systemd: Update to 255

[pothos]

The new version will come out soon and it would be good to have it in main.
Since we are quite behind I think we should directly update to the latest version. In the past we thought that having a Flatcar release with a version in-between available would help with finding the point of a regression but I doubt it's really that helpful because things get backported for systemd stable releases anyway. Also it would mean to do 3 version updates where 2 are not used in the end.

[pothos]

Note: For the breaking changes I know that we have to fix some generators in the initrd not to write files outside of the generator folder.

[tormath1]

Note: The version 255 brings the EXTENSION_MANAGER_RELOAD feature. We should be able to drop the ensure-sysext.service (flatcar/init#96) and set this variable in our sysext images.

[ader1990]

Hello,

Just FYI: While trying to check if systemd 255 might fix #1336, I saw that the changes required to switch are pretty important, as 255 does not support split-usr anymore. Also, while trying to switch to 254, the changes conflcited with the baselayout in some of the files. Will update this issue once I have a working version.

[ader1990]

@sayanchowdhury @krnowak I started the systemd 255 patch series with the dracut upgrade, as it is required by systemd 255: flatcar/scripts#1665

After this PR gets merged, we can continue with a new PR for the systemd 255 upgrade.

I have a draft PR here for the systemd 255 that was created as a PoC to showcase that an image build is possible: flatcar/scripts#1664

[ader1990]

Note: The version 255 brings the EXTENSION_MANAGER_RELOAD feature. We should be able to drop the ensure-sysext.service (flatcar/init#96) and set this variable in our sysext images.

hello @tormath1, anything that can be done in this PR flatcar/scripts#1679 concerning the code from PR flatcar/init#96?

[tormath1]

@ader1990 I was thinking about it. If we just merge the flatcar/init#96 things are going to break I guess because the EXTENSION_MANAGER_RELOAD is not set on the image that we provide (bakery and built-in)