Fail to use UUID in grub2

ROHK · 10-02-2016, 06:39 AM

hi all,
I encounter a problem in booting into the system using grub2.

I have two partitions
/dev/sdc14 is /mnt/lfs/boot
/dev/sdc15 is /mnt/lfs

I have two version of grub menu entries

Code:

menuentry "GNU/Linux, Linux 4.7.2-lfs-7.10-systemd" {
        insmod part_gpt
        insmod ext2
        # set root=(hd0,gpt14)
        search --fs-uuid --no-floppy --set-root f215d53a-89e3-4b7b-99fc-77ab8feceb9c
        # system root=/dev/sdc15
        linux   /vmlinuz-4.7.2-lfs-7.10-systemd root=UUID=1b68e291-5e15-484a-a0ab-36acff02f95b ro
}

version 2

Code:

menuentry "GNU/Linux, Linux 4.7.2-lfs-7.10-systemd" {
        insmod part_gpt
        insmod ext2
        set root=(hd0,gpt14)
        linux   /vmlinuz-4.7.2-lfs-7.10-systemd root=/dev/sdc15 ro
}

version 2 will boot without error. However, the version 1 fails to boot
https://drive.google.com/file/d/0B8v...ew?usp=sharing

Can someone tell me what's wrong with the version 1.

stoat · 10-02-2016, 10:05 PM

Try creating an initial ram filesystem. It's a BLFS topic but easy, harmless, and reversible...

http://www.linuxfromscratch.org/blfs...initramfs.html

When you've done that, also add insmod search_fs_uuid and an initrd line to the grub.cfg commands.

P.S.: It may not apply in your case, but when using UUID or LABEL because the system is located on a hot-pluggable drive (a good idea), the rootdelay=5 kernel parameter is usually required to mitigate the slower response of an external drive. Anyway, I use 5 (seconds). Some people say 10. Experiment with that to find the shortest delay that works.

P.P.S.: That ext2 module is a default module. You can omit its insmod command if you like.

ROHK · 10-03-2016, 09:17 AM

Many~~Many thanks for your detailed explanation! I just finished the LFS and entering into the BLFS.

syg00 · 10-03-2016, 06:20 PM

Note that an initrd is not required - as you are using gpt, you can pass PARTUUID. Not much different to /dev nodes in the grand scheme of things.
Personally I feel UUID has as many drawbacks as advantages in this case.