[SOLVED] CentOS7 fails boot to grub2 after conversion

N6rV1UUV · 10-18-2019, 05:12 AM

I converted centos7 phisical machine with one HDD to vmware VM and process separated boot partition to another virtual disk. So boot fails in grub2 console, I have been able to boot OS normally with mounted supergrub2.iso but I want to fix bootloader.

Code:

grub> ls
(hd0) (hd0,msdos1) (hd1) (hd1,msdos1) (lvm/centos-swap) (lvm/centos-home) (lvm/centos-root)

(hd0,msdos1) is boot partition.

Code:

grub> set
...
prefix=(lvmid/*some garbage*)/boot/grub2
...
root=(lvmid/*some garbage*)

I tried

Code:

set root=(lvm/centos-root)
linux (hd0,msdos1)/vmlinuz...
initrd (hd0,msdos1)/initrd...
boot

which fails to start Switch Root

syg00 · 10-19-2019, 12:51 AM

If you created a non-LVM boot partition on (hd0,msdos1) the grub variables need to be set to that - notably both prefix and root.

N6rV1UUV · 10-22-2019, 06:39 AM

Quote:

Originally Posted by syg00

If you created a non-LVM boot partition on (hd0,msdos1) the grub variables need to be set to that - notably both prefix and root.

I tried:

Code:

set root=(lvm/centos-root)
set prefix=(hd0,msdos1)/grub2
linux (hd0,msdos1)/vmlinuz...
initrd (hd0,msdos1)/initrfs...
boot

Which starts boot process but fails starting initrd-switch-root.service with following error:

Code:

Failed to switch root: Specified switch root path /sysroot does not seem to be an OS tree. os-release file is missing.

This happens with all installed kernel versions

Firerat · 10-22-2019, 07:08 AM

what happens if you boot with supergrub2
and reinstall grub and regenerate grub.conf ?

N6rV1UUV · 10-22-2019, 07:44 AM

Quote:

Originally Posted by Firerat

what happens if you boot with supergrub2
and reinstall grub and regenerate grub.conf ?

There are no option to reinstall grub2.
I have "Super Grub2 Disk 2.04s2-beta2"

EDIT:
sorry I misunderstood you.
I booted with supergrub and tried:

Code:

rm -rf /etc/default/grub
rm -rf /etc/grub.d/*
yum reinstall grub2-tools
grub2-mkconfig -o /boot/grub2/grub.cfg

which had no effect, normal boot still fails the same.

Firerat · 10-22-2019, 10:45 AM

man grub-install

or possibly man grub2-install

I don't have a centOS to hand

Code:

/usr/sbin/grub-install --help
Usage: grub-install [OPTION...] [OPTION] [INSTALL_DEVICE]
Install GRUB on your drive.

      --compress=no|xz|gz|lzo   compress GRUB files [optional]
      --dtb=FILE             embed a specific DTB
  -d, --directory=DIR        use images and modu<snip>

my assumption is that when grub is installed to the device it is "hardcoded" with mapping to the grub.conf

since you created a virtualDisk this mapping is no longer valid
I believe grub-install would fix that

jsbjsb001 · 10-22-2019, 10:51 AM

Quote:

Originally Posted by Firerat

man grub-install

or possibly man grub2-install

I don't have a centOS to hand
...

Either will work in CentOS.

colorpurple21859 · 10-22-2019, 10:53 AM

at the grub memu highlight the centos entry, press e for edit, post what is on the line that starts with Linux.

N6rV1UUV · 10-23-2019, 12:40 AM

Code:

grub2-install /dev/sda

fixed the problem