config refactoring: use runtime config

[trawler]

Signed-off-by: Karen Almog [email protected]

Issue
Fixes #1202 #1261
What this PR Includes
This PR refactors the entire handling of k0s config. Among other changes it:

1. Removes --config as a global flag to all commands
2. Keeps --config flag only on the k0s controller and k0s reset commands (note on the reset command below).
3. Adds a default value to k0s config: /etc/k0s/k0s.yaml
4. Generates a runtime config whenever k0s controller goes up and keeps it under /run/k0s/k0s.yaml. This runtime config file is removed when the controller is stopped.
5. The runtime config is a merged config of custom values and default config values (show merged config #1261)

Note on k0s reset:
Since the runtime config only exists while the controller is up, k0s reset (that can only be performed while the controller is down) needs to still retail the --config flag. A workaround to that would be to use the global location /etc/k0s/k0s.yaml as a source of configuration.

To Do:

• Resolve correct runtime config file for single nodes
• When validating config against a non-existent path, the output is silent #1354
• Fix prerun validate logic

[jnummelin]

Left some questions and general comments. The direction is good in general.

I'm slightly worried that dropping the -config option in many commands will break backwards compatibility e.g. with k0sctl. Maybe rebase with the #1450 to verify this.

[kke]

Left some questions and general comments. The direction is good in general.

I'm slightly worried that dropping the -config option in many commands will break backwards compatibility e.g. with k0sctl. Maybe rebase with the #1450 to verify this.

You could leave a nonfunctional hidden --config flag, maybe it could warn but ignore.

[trawler]

Left some questions and general comments. The direction is good in general.

I'm slightly worried that dropping the -config option in many commands will break backwards compatibility e.g. with k0sctl. Maybe rebase with the #1450 to verify this.

k0sctl requires a very minor change for token creation. after that, make check-k0sctl passes: https://github.com/k0sproject/k0sctl/compare/main...trawler:k0s_config_flag_1409?expand=1

[trawler]

Waiting for next k0sctl that includes k0sproject/k0sctl#303 to run the make check-k0sctl test again

[kke]

It looks ok to me but it's fairly big and touches everything so I think the best would be to get it in as soon as possible before a release that includes it so that there is time to find any problems.