The Growing Pains of Linux Boot

In a decisive move just before Fedora 43's final freeze, the Fedora Engineering Steering Council (FESCo) approved an emergency change: doubling the default size of the /boot partition from 1GB to 2GB for new installations. This urgent measure addresses a looming crisis—initramfs images have swelled dramatically, driven by ballooning firmware sizes and configuration shifts in Fedora’s dracut tool. While new installs gain breathing room, users upgrading from Fedora 42 face a stark choice: manually manage /boot space or reinstall entirely.

Anatomy of the Bloat

The tipping point came in early September when developers noticed initramfs sizes had surged from ~35MB to nearly 60MB. Testing failures followed as /boot partitions hit capacity warnings. Investigation traced part of the spike to dracut version 107, which expanded driver/module inclusion to ensure rescue images remained portable across hardware (e.g., after an NVMe drive migration). This well-intentioned change was partially rolled back after being flagged as a release-blocking bug.

But firmware proved a harder problem. By late September, rescue initramfs images weighed in at over 256MB with NVIDIA and AMD firmware—NVIDIA alone consumed 99MB. Fedora last resized /boot in 2016 (512MB→1GB), but firmware now grows "at a faster rate than most other things," noted developer Chris Murphy. With kernels, initramfs files, and rescue images competing for space, the 1GB ceiling became unsustainable.

Alternatives Debated and Dismissed

Proposals to mitigate the crisis sparked vigorous debate:

  • Btrfs Subvolumes: Using a Btrfs subvolume for /boot would eliminate fixed-size constraints by sharing pool storage. However, GRUB lacks upstream support for this—a SUSE-patched version exists but isn’t battle-tested for Fedora 43.
  • Dropping Rescue Images: Some argued rescue kernels are rarely used, suggesting live USBs suffice. Critics countered that live images require expertise and external media: "Only experts can do this... We have to accept this, or we will never be 'the next coming pc desktop os,'" asserted developer Marius Schwarz. The idea gained little traction.

The 2GB Compromise

Despite optimizations—like trimming redundant NVIDIA firmware versions—the 1GB limit remained untenable. FESCo fast-tracked the partition increase, acknowledging the firmware problem is universal (affecting ARM and x86 alike). While late-cycle changes carry risk, the council prioritized long-term usability. As Neal Gompa emphasized: "The firmware problem isn’t x86-specific. It’s way more visible on x86, but it’s not an x86-only problem."

What This Means for Users

  • New Installs: Fedora 43’s Anaconda installer and image-builder will allocate 2GB to /boot, accommodating growth for years.
  • Existing Systems: Upgraders receive no automatic relief. Fedora’s documentation bluntly advises considering "reinstalling instead of upgrading." Workarounds include:
    • Reducing retained kernels (set installonly_limit=2 in /etc/dnf/dnf.conf).
    • Manually removing the rescue image (disable via dracut_rescue_image="no" in /usr/lib/dracut/dracut.conf.d/02-rescue.conf).

The change underscores a broader industry challenge: firmware’s relentless expansion. As hardware complexity grows, Linux distributions must balance robustness, user experience, and practical constraints—a tension unlikely to fade soon. Fedora’s reactive fix is a stopgap; sustainable solutions may require rethinking initramfs architecture or firmware packaging itself.

Source: LWN.net - Sudden increases in the size of Fedora's initramfs