I have a guest machines (let's call it AutoInstall) running CentOS, running off a Proxmox VE. Other guest machines on that same proxmox VE are not having any issue booting up. Except this Autoinstall machine.

When I click on the noVNC console, I can see Autoinstall is trying to boot up. It says 'Booting from harddisk', then 'Cannot find bootable device', and then it repeat itself non stop.

So I managed to boot Autoinstall up using CDROM, and found there's /dev/sda, /dev/sdb and /dev/sdb1.

But I am not sure which device is the boot up device.

When I do a 'fdisk -l", I see
/dev/sda does not have any partition.
/dev/sdb1 having "Disktype label:dos"

From Proxmox GUI, under Options, I can see Sata0, Sata1, and CDROM as bootup option.

So I choose Sata0 and reboot. In the console, I see "No MBR magic. Warning: treating disk as raw. Booting....". and no further response.

When I choose Sata1 and reboot, In the console I see "Booting..." and no further response.

Question: How do I find out which disk is actually the root partition/disk? IF it's corrupted, how can I restore back, but I do not have any backup/snapshot. Will I loose the data after setup from scratch the CentOS? Thanks for any advice.

You indicate you have 2 devices and you have tried booting from both with no success so you have your answer, neither. When you ran fdisk, did it show a filesystem on sda, should be under the Type column. If you run parted -l as root, it should tell you the filesystem type if one exists. Have you been using this system for some time? Is it new, did it ever boot successfully? Disklabel is for the device not the partition and if yours shows 'dos' then it is likely a Legacy/MBR install. With a Legacy install, boot code is inserted into the MBR and a message you posted would seem to indicate that did not happen.

If you can boot with the cdrom, try mounting the filesystems on each device to explore them to see what if anyting, is one them. Particular interest to any /boot directory information. Is their an EFI partition on either? Is there a BIOS_boot partition?

I think the best starting point for help is to indicate whether this system ever booted. If it did, some change had to be made. If not, the bootloader was likely not correctly installed.

Thanks Yancek. This machine was running fine last time. I just took over this job recently.

After booting up from rescue CDROM, I am not able to mount /dev/sda. It says "NTFS signature is missing, Fail to mount /dev/sta"
For mounting /dev/sdb1, it was mounted. And I do see the folders that contained the our data.

So I guess the /dev/sta (which I believe is Sata0) is indeed setup last time as the bootdisk? But I am puzzled why there's no partition when I do a "lsblk"


sda 8G Disk
sdb 16G Disk
|__sdb1 8G Part