access to grub menu to boot other kernels

[faramirza]

I accidentally changed my boot order to boot into memtester by default. When the Proxmox host boots up I press shift but I do not get the menu to change to the proper kernels. Is proxmox not using Shift like ubuntu to access grub boot menu? I briefly see the word grub followed by memtester when booting my host.

 

[Stoiko Ivanov]

Usually the grub screen (blue+green) stays on for 5 seconds (GRUB_TIMEOUT setting in /etc/default/grub) - so you should have plenty of time to hit the up arrow

if something changed there - you can always boot with a live ISO, mount your system disk (and /proc, /sys and the like) - chroot into it and fix the grub configuration

I hope this helps!

 

[faramirza]

I wanted to boot an older kernel which I find easy to do on Centos but I keep on breaking my grub config on Debian/Proxmox. In the following example what number is my default kernel if I want to boot the older 5.13 version? I set my default kernel value (GRUB_DEFAULT=0) to 3 or for that matter any value it seems followed by running update-grub and I end up in memtest.

→ grep menuentry /boot/grub/grub.cfg
if [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
  menuentry_id_option=""
export menuentry_id_option
menuentry 'Proxmox VE GNU/Linux' --class proxmox --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
submenu 'Advanced options for Proxmox VE GNU/Linux' $menuentry_id_option 'gnulinux-advanced-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
    menuentry 'Proxmox VE GNU/Linux, with Linux 5.15.35-1-pve' --class proxmox --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.15.35-1-pve-advanced-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
    menuentry 'Proxmox VE GNU/Linux, with Linux 5.15.35-1-pve (recovery mode)' --class proxmox --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.15.35-1-pve-recovery-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
    menuentry 'Proxmox VE GNU/Linux, with Linux 5.13.19-6-pve' --class proxmox --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.13.19-6-pve-advanced-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
    menuentry 'Proxmox VE GNU/Linux, with Linux 5.13.19-6-pve (recovery mode)' --class proxmox --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-5.13.19-6-pve-recovery-4c7cebce-e0d2-4ba1-ab58-6e0cdbe49988' {
menuentry "Memory test (memtest86+)" {
menuentry "Memory test (memtest86+, serial console 115200)" {
menuentry "Memory test (memtest86+, experimental multiboot)" {
menuentry "Memory test (memtest86+, serial console 115200, experimental multiboot)" {

 

[Stoiko Ivanov]

I wanted to boot an older kernel which I find easy to do on Centos but I keep on breaking my grub config on Debian/Proxmox. In the following example what number is my default kernel if I want to boot the older 5.13 version? I set my default kernel value (GRUB_DEFAULT=0) to 3 or for that matter any value

a) with pve 7.2 we included kernel pinning - running `proxmox-boot-tool kernel pin 5.13.19-6-pve` should get everything setup correctly
b) what's the issue that makes you want to go to an older kernel (while this can help temporarily - keep in mind that Proxmox will only update the 5.15 kernels from now on - so to get coverage of security fixes it really would be good to fix issues with the 5.15. kernel
c) as for the grub default selection with submenus - I agree it's a bit ... odd you need to set the 'path' separated by '>' so something like '1>3' could work for your case (untested) - see https://www.gnu.org/software/grub/manual/grub/html_node/default.html

I hope this helps!

 

[faramirza]

a) with pve 7.2 we included kernel pinning - running `proxmox-boot-tool kernel pin 5.13.19-6-pve` should get everything setup correctly
b) what's the issue that makes you want to go to an older kernel (while this can help temporarily - keep in mind that Proxmox will only update the 5.15 kernels from now on - so to get coverage of security fixes it really would be good to fix issues with the 5.15. kernel
c) as for the grub default selection with submenus - I agree it's a bit ... odd you need to set the 'path' separated by '>' so something like '1>3' could work for your case (untested) - see https://www.gnu.org/software/grub/manual/grub/html_node/default.html

I hope this helps!

I use Carbon Black which seems to be incompatible with 5.15 at this time. So I want to ensure I boot with 5.13 kernel as my default when Carbon Black used to work with. I'm sorry. I don't follow your explanation on point c. Is the first 1 the first main entry followed by the 3 as the subentry?

 

[newuser123]

Usually the grub screen (blue+green) stays on for 5 seconds (GRUB_TIMEOUT setting in /etc/default/grub) - so you should have plenty of time to hit the up arrow

if something changed there - you can always boot with a live ISO, mount your system disk (and /proc, /sys and the like) - chroot into it and fix the grub configuration

I hope this helps!

Hello brother - can you please point me to resources on how to do this in detail? I'm clear on booting using the live ISO, but unclear on the next steps. Appreciate it greatly (coming from an entire weekend of configuring my beautiful proxmox server, to it not booting all of sudden and scrambling to get it back up)