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c/linux · by user_6282638282@sopuli.xyz · 21d

Have I misunderstood immutable distros?

I have Bazzite running on a BC-250 machine. A few weeks ago, I made some changes using rpm-ostree related to zram and swap. I had assumed that, because I used rpm-ostree, the changes would become part of the "tree" and I could rollback to the original settings. But when I went to look at Bazzite's rollback tools, it seemed solely focused on rolling back to previous official releases, and I couldn't find any reference to the specific changes I made.

40 points · 11 comments · view on lemmy.world

11 Comments

breadsmasher@lemmy.world · 23 pts · 21d (5 replies)

https://docs.bazzite.gg/Installing_and_Managing_Software/rpm-ostree/

Layering packages irresponsibly can be destructiveand may prevent updates as well as other issues until the layered packages are removed.

Use this method as a last resort and for anything at a "system-level" only since it can pause updates, if the package contains dependency issues with future upgrades, until the package is uninstalled.

MAJOR caveats using rpm-ostree

Layering packages can cause severe consequences including:

  • Pause system updates until package(s) are uninstalled.
  • Prevent rebasing to different images until package(s) are uninstalled.
  • Conflict with existing packages as part of the image leading to dependency issues.
  • Updates taking longer to download as you layer more packages to your system.

Youre breaking a core tenant of immutable distros by installing system level packages. i think that might be your misunderstanding?

who@feddit.org · 14 pts · 21d

Youre breaking a core tenant

Did you mean tenet?

user_6282638282@sopuli.xyz · 9 pts · 21d (2 replies)

Seems that way

breadsmasher@lemmy.world · 1 pts · 21d (1 reply)

Its factually that way

zelahdieliekeis@piefed.blahaj.zone · 5 pts · 21d

rude

throwaway403@programming.dev · 7 pts · 21d

Bazzite's messaging has merit, but we'd be making a mistake by regarding it as absolute. It makes more sense to take them as carefully written guide lines for a specific audience.

Furthermore. with all due respect, but OP's writing doesn't imply installing/managing software with rpm-ostree. Which, is actually the subject of the documentation entry you quoted. As such, I think you might have misunderstood them.

Youre breaking a core tenant of immutable distros by installing system level packages.

Finally, FWIW, I absolutely disagree with the above. The page you quoted from seems to agree with me on this: "Layering packages are mostly intended for system-level applications, libraries, and other dependencies."

throwaway403@programming.dev · 11 pts · 21d (2 replies)

I made some changes using rpm-ostree related to zram and swap

Could you be more transparent and/or elaborate in this regard? Like, what did you actually do?

FWIW, I've been on Fedora Atomic since before Bazzite's existence, but I've never once considered using rpm-ostree to make changes to zram and swap. So, I'm a bit confused. To be clear, it's perfectly possible that what you did is 100% legit, but that it just happened to expose a gap in my knowledge.

I had assumed that, because I used rpm-ostree, the changes would become part of the “tree” and I could rollback to the original settings. But when I went to look at Bazzite’s rollback tools, it seemed solely focused on rolling back to previous official releases, and I couldn’t find any reference to the specific changes I made.

Basically, while rpm-ostree does offer git-like control on your base system; hence, why it's so powerful to begin with. It does not keep more than two deployments around; at least, by default.

If you would like to keep around a specific deployment (for whatever reason), you can do so with the ostree admin pin <insert number> command. The git-like control also enables you to keep track of:

  • the changes applied to /etc; invoke ostree admin config-diff to see what files have been added or modified since installation
  • layered packages; simply invoke rpm-ostree status

Keeping track is cool and all, but its usefulness is in full display with powerful applications such as:

  • rpm-ostree reset; this basically removes all permutations. That is, two people on the same image, will have the identical base system after this. (Note that this still isn't as powerful as a factory reset. For that, refer to this issue tracker on bootc^[On that note, bootc's model is arguably better suited if you're just interested in finding back references to changes you made in the past. Granted, bootc offers a hefty amount of freedom in how you'd approach this and might be overwhelming for now. FWIW, both Bazzite and this are products of this.].)

Finally, the git-like structure ensures actual reversibility. On most other systems, installing A -> installing B -> uninstalling A will yield a different state than just installing B. With rpm-ostree, the base system between the two will be identical.

For completeness' sake, I've used "base system" above to just mean the contents of /usr and /etc (and maybe some other subdirectories of /). Crucially, the contents of /var are not part of the "base system".

user_6282638282@sopuli.xyz · 2 pts · 20d (1 reply)

The instructions I followed are in the description of the following video. A lot of what happens with this project is hidden away on Discord servers and I suspect what makes it out to the web has gone through the slop filter.

https://m.youtube.com/watch?v=A6juAoY70aU

The bottom line is that I thought this might help with random crashes I'd been having with a particular emulator. Unfortunately it had the opposite effect and the same emulator now consistently hard-locks the system after this "fix".

throwaway403@programming.dev · 3 pts · 20d

Thank you! This is actually very helpful! And we can definitely reverse some of their doing 😉. Below I will repeat the invoked commands and provide some context/explanation. So, without further ado.

sudo rpm-ostree kargs --append-if-missing=zswap.enabled=1
sudo rpm-ostree kargs --append-if-missing=zswap.max_pool_percent=25
sudo rpm-ostree kargs --append-if-missing=zswap.compressor=lz4
sudo rpm-ostree kargs --append-if-missing=systemd.zram=0

The commands found above were used to change the kernel arguments through rpm-ostree. You can still find these back with rpm-ostree kargs --editor. You can even outright remove them, then and there. It's also possible to literally revert those commands by invoking the following:

sudo rpm-ostree kargs --delete-if-present=zswap.enabled=1
sudo rpm-ostree kargs --delete-if-present=zswap.max_pool_percent=25
sudo rpm-ostree kargs --delete-if-present=zswap.compressor=lz4
sudo rpm-ostree kargs --delete-if-present=systemd.zram=0

sudo rpm-ostree initramfs --enable --arg=--add-drivers --arg=lz4

Unfortunately, I don't have any experience with this.

sudo swapoff -a
sudo rm -rf /var/swap
sudo semanage fcontext -a -t var_t "/var/swap(/.*)?"
sudo restorecon -Rv /var/swap
sudo btrfs filesystem mkswapfile --size 32G /var/swap/swapfile
sudo semanage fcontext -a -t swapfile_t "/var/swap/swapfile"
sudo restorecon -v /var/swap/swapfile
sudo swapon -a

Basically, the commands found literally above affect the contents of /var. As such, they're outside of the 'jurisdiction' of rpm-ostree. Reverting these is the same as on any other Linux system.

The following commands change the contents of /etc. As such, they're being tracked and can be reverted to their original states. Though, I'm not sure if it's possible to revert them back to their respective versions without those changes.

sudo sed -i '\|/var/swap/swapfile|d' /etc/fstab

I'll be honest with ya. I don't know what this one does 😅. I have used sed in the past but wasn't able to decipher this one. FWIW, it tries to make some changes to /etc/fstab . And, if I'd have to make a guess, I think it deletes any lines that contain /var/swap/swapfile.

echo "/var/swap/swapfile none swap defaults,nofail 0 0" | sudo tee -a /etc/fstab

This added some text to /etc/fstab. To revert it, go to /etc/fstab, and remove /var/swap/swapfile none swap defaults,nofail 0 0

echo "vm.swappiness=120" | sudo tee /etc/sysctl.d/99-swappiness.conf

This created a file named 99-swappiness.conf and placed it to /etc/sysctl.d/. As such, a simple sudo rm -rf /etc/sysctl.d/99-swappiness.conf suffices.

sudo rpm-ostree install policycoreutils-python-utils

This was an optional command. If you did have to invoke it, then you should find policycoreutils-python-utils when invoking rpm-ostree status. It should be mentioned as a layered package.

To undo it, simply invoke rpm-ostree uninstall policycoreutils-python-utils.

Eeyore_Syndrome@sh.itjust.works · 9 pts · 21d (1 reply)

There's even a Doc for that:

Using Swap for Additional Memory or Hibernation

user_6282638282@sopuli.xyz · 3 pts · 20d

🤦 thanks for this