Misc. Improvements Draft PR by antheas · Pull Request #2294 · bootc-dev/bootc · GitHub

Here are some improvements I came up with while working with bootc lately. They are by no means ready to merge (and vibed). Hopefully they are an inspiration.

Here is a small summary.

The current RPM for bootc compiles bootc three times because of the docs and tests instead of re-using the first build. Commit is junk and I vibed it, but I need to be able to build the spec for my workflow. It would be nice to fix so it compiles once.
bootc internals ostree-ext container encapsulate --contentmeta still adds the empty package layer. It probably shouldn't. The caller can add an extra layer if they desire. I am unaware of someone using the previous manifest option with rpm-ostree in either case.
bootc internals ostree-ext container encapsulate and ABI is still single threaded, and because of the current architecture it's very hard to fix (by hand). But it is around 3 times faster with 4 workers (~3min to 40s in testing)
Bootc does not preserve the .version key during merge commits so ostree does not write the version on the bootloader. Perhaps the source here should be the OCI label, but for my usecase the ostree tag works fine.
bootc internals ostree-ext container unencapsulate always does a checkout, even when a commit has no derived layers. This adds 10-20 seconds on deployment times universally and spins fans, even though it is not needed. It is also important for my usecase because it means you cannot do unencapsulate on a bare-split-attrs repo currently, because it does not support checkouts.

Thanks for submitting this, I think it'd make sense to split this into distinct PRs?

This completely breaks the buildsystem, no? We'd just silently be reusing old binaries...

yes, that patch is not good and not designed for merge. But it did its job for me.

It is very hard to iterate with bootc while having it compile three times to deploy

But yes, this is really really messy how we have our documentation depend on running the binary.

Maybe what is easier is to try to move instead to where we just validate the generated docs as a separate phase, but don't default to linking the two together.

It's effectively what we did for the tmt stuff

I think it'd be cleaner to use https://doc.rust-lang.org/stable/std/thread/fn.scope.html - or use rayon. (Or use tokio)

Yeah, this was a fast fixup that works. I wouldn't be happy merging it, the deploy speedup is real though

I agree we never used this in practice, and we can probably drop it now. OTOH, this code is basically obsoleted by https://github.com/coreos/chunkah anyways?

that is a nice tool. I will keep it in mind for non-ostree images

ostree-ext provides a fast deploy path for ostree backends so it will have to stay around until the composefs backend is stable with similar performance to the fast ostree deploy path, then add 2-3 more years for migration or a way to specify to bootc interim migration paths so e.g., version 2027.3 switches to composefs and points ostree instances to 2027.2 that has the machinery to migrate from ostree to composefs while being built for ostree. Ah.

This may relate to #2136

Related but not quite. It's true that for images built with docker / buildah they need to be tagged twice so docker compatible registries that only read the leaf manifest can see the tag and tools like podman / skopeo that read the inner config can pick up those

This fixes the bootloader version exposed by ostree. Without this entries appear like PRETTY_NAME. This PR supersedes the one for PRETTY_BOOTLOADER

Ideally on the spinoff, bootc could be taught to set the version tag on the merge commit based on org.opencontainers.image.version while falling back to ostree

Hi, yes, this PR is not designed to merge

It is more of an issue with some draft solutions attached, moreso for inspiration.

Which ones do you think should spinoff as draft PRs and which should land in an issue?

By the way, I had another look at chunkah and dmnks/rpm@1825517

Great work on landing --parkdb! I cannot wait to try it out.

I went through my image and fixed some layer invalidations, specifically the initramfs plus some libdnf weirdness.

For chunkah, you need to make sure /usr/lib/sysimage/libdnf5/ is unpackaged, because it is owned by libdnf5 and it will corrupt its layer when packages change. /etc/os-release should also be unpackaged (owned by fedora-release). bootupd is also a bit naughty and timestamps EFI.json (/usr/lib/bootupd/updates/EFI.json needs to be unpackaged) Then, dropping these three files is sound:

    /usr/lib/sysimage/libdnf5/transaction_history.sqlite
    /usr/lib/sysimage/libdnf5/transaction_history.sqlite-shm
    /usr/lib/sysimage/libdnf5/transaction_history.sqlite-wal

They are ghost files with timestamps, although I am unsure of the implication of removing them.

For the initramfs, it includes os-release so some care needs to be taken for the image version to be added after the initramfs is built. There is also a sysusers dracut bug, where when it adds dbus it adds a modification day since epoch to /etc/shadow (we should probably open an issue for that). This causes the initramfs to change every day. But with those fixed, assuming no packages that touch the initramfs such as kernel and firmware are the same, the initramfs is the same! So, the layer stays the same and soft reboot works!

With those improvements, if I rebuild the image from scratch, only the commit layer and unpackaged layer change, with a total of ~80mb, and bootc from this PR deploys the image in ~10 seconds. It is so fast that I cannot measure it.

You need to keep that in mind before deprecating the rpm-ostree rechunker (which I do not use) or bootc internals ostree-ext (which I do use), as chunkah does not have the fast deploy path

EDIT: Deployment takes 13 seconds, diff is 59mb

antheas added 5 commits July 8, 2026 02:37

bootc compiles three times for specs, make it compile once

b950604

Drop reserved package layer

b08e289

add parallel writer

b49c268

Preserve image version in merge commits

dfad00c

Optimize pure OSTree image imports

69807fe

github-actions Bot added the area/ostree Issues related to ostree label Jul 8, 2026

bootc-bot Bot requested a review from gursewak1997 July 8, 2026 00:55

cgwalters requested changes Jul 9, 2026

View reviewed changes

               .PHONY: bin
               bin: manpages
-              	cargo build --release --features "$(CARGO_FEATURES)" --bins
+              	if [ ! -x "$(BOOTC_TARGET_DIR)/bootc" ]; then \

               .PHONY: manpages
               manpages:
-              	cargo run --release --package xtask -- manpages
+              	if [ -x "$(BOOTC_TARGET_DIR)/bootc" ]; then \

+                      let commit = commit.to_string();
+                      let ocidir = ociw.dir().try_clone().context("Cloning OCI directory")?;
+                      let opts = worker_opts.clone();
+                      handles.push(thread::spawn(move || {

                           META_CONFIG,
                           import.config.to_canon_json_string()?.to_variant(),
                       );
+                      if let Some(version) = image_version {

Misc. Improvements Draft PR by antheas · Pull Request #2294 · bootc-dev/bootc · GitHub

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                       r.push(max_freq_components);
                   }
-                  // Allocate an empty bin for new packages

Misc. Improvements Draft PR by antheas · Pull Request #2294 · bootc-dev/bootc · GitHub

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