Can't boot installed new kernel

[raysa]

I have installed kernel 5.15, and the system now has 5.15, 5.10 and 5.4 all listed as installed, but when I boot, the grub menu (even after going to ‘advanced options’) only offers me 5.4. How can I boot into the latest installed kernel?

[Aragorn]

You haven’t provided us with any information about your system, but a common reason why this sort of thing happens is that you have more than one Manjaro installation on your computer, and that the one in which you installed the additional kernels is not the one whose GRUB you’re using.

There was a similar thread about this subject only a few days ago…

Kernel 5.16.2-1 installed but not running

Currently running Manjaro KDE Qonos 21.2.2 with kernel 5.15.16-1. Decided to install the latest kernel 5.16.2-1. After rebooting the PC, Manjaro Settings Manager shows that kernel 5.16.2-1 is installed but not running. Why? Thanks to savvy members for helping solve this issue.

[raysa]

Thank you. Yes, you’re right. The internal ssd on this laptop went faulty a long time ago and I installed a new system on an inserted microsd which boots on start-up. Somehow the later kernels have ended up in the faulty internal ssd which I can’t use.
I think the other thread you linked to should help me, but I’m rather out of my depth on this, so I’ll pop back if I can’t sort it. Thanks again.

[raysa]

Well, I said I was out of my depth … tried stuff from that thread but no change. How can I get the later kernel installed on the microsd system, and get the computer to ignore the broken internal ssd?
Here’s what lsblk produces:

    ~  sudo lsblk                                                       ✔ 
[sudo] password for ray: 
NAME         MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
mmcblk0      179:0    0  29.1G  0 disk 
├─mmcblk0p1  179:1    0   512M  0 part 
└─mmcblk0p2  179:2    0  26.4G  0 part 
mmcblk0boot0 179:8    0     4M  1 disk 
mmcblk0boot1 179:16   0     4M  1 disk 
mmcblk1      179:24   0 116.5G  0 disk 
├─mmcblk1p1  179:25   0   512M  0 part 
└─mmcblk1p2  179:26   0   116G  0 part /
    ~ 

Thanks.

[Aragorn]

@raysa

How can I get the later kernel installed on the microsd system, and get the computer to ignore the broken internal ssd?

The thing is that you are probably booting from the microSD, but that it’s mounting the root filesystem on the SSD. This is usually due to the wrong UUID being set in GRUB and in /etc/fstab.

So, you would need to get the correct UUID of the root filesystem on the microSD and then modify both the /etc/fstab as well as the /boot/grub/grub.cfg on the microSD to point at that UUID.