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Old 10-18-2019, 06:12 AM   #1
N6rV1UUV
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CentOS7 fails boot to grub2 after conversion


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
 
Old 10-19-2019, 01:51 AM   #2
syg00
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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.
 
Old 10-22-2019, 07:39 AM   #3
N6rV1UUV
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Quote:
Originally Posted by syg00 View Post
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
 
Old 10-22-2019, 08:08 AM   #4
Firerat
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what happens if you boot with supergrub2
and reinstall grub and regenerate grub.conf ?
 
Old 10-22-2019, 08:44 AM   #5
N6rV1UUV
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Quote:
Originally Posted by Firerat View Post
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.

Last edited by N6rV1UUV; 10-22-2019 at 09:13 AM.
 
Old 10-22-2019, 11:45 AM   #6
Firerat
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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
 
1 members found this post helpful.
Old 10-22-2019, 11:51 AM   #7
jsbjsb001
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Quote:
Originally Posted by Firerat View Post
man grub-install

or possibly man grub2-install

I don't have a centOS to hand
...
Either will work in CentOS.
 
Old 10-22-2019, 11:53 AM   #8
colorpurple21859
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at the grub memu highlight the centos entry, press e for edit, post what is on the line that starts with Linux.
 
Old 10-23-2019, 01:40 AM   #9
N6rV1UUV
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Code:
grub2-install /dev/sda
fixed the problem
 
  


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