Sstrhsrtj

I just encountered a weird problem with my system. When I try to boot CentOS 6.9 I get a black screen from the beginning. I can not see the Grub bootloader or anything after selecting the disk to boot from in the BIOS/EFI.

I think I have to give some more insight on this. I have a desktop system with three SSDs. I configured everything so that I was able to install CentOS 7.5 on one SSD, Windows 10 on the other and CentOS 6.9 on the last one. It was a pain in the a** to do this as I had to figure out that I needed to disable all BIOS functionality on the Mainboard and use EFI instead so that all OSs would isntall in EFI-mode. I then used the Grub 2 Bootloader as my "main" booting source and added the entrys for Windows 10 and CentOS 6.9. After much struggle with CentOS I found out that Grub2 is not able to boot CentOS 6.9 directly so I configured a chainloading to the bootloader that was installed with CentOS 6.9. After doing all this, everything worked fine for weeks.

This is my boot entry for CentOS6.9 in Grub2 of Centos7.5:

Insmod ntfs

Insmod chain

Insmod part_gpt

Set root=(hd3,1)

Chainloader /EFI/redhat/grub.efi

And this is the boot entry in the grub of CentOS6.9 that gets chainloaded:

# grub.conf generated by anaconda

#

# Note that you do not have to rerun grub after making changes to this file

# NOTICE:  You have a /boot partition.  This means that

#          all kernel and initrd paths are relative to /boot/, eg.

#          root (hd0,1)

#          kernel /vmlinuz-version ro root=/dev/mapper/vg_centos6-lv_root

#          initrd /initrd-[generic-]version.img

#boot=/dev/sdc1

device (hd3) Linux      HD(1,800,64000,83afa265-4819-4822-bfaa-e6bbe2eff70c)

default=0

timeout=5

splashimage=(hd3,1)/grub/splash.xpm.gz

hiddenmenu

title CentOS 6 (2.6.32-696.el6.x86_64)

        root (hd3,1)

        kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=/dev/mapper/vg_centos6-lv_root nomodeset rd_NO_LUKS LANG=en_US.UTF-8 rd_LVM_LV=vg_centos6/lv_swap rd_LVM_LV=cl/$

        initrd /initramfs-2.6.32-696.el6.x86_64.img

But two days ago I wanted to boot CentOS 6.9 again (Was using Windows 10 and CentOS 7.5 mostly) And after I selected the entry for 6.9 in the boot menu, It said it could not find the hd3,1 partition. I checked with ls on the grub console what partitions are availiable and got the following:

no hd3... . I then selected the ssd with centos6.9 installed to go around the chainloading and got the already mentioned black screen. After that I tried to edit the boot entry in Grub2 of Centos 7.5 to hd2,1 as it looks for me like the numbering just got shifted from 3 to 2. Then I get the same black screen. However, when booting into CentOS 7.5 and mounting sdc1, sdc2 and sdc3 all my files form the CentOS 6.9 including the /EFI/redhat/grub.efi and grub.conf are present.

I dont know of anything I changed on the hardware side or grub configuration since the last time I could boot from 6.9. Does anyone have a suggestion how I could continue troubleshooting?

Greetings,

Mango

EDIT:

Ok, I figured out how to "fix" it but I have no idea what caused my issue. My intention that the drive numbers changed were right and I just overlooked one line where I had to change the drive number. After changing every occurence of hd3 to hd2 it works again.

PS: I think I had a thumb drive attached to the device in the past which is now detached. Could that be an issue? that the thumbdrive was recognized as hd2 for so long and now that it is removed hd3 became hd2?

#boot=/dev/sdc1

device (hd2) Linux      HD(1,800,64000,83afa265-4819-4822-bfaa-e6bbe2eff70c)

default=0

timeout=5

splashimage=(hd2,1)/grub/splash.xpm.gz

hiddenmenu

title CentOS 6 (2.6.32-696.el6.x86_64)

        root (hd2,1)

        kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=/dev/mapper/vg_centos6-lv_root nomodeset rd_NO_LUKS LANG=en_US.UTF-8 rd_LVM_LV=vg_centos6/lv_swap rd_LVM_LV=cl/$

        initrd /initramfs-2.6.32-696.el6.x86_64.img