After my latest experiment I encountered an issue where the current lack of video output from Proxmox on my N54L-based HP Microserver Gen 7 became a serious issue: I would see the Grub menu, then the screen would turn blank and enter power-save mode, I’d see the disk activity light blink a few times, but the system wouldn’t start up.
Naturally, without seeing the error message I couldn’t do anything about the issue, but I had seen a similar symptom earlier, namely when installing Proxmox for the first time: The installer USB image behaves the same way on this computer, and the workaround there is simply to press Enter to enter the graphical install environment after which the screen is visible.
This time I re-created a Proxmox 5.2 USB stick, booted the server from it, and correctly assumed that arrow down followed by Enter would likely get me into some sort of rescue environment. Sure enough I was soon greeted by a root prompt. At this stage, the ZFS modules weren’t loaded, so again I guessed that pressing Ctrl+D to exit the rescue environment would start the install environment where I know ZFS is available, and pressing the Abort button there luckily got me back to a shell.
From here I mounted my ZFS environment and chrooted into it:
# zpool import -f -a -N -R /mnt # zfs mount rpool/ROOT/pve-1 # zfs mount -a # mount --rbind /dev /mnt/dev # mount --rbind /proc /mnt/proc # mount --rbind /sys /mnt/sys # chroot /mnt /bin/bash --login
I could now confirm that I was within my regular Proxmox file system, and so I got to work on the Grub configuration:
In /etc/default/grub, I found the commented out line #GRUB_GFXMODE=640×480 and changed that portion of the file so it now looks like this:
GRUB_GFXPAYLOAD_LINUX="keep" GRUB_GFXMODE=1024x768 GRUB_CMDLINE_LINUX_DEFAULT="nomodeset"
I then ran update-grub and rebooted the server, after which I could see the boot process including the issue that prevented the system from booting fully: It turns out my ZFS pool didn’t want to mount after replacing the drive. I quickly ran zpool import -f, and exited the shell, and then the system successfully booted the rest of the way. An additional reboot confirmed that the system was functional.
Troubleshooting gets a lot harder when you’re blind. The solution is to attempt to become less blind.