[mythtv-users] kernels

[Stephen Worthington]

On Wed, 21 Oct 2020 13:11:03 -0400, you wrote:

>this morning I find I can only boot on the older kernel: 5.4.0-51, but not
>5.4.0-52, after a couple hard restarts, I get "initramfs unpacking failed
>decoding failed"
>"kernel panic   not syncing   no working unit found"
>"try passing init=option to kernel"
>"see linux documentation/admin/guide/init.rst for guidance"
>
>Questions are: 1)Do I leave it running 24/7?
>
>                         2)Do I reconfigure grub, as in "
>https://www.systutorials.com/how-to-make-grub2-boot-to-older-kernel-version-in-ubuntu-20-04/
>"?
>
>                          3)Or, is there a way to repair the uncooperative
>kernel?
>
>TIA  Daryl    Ubuntu 20.04 mythtv 31 fixes.
>P.S. this time it isn't because of my mucking around, a couple of times
>over the past ten days I found the box stuck on the boot logo and a hard
>reboot worked, so I would guess a slow deprecation?

I would use the Synaptic package manager to just manually uninstall
the bad kernel's packages.  If you do not have synaptic installed, do
this to install it:

sudo apt-get install synaptic apt-xapian-index
sudo update-apt-xapian-index -vf

The apt-xapian-index package is the "Quick index" feature for Synaptic
- it is vital to have for searching for the right kernel packages to
remove.

Then when you run Synaptic, put this in the small "Quick search" field
at the top:

linux-kernel-5.4.0-52

then click on the "Status" button at the bottom left, and then on the
"Installed" option in the column above that button.  You should get a
list of all the installed packages for that kernel.  The packages you
will have will depend a bit on your hardware.  There are always the
three basic packages: linux-image-<xxx>, linux-headers-<xxx> and
linux-headers-<xxx>-<kernel type>, where xxx is the kernel number
("5.4.0-52" in this case) and the <kernel type> will normally be
"generic" unless you have installed a special kernel for some reason.
You may also have linux-modules-<xxx>-<kernel type> and some variants
of all those names with "extra" or "extras" in them.  You can click on
one of them, do Ctrl-A to select them all, then Right-Mouse-Button and
click on "Mark for reinstallation" or "Mark for complete removal".
Then click on the Apply button at the top.  I would suggest trying the
"Mark for reinstallation" option first, and if that does not fix
things, just completely remove those packages for now.  Hopefully if
this is a kernel bug or a bug in the packaging of the kernel, a fixed
version will be along shortly and you can upgrade to that.

When you had to do a hard reboot, did you run fsck -C -f on all the
partitions that were mounted at the time?  If not, any of them may
have some corruption in the filesystem, which could be a reason for
initramfs being corrupt.  So I would recommend booting a live image of
Ubuntu 20.04 and from there running fsck -C -f on all the partitions,
especially the boot partition, before you do anything else like
reinstalling the kernel.  If there are any errors to be repaired,
repeat the fsck again and again until there are no errors reported.

Also, if mythbackend was recording at the time you did a hard reboot,
the recordedseek table will very likely be crashed and if you are
unlucky other database tables could be also.  So after you do the
fscks, when you reboot into the normal system, do this to repair the
database files:

sudo systemctl stop mythtv-backend
cd /etc/cron.weekly

(or wherever you have your optimize_mythdb file - you may have moved
it to /etc/cron.daily)

sudo ./optimize_mythdb
sudo systemctl start mythtv-backend