I’m running Debian 12 with kernel 6.9.12-amd64. When grub generates its config file (e.g. via grub-mkconfig), all the Debian entries have systemd.unified_cgroup_hierarchy=false appended in their Linux command. This is not present in /etc/default/grub, where GRUB_CMDLINE_LINUX_DEFAULT="quiet" and GRUB_CMDLINE_LINUX="" (no mention of cgroups appears). So where is this coming from?
This is a problem, because when I boot now, I get a fatal error from systemd saying
Refusing to run under cgroup v1. SYSTEMD_CGROUP_ENABLE_LEGACY_FORCE=1 not specified on kernel command line.
When I add that parameter, it boots, but I get a deprecation message and boot is delayed by 30s.
It seems like Debian is preventing using cgroups v2, but that the latest versions of systemd require it. What should I do here? It seems to me like I should switch to cgroups v2 and find a way to not have grub appending systemd.unified_cgroup_hierarchy=false by default, which is why I’m wondering where that’s coming from. Is there some danger or downside to enabling cgroups v2? (I also manually removed that line and booted with cgroups v2, things seem fine?)