Gfilui

My Ubuntu Server 18.04 system, while it continues to work, has become unable to apply any updates. I'm not aware of any system change that I made that could be the culprit.

What can I do to fix this? I've tried autoremove, purge, etc.

Here is typical output but any apt command produces a similar error:

# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be REMOVED:
 linux-image-4.15.0-22-generic
The following packages will be upgraded:
 libcephfs2 librados2 ssh-import-id
3 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
1 not fully installed or removed.
Need to get 0 B/3,065 kB of archives.
After this operation, 8,281 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 149817 files and directories currently installed.)
Removing linux-image-4.15.0-22-generic (4.15.0-22.24) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-4.15.0-22-generic
/etc/kernel/postrm.d/x-grub-legacy-ec2:
Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ...

Could not find /boot/grub/menu.lst file. Would you like /boot/grub/menu.lst generated for you? (y/N) /usr/sbin/update-grub-legacy-ec2: line 1101: read: 
read error: 0: Bad file descriptor
run-parts: /etc/kernel/postrm.d/x-grub-legacy-ec2 exited with return code 1
dpkg: error processing package linux-image-4.15.0-22-generic (--remove):
 installed linux-image-4.15.0-22-generic package post-removal script 
subprocess returned error exit status 1
Errors were encountered while processing:
 linux-image-4.15.0-22-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)

Thanks to all for the responses. Followed suggestions below. Can't seem to clean it up via apt / dpkg. Here is output:

# sudo update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.15.0-22-generic
Found initrd image: /boot/initrd.img-4.15.0-22-generic
Found linux image: /boot/vmlinuz-4.15.0-20-generic
Found initrd image: /boot/initrd.img-4.15.0-20-generic
done

# sudo dpkg --purge linux-image-4.15.0-22-generic
dpkg: dependency problems prevent removal of linux-image-4.15.0-22-generic:
 linux-image-generic depends on linux-image-4.15.0-22-generic.
 linux-modules-extra-4.15.0-22-generic depends on linux-image-4.15.0-22-generic | linux-image-unsigned-4.15.0-22-generic; however:
 Package linux-image-4.15.0-22-generic is to be removed.
 Package linux-image-unsigned-4.15.0-22-generic is not installed.

dpkg: error processing package linux-image-4.15.0-22-generic (--purge): 

dependency problems - not removing
Errors were encountered while processing:
linux-image-4.15.0-22-generic

I am still unclear on why I experienced this issue, but it seems a missing grub /boot/grub/menu.lst file was causing apt / dpkg updates to fail. So I created an empty file.

sudo touch /boot/grub/menu.lst
sudo update-grub2

All good. Then proceed with updating the system:

apt update
apt upgrade
apt autoremove --purge

Along the way, there will be a warning that the current menu.lst file is different than the package maintainer's version. Select the option to install the package maintainer's version, and then the rest of the update and cleanup completes successfully. Will see how the next kernel upgrade goes, but problem is solved for now.

Thank you to all who contributed suggestions and help!

I know this should be a comment but I don't have enough reputation.

But I want to let you know I had a similar problem yesterday.

If this answer doesn't work for you, you can contact @videonauth . He's the super nice guy who helped me with this issue.

I will copypaste from his answer the part that will hopefully help you:

First remove the removable packages after having run an update to get
the proper package archives updated:

sudo apt update
sudo apt autoremove --purge

This should remove all removable packages so far except the one which
managed to get messed up which we can then remove then by installing
it and then removing it properly:

cd /var/cache/apt/archives
sudo dpkg -i linux-modules-4.15.0-22-generic_4.15.0-22.24_amd64.deb
sudo dpkg -r linux-modules-4.15.0-22-generic_4.15.0-22.24_amd64.deb 

(Note from Oussema: ^This command was used based on the fact that my system's architecture is amd64. You can see yours using the command uname -a
"i386", "i486", "i586" and "i686" and "athlon" all mean 32 bit.
"x86_64" means 64 bit (Opteron or Athlon-64). "i686-64" means 32-bit
operation with 64-bit address space (Intel 686 with the new memory
mechanism). )

Now cleaning up the archives by running:

sudo apt clean

And now we can reinstall the packages properly after having run an
complete update process:

sudo apt update
sudo apt dist-upgrade

with the following line:

sudo apt install --reinstall linux-generic