Implement configurable sentinel/reboot commands

[evrardjp]

I checked a few issues/PR, I can only notice that establishing a configurable sentinel and reboot command (see 1) would allow us to close a few other issues and PR:

• reboot not working: "Transport endpoint is not connected" #26
• Needs extension for Centos/RHEL distros #4
• CentOS reboot-required command support #77
• Request: images for other architectures #23 (comment)
• Parameterize the reboot function in order to be able to do other actions like shutdown for instance #31
• Parameterise reboot command #43
• Azure AKS Reboot failing - Error invoking reboot command: exit status 127 #44
• run script #59

[stuartpb]

If you're gathering use cases, I'll note that Kubic has a wide variety of alternatives to kured, like kexec: https://kubic.opensuse.org/documentation/man-pages/transactional-update.conf.5.html

[smueller18]

I have another use case for my cluster. Whenever kured reboots a node, the default alerts for ceph storage pods are firing for some minutes until the pods are ready again after the reboot.
The amtool binary can be used to silence alertmanager alerts. An example command to silence an alert is

amtool --alertmanager.url="http://localhost:9093" silence add --duration="30m" --author="kubernetes" --comment="reboot host" alertname="MyAlertName" host="$HOST"

It would be nice, if kured offers the ability to run such kinds of commands right before the reboot command is triggered.

I already though about alternatives, but none of them works:

• PreStop of kured pod hook executes amtool: runs always when the pod is terminated, not only on reboots by kured
• executes amtool by a systemd service on the host: not native kubernetes and runs also if not triggered by kured

[evrardjp]

If you're gathering use cases, I'll note that Kubic has a wide variety of alternatives to kured, like kexec: https://kubic.opensuse.org/documentation/man-pages/transactional-update.conf.5.html

These seem to be the target of a transactional update action, which means that transactional update action can call kured, and if kured is configured to call kexec, that would work... Sounds a tad complex though :)

[github-actions]

This issue was automatically considered stale due to lack of activity. Please update it and/or join our slack channels to promote it, before it automatically closes (in 7 days).

[evrardjp]

Curently stale, but we should keep this issue opened, as it's the way to track all the sub issues.

We just have prioritized the testing first.

[github-actions]

This issue was automatically considered stale due to lack of activity. Please update it and/or join our slack channels to promote it, before it automatically closes (in 7 days).

[anthr76]

kexec would be great! Any thoughts from a maintainer on opening this back up?

[evrardjp]

It's not only about kexec... !

But guess what?! It's implemented in our main branch (See also #297) ! It will be available on the next release, which should happen soon!