On Fri, Jul 19, 2019 at 12:37 PM Ian Zimmerman <i...@very.loosely.org> wrote: > > On 2019-07-19 20:58, Adam Carter wrote: > > > I experimented found the following worked in /etc/default/grub; > > > > GRUB_DEVICE="PARTUUID=d3554d49-02" > > > > Which writes grub.cfg as; > > linux /vmlinuz-5.2.0-gentoo root=PARTUUID=d3554d49-02 ro > > init=/usr/lib/systemd/systemd iommu=pt raid=noautodetect > > > > PARTUUID looked up with blkid. No initramfs required :) > > I don't get this. blkid is userspace. The _kernel_ needs to know what > the root fs device is, before it even starts pid 1.
The kernel init code is able to find a device given its PARTUUID. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/init/do_mounts.c?h=v4.19.59#n172
