logs a non-zero exit code as a warning, but does not stop the update because of it.

Not implemented

• Pre-check / post-check hooks. Watchtower runs these around the staleness check itself (not just the update). lookout does not implement these at all.
• Per-hook timeouts. Watchtower kills a hook after 60s by default (configurable per-label). lookout's hook execution has no timeout — a hanging hook command blocks that container's update indefinitely.