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johnklug
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Joined: 17 Jun 2013
Posts: 31

PostPosted: Fri May 13, 2016 5:11 am    Post subject: UEFI/grub2 boot prompts for root device Reply with quote

I tried to follow the Gentoo handbook, and used parted, GPT and put root in the 4th partition.

So when I boot the new system, I am prompted (taken from the screen):
    Determining root device
    Could not find the root device in 231c1cb6-a4e3-494d-97cc-7837d8452dd2.
    Please specify another value or:
    Please press Enter for the same
    Or type "Shell" for shell
    Or type "q" to skip

If I hit enter, then it mounts root and boots.

Here is blkid output:
    /dev/sdb4: UUID="231c1cb6-a4e3-494d-97cc-7837d8452dd2" TYPE="ext3" PARTLABEL="rootfs" PARTUUID="7d95de0c-5b61-4d91-ab9b-199b84f1e5f7"


This is some of what is in grub:
    submenu 'Advanced options for Gentoo GNU/Linux' $menuentry_id_option 'gnulinux-advanced-231c1cb6-a4e3-494d-97cc-7837d8452dd2' {
    menuentry 'Gentoo GNU/Linux, with Linux 4.4.6-gentoo' --class gentoo --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-4.4.6-gentoo-advanced-231c1cb6-a4e3-494d-97cc-7837d8452dd2' {
    load_video
    if [ "x$grub_platform" = xefi ]; then
    set gfxpayload=keep
    fi
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd1,gpt2'
    if [ x$feature_platform_search_hint = xy ]; then
    search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt2 --hint-efi=hd1,gpt2 --hint-baremetal=ahci1,gpt2 5215-084B
    else
    search --no-floppy --fs-uuid --set=root 5215-084B
    fi
    echo 'Loading Linux 4.4.6-gentoo ...'
    linux /vmlinuz-4.4.6-gentoo root=UUID=231c1cb6-a4e3-494d-97cc-7837d8452dd2 ro


The uuid also appears in /dev/disk/by-uuid after booting. The uuid value was entered by grub2-mkconfig from here:
https://wiki.gentoo.org/wiki/Handbook:AMD64/Installation/Bootloader

Root is ext3, and ext3 is selected in the kernel and root mounts fine. From /proc/mounts:
    /dev/sdb4 / ext3 rw,noatime,data=ordered 0 0


So what is missing?
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DONAHUE
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Joined: 09 Dec 2006
Posts: 7550
Location: Goose Creek SC

PostPosted: Fri May 13, 2016 11:29 am    Post subject: Reply with quote

Do a manual edit on /boot/grub/grub.cfg to change to linux /vmlinuz-4.4.6-gentoo root=PARTUUID=7d95de0c-5b61-4d91-ab9b-199b84f1e5f7 ro see if it works (check for typos)
UUID=231c1cb6-a4e3-494d-97cc-7837d8452dd2 points to file system not partition
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johnklug
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Joined: 17 Jun 2013
Posts: 31

PostPosted: Fri May 13, 2016 3:23 pm    Post subject: Reply with quote

Looks like using PARTUUID does not work. I think I need to know how the code evaluates a root disk. I assume this is coming from grub2?

In the new response (slightly changed), hitting enter no longer works. I have to give it a device name:
    Determining root device
    Block device PARTUUID=7d95de0c-5b61-4d91-ab9b-199b84f1e5f7 is not a valid root device ...
    Could not find the root device in .
    Please specify another value or:
    Please press Enter for the same
    Or type "Shell" for shell
    Or type "q" to skip

Enter then did not work. /dev/sdb4 worked. Here are the relevent grub lines compared to blkid output:
    localhost grub # blkid /dev/sdb4
    /dev/sdb4: UUID="231c1cb6-a4e3-494d-97cc-7837d8452dd2" TYPE="ext3" PARTLABEL="rootfs" PARTUUID="7d95de0c-5b61-4d91-ab9b-199b84f1e5f7"
    localhost grub # grep 7d95de0c-5b61-4d91-ab9b-199b84f1e5f7 grub.cfg
    linux /vmlinuz-4.4.6-gentoo root=PARTUUID=7d95de0c-5b61-4d91-ab9b-199b84f1e5f7 ro rootfstype=ext3
    linux /vmlinuz-4.4.6-gentoo root=PARTUUID=7d95de0c-5b61-4d91-ab9b-199b84f1e5f7 ro rootfstype=ext3
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johnklug
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Joined: 17 Jun 2013
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PostPosted: Fri May 13, 2016 9:32 pm    Post subject: Reply with quote

Found the issue. The problem is the genkernel file called init, that winds up in the initramfs file.

On my system, the disks are not ready when the disk queries are made in the init script.

I fixed it by putting busybox sleep 5 in the script called init in initrd.

Seems like this code needs to be written in a loop. It should not give up so soon.

I guess I will write a patch, and then a bug report.
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johnklug
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PostPosted: Sat May 14, 2016 3:36 am    Post subject: Reply with quote

This problem is documented in genkernel bug https://bugs.gentoo.org/show_bug.cgi?id=232733 (not started by me).

I wrote a patch for /usr/share/genkernel/defaults/linuxrc and put it in the bug report, but it is a simple minded loop for 3 seconds waiting for root. Something like this is already done for CD.
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