bcachefs on RHEL 10.2: The Kernel That Said No

A while back I put RHEL on a ZFS root, declared it cursed, and the homelab VM lived to tell the tale. That one worked, which is the dangerous kind of outcome, because it teaches you the wrong lesson. The wrong lesson is “the kernel does not care what filesystem holds root, so anything is possible if you disable enough checks.” This is the sequel where the kernel reminds me that it absolutely does care, thank you very much, and that “anything is possible” has an asterisk the size of a merge window. This time the target was bcachefs. The plan was simple: get bcachefs running on a fresh RHEL 10 box, write a smug little post about subvolumes and snapshots, go to bed. What I got instead was a four hour speedrun through every layer of the out-of-tree kernel module experience, a defeat so total I had to switch distributions, and this post, which is less “how to” and more “post-mortem.” Let me be clear from the top, in the grand tradition of these articles: this was a bad idea. Not “edgy…