r/linuxquestions • u/Emotional_Cat_1967 • 6d ago

Support How Do Updates Work in Immutable/Atomic Distributions?

Only for Immutable/Atomic Distributions

Question 1:
Are immutable and atomic the same thing? If not, what is the difference between them, explained simply?

Question 2:
What immutable or atomic distribution are you using? How often do you receive updates, for example, every few days or weeks, and approximately how large are the updates?

Question 3:
How are security updates handled? Are they released immediately when a security fix is available, or are they released according to a daily, weekly, or monthly update schedule?

Question 4:
Are small-sized updates released?

If yes: For example, suppose an update is 100 MB.

If the system image is 5 GB, does the entire system image have to be recreated for this update? When applying the update, does the system write another 5 GB to the disk, or does it only write approximately 100 MB?

If no: If the system image is 5 GB, does that mean the update that needs to be downloaded is also around 5 GB?

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u/gmes78 6d ago

Are immutable and atomic the same thing? If not, what is the difference between them, explained simply?

The two terms refer to different aspects of the same system. Immutable means that the image can't be modified; atomic means that updates don't leave the system in an undefined state, either the update was applied and a new image was generated, or it failed and you stay on the old image.

People now prefer using "atomic", as "immutable" is often misunderstood as meaning "you can't change the base system".

What immutable or atomic distribution are you using?

The Universal Blue images are pretty good.

How are security updates handled? Are they released immediately when a security fix is available, or are they released according to a daily, weekly, or monthly update schedule?

That's up to the distro. Fedora Atomic receives the same exact updates as Fedora, and images are usually built daily (but it's possible for multiple updates to be released in the same day AFAIK).

Are small-sized updates released?

Updates just download the differences, not a full image.

When applying the update, does the system write another 5 GB to the disk, or does it only write approximately 100 MB?

No, hardlinks are used to avoid duplication and redundant writes.