I did an upgrade of 18.04LTS -> 22.04LTS using the software updater. After rebooting the system does not boot proper. Below the output (manual re-entered from the other machine, so maybe a type)

Call Trace:
<TASK>
show_stack+0x52/0x5c
dump_stack_lvl+0x4a/=x63
dump_stack+0x10/0x16
panic+0x149/0x321
mount_block_root+0x144/0x1dd
mount_root0x10c/=x11c
prepare_namespace+0x13f/0x191
kernel_init_freeable+0x18c/0x1b5
? rest_init+0x100/+x100
kernel_init+0x1b/0x150
?rest_init+0x100/0x100
ret_from_fork+0x22/0x30
</TASK>
Kernel Offset: 0x1da00000 from 0xffffffff81000000 (relocation range: 0xffffffff81000000-0xffffffffbfffffff)
---[ end Kernel panic - not syyncing: VFS: Unable to mount root fs on unknown-block(0.0) ]---

I've an (old) Lenovo W540, 8core, 2.7GHz, 32Gb RAM

I tried to salvage with a boot from USB (Linux 22.04 Desktop), but since I did not see the original files I decided against installing

Anyone suggestions? As long as I get my data off it's all fine by me (so using the OS from USB, but with access to the data under )

Thanks,

Andreas

I don't know the steps the OP followed but to anyone trying to update from 18.04 to 22.04 these steps worked for me on two systems (Intel 4790 and Ryzen 2400G):

You need to do a release upgrade from 18.04 to 20.04 and then from 20.04 to 22.04

Step by step:

1. tappend these to /etc/apt/sources.list (this is an important step that fixes the OP question, without this you cannot upgrade packages, and dist-upgrade, and without that you cannot do the releas upgrade):

deb http://archive.ubuntu.com/ubuntu bionic main restricted
deb http://archive.ubuntu.com/ubuntu bionic-updates main restricted
deb http://archive.ubuntu.com/ubuntu bionic-security main restricted

2. Now on the following steps you would be needing to answer with OK and y on a few questions so make sure you look once in a while on your display, you would be needing a few restarts and it takes anywhere from half an hour to 1-2 hours, update the package list:

   sudo apt update

now upgrade packages:

sudo apt upgrade

followed by dist upgrade

sudo apt dist-upgrade

then remove all packages from your system by entering the following command (this is optional):

sudo apt autoremove

install the update-manager-core package by running the following command, in case you don't have it already:

sudo apt install update-manager-core

after that, you cand run the release upgrade utility. To do this by the following command:

sudo do-release-upgrade

after this is ready you have 20.04, once you have 20.04 (check with lsb_release -a) run one more time:

sudo do-release-upgrade

after this is ready you should have 22.04