There's a closed pull request on the void-packages repository

runit: add support for SIGPWR signal
https://github.com/void-linux/void-packages/pull/20098

Description:
Hello!
This patch adds support for SIGPWR signal for runit. On receiving this signal runit gracefully shuts down machine.
This is needed for LXD containers running runit to shut down properly without any need for special configuration.
Seems like nothing else sends SIGPWR to process 0, so there should be no impact on normal operation, but some sort of testing should be done.
There was a huge conversation about it [here](https://www.mail-archive.com/supervision@list.skarnet.org/)