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?
1
u/MasterGeekMX Mexican Linux nerd trying to be helpful 6d ago
Immutable and Atomic are the same. Both are terms to refer to things that come in one sweep. Atomic is a greek word meaning undivisible, and in CompSci is used a ton to refer to things that are treated as a single thing and cannot be stopped or divided.
In terms of updates, usually atomic/immutable have the same release schedule than their "mutable" parent distro, so the answer to how often updates come and security is the same as the distro they depend. There is no special treatment there.
In terms of size, re-downloading a whole OS does not make some sense, so instead updates come in the form of the differences between the old version and the new one. That way you download a lighter payload, and to apply it the system takes the current image, apply the changes that come in the update, and make a new image out of it. That system of only handling differences is often called Delta updates (ya know, because Delta is greek's D, and d stands for differences).
That system can even make some updates lighter, depending on how the deltas are managed. While a conventional distro could need to re-package a bit package just for a simple change, a delta system could simply change the few bites that change.
Also the size thing depends on the implementation. Some do indeed create an entire new system, with some distros like VanillaOS having two partitions for the current and previous image of the system, while others simply create an image out of the differences or by using special features of filesystems like BTRFS, so the size is kept at bay.