Persisting a Default Kernel with systemd-boot

I use systemd-boot instead of Grub. It's pretty barebones, which I like. It simply presents a boot menu and then gets out of the way. Like other boot managers, it allows you to set the default boot entry. I just need to set the default= key in /efi/loader/loader.conf to reference one of the .conf files in /efi/loader/entries/ (e.g., 00000000000000000000000000000000-6.14.6-arch1-1.conf). This setup works well. However, in a rolling-release distro like Arch, where kernel packages are frequently updated, there's an issue to address.

Arch provides two kernel packages: linux, which tracks the latest stable kernel, and linux-lts, which tracks the latest LTS kernel version. Having the LTS kernel installed simultaneously gives me a handy fallback if a new mainline kernel makes it so I can't boot. The problem arises when updating linux or linux-lts packages. The .conf filenames change, invalidating the default= value. Ideally, I could make the default entry track either the mainline or LTS kernels regardless of explicit version.

Well, I can! The default= field accepts patterns. So, instead of 00000000000000000000000000000000-6.14.6-arch1-1.conf, you can use 00000000000000000000000000000000-*-arch?-?.conf and, boom, you're always on the latest stable version.

You may be wondering what the field 00000000000000000000000000000000 represents - that's your machine ID. It's a 32-character hexadecimal ID. You can see yours via cat /etc/machine-id.