I read about a bunch of interesting Linux related technologies.

Today, I was looking for something interesting to write about, without spending too much time on. Because I wanted to reserve my time for a dev project. Obviously, I failed, as it is pretty late here, and I just started writing the post.

So, what happened.

I have this general notes file, which is, you guessed it, an emacs org-mode file.

In it, I have a “Learn” section. This is just a list of technologies/concepts that I found interesting or useful to explore in the future. Here are a few example entries:

UMCG? What is that? I had no description in the file. Quick googling didn’t produce any results that sounded relevant to my domain either.


It took a while to find out that it stands for: User-Managed Concurrency Groups.

According to this LKML post1 from 2021, UMCG is a proposed Linux Kernel feature, as part of the work to open-source the “Google Fibers” userspace scheduling framework.

I don’t quite know how learning more about this would be useful to me, but it sounded like a cool concept.

A quick grep on the recent kernel release (6.7) sources didn’t produce any results. My understanding is, this concept haven’t been merged yet. It seems like there have been a few iterations on the implementation, and the last UMCG related discussion I found is from last year.


Then I ended up reading a bunch of other discussions on LKML.

In one of the posts, I encountered another four letter acronym that’s more familiar: CRIU

This is the second time in 2 days I am encountering CRIU. CRIU is “a project to implement checkpoint/restore functionality for Linux”. It stands for “Checkpoint/Restore In Userspace”.

I read about it yesterday, while trying to figure out what other features LXC provides. LXC has an lxc-checkpoint command that (according to the man page, since I couldn’t test it) allows checkpointing and restoring a container. It uses CRIU internally.

CRIU looks like a pretty ambitious and interesting project. I am not sure how successful or stable it is, but it is already integrated in a bunch of software. The wiki pages I found to be insightful are:

I just started following the tutorials to have a better understanding of this technology, and the limitations.

And that’s it for today. Thanks for reading! If you find technical errors, please report in the blog’s Issues page.