Jtdylktuy

There is a certain ubuntu image that works (from the SD card) with a hardware controller. The whole image takes 2 gigabytes, for such is the card size. The image is built on the old kernel. We need to replace the motherboard, because old one are no longer available, and new appropriate don't speak with old kernel. And most importantly, irrevocably (due to a certain chaos when changing developers) the root password from the image is lost - that is, replacing the kernel in a civilized manner, from the inside, alas, will not work. The question: is it possible - and how can I- change the kernel, without changing the rest, outside the system, simply by rewriting something the card with existing image from my laptop? If not, it will be necessary to rebuild the entire streamlined and debugged image, which I would like to avoid.

First, I can not stress enough not to use your working copy, but to make a backup copy and use that incase something goes horribly wrong.

This may not work, but its your best shot.

The kernel is dependent on the files in /boot to start with.

System.map-4.19.1-1-default

.vmlinuz-4.19.4-1-default.hmac

config-4.19.4-1-default

initrd-4.19.1-1-default

initrd is symlinked to above

symvers-4.19.1-1-default.gz

sysctl.conf-4.19.1-1-default

vmlinux-4.19.1-1-default.gz

vmlinuz symlink to below

vmlinuz-4.19.4-1-default

You need all of these files in from the new version present, obviously most of the files names contain the version number and will be different depending on the kernel version you are using.

Inside /lib/modules/ is a series of folder one for each kernel version.
For example:

4.19.4-1-default

All the modules in this folder would be needed to be copied over.

Finally your grub or grub2 files will need to be modified to point to this new files.

1. Backup your SD card and use the backup copy


2. If your old motherboard is non UEFI disable it on the new motherboard, or there will be issues.


3. Get another SD card/hdd


4. Install a newer version of whatever distro you were using.


5. Copy /boot and /lib/modules/ to the appropriate places on the backup copy of your OS. If present /usr/lib/bootloader also should be copied over.


6. Boot and see what happens.

There will probably be further compatibility issues. The biggest danger is moving to far forward and transitioning from initd to systemd or other major change.

I would suggest finding out what version of the distro you were using and move only 1 version higher to start with. If installation fails you can move forward one version at a time.

When you have a bootable system, then I suggest using apt-get or etc to do a full distro upgrade in the proper manor.