Hide navigation sidebar
Hide table of contents sidebar
Back to top
Toggle table of contents sidebar

# Daemon behavior

This specification covers some of the Incus daemon’s behavior.

## Startup

On every start, Incus checks that its directory structure exists. If it doesn’t, it creates the required directories, generates a key pair and initializes the database.

Once the daemon is ready for work, Incus scans the instances table for any instance for which the stored power state differs from the current one. If an instance’s power state was recorded as running and the instance isn’t running, Incus starts it.

## Signal handling

### `SIGINT`, `SIGQUIT`, `SIGTERM`

For those signals, Incus assumes that it’s being temporarily stopped and will be restarted at a later time to continue handling the instances.

The instances will keep running and Incus will close all connections and exit cleanly.

### `SIGPWR`

Indicates to Incus that the host is going down.

Incus will attempt a clean shutdown of all the instances. After 30 seconds, it kills any remaining instance.

The instance `power_state` in the instances table is kept as it was so that Incus can restore the instances as they were after the host is done rebooting.

### `SIGUSR1`

Write a memory profile dump to the file specified with `--memprofile`.