cc_power_state_change should support kexec

This bug was originally filed in Launchpad as [LP: #1964998](https://bugs.launchpad.net/cloud-init/+bug/1964998)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = 2022-03-15T18:55:01.252063+00:00

date_created = 2022-03-15T18:42:50.251110+00:00

date_fix_committed = None

date_fix_released = None

id = 1964998

importance = medium

is_complete = True

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1964998

milestone = None

owner = bgermain1689

owner_name = Brendan Germain

private = False

status = opinion

submitter = bgermain1689

submitter_name = Brendan Germain

tags = ['bitesize']

duplicates = []

_Launchpad user **Brendan Germain(bgermain1689)** wrote on 2022-03-15T18:42:50.251110+00:00_

cc_power_state_change currently supports poweroff, halt, or reboot.

A way to call systemctl kexec or change the power cmd manually via an exposed attribute would be greatly beneficial.

The only workaround Im aware of today is calling systemctl kexec as your final runcmd but this doesn't allow cloud-init to cleanly finish/exit.

Start at the cc_power_state_change implementation and trace how the existing poweroff, halt, and reboot options finish cloud-init. Check how the requested systemctl kexec action would fit the power command handling, then verify that cloud-init can cleanly finish before kexec is invoked. Done means kexec is supported without requiring a final runcmd workaround.

Written by the indexing model from the issue text.