I am trying to upgrade from Ubuntu 18.04.5 to 20.04.1 via:

$ sudo do-release-upgrade

This fails as follows:

...

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This was likely caused by:

Unofficial software packages not provided by Ubuntu Please use the tool 'ppa-purge' from the ppa-purge package to remove software from a Launchpad PPA and try the upgrade again.

If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If you want to investigate this yourself the log files in '/var/log/dist-upgrade' will contain details about the upgrade. Specifically, look at 'main.log' and 'apt.log'.

The tail of /var/log/dist-upgrade/main.log contains the following error:

...
2020-10-11 18:36:30,320 WARNING Can't mark 'ubuntu-desktop' for upgrade (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
2020-10-11 18:36:31,747 ERROR Dist-upgrade failed: 'Broken packages after upgrade: colord'
2020-10-11 18:36:31,747 DEBUG abort called
2020-10-11 18:36:31,755 DEBUG openCache()
2020-10-11 18:36:37,070 DEBUG Comparing 4.15.0-117 with 
2020-10-11 18:36:37,071 DEBUG Comparing 4.15.0-118 with 4.15.0-117
2020-10-11 18:36:37,824 DEBUG /openCache(), new cache size 99980

Here are the reverse package dependencies of colord:

$ apt-cache rdepends colord
colord
Reverse Depends:
  colord-sensor-argyll
  gnome-control-center
    colord:i386
  cups-filters
    colord:i386
  cups-daemon
    colord:i386
  cups
    colord:i386
  xiccd
    colord:i386
  krita
    colord:i386
  gnome-color-manager
    colord:i386
  foomatic-filters
    colord:i386
  dispcalgui
    colord:i386
  diffoscope
    colord:i386
  colord-sensor-argyll
    colord:i386
  colord-sensor-argyll
  colord-data
  colord-sensor-argyll
    colord:i386
  argyll
    colord:i386
  libcolord2
    colord:i386
  libcolord-gtk1
    colord:i386
  gnome-control-center
    colord:i386
  cups-filters
    colord:i386
  cups-daemon
    colord:i386
  cups
    colord:i386
  colord-data

I recently had a segmentation fault issue with mesa and installed a version from ppa:kisak/kisak-mesa. This might cause the upgrade problem now.

The following would happen if I remove the colord package:

$ sudo apt-get remove colord 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  apg colord-data gnome-control-center-faces gnome-online-accounts libcolorhug2 libnss-myhostname linux-headers-4.15.0-117 linux-headers-4.15.0-117-generic
  linux-image-4.15.0-117-generic linux-modules-4.15.0-117-generic linux-modules-extra-4.15.0-117-generic python3-macaroonbakery python3-nacl
  python3-protobuf python3-pymacaroons python3-rfc3339 ubuntu-system-service
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  colord gnome-control-center ubuntu-desktop
0 upgraded, 0 newly installed, 3 to remove and 8 not upgraded.
After this operation, 5,782 kB disk space will be freed.
Do you want to continue? [Y/n]

This does not sound like a good idea because last time I removed ubuntu-desktop the UI did no longer start-up. See linked post.

Question

How can I resolve the upgrade problem without risking the segmentation fault to reincarnate?

Related

• Ubuntu 18.04.4 startup stuck after package updates / mesa segmentation fault
• Can't seem to upgrade to 20.04 from 18.04 due to held back packages: libsensors4, libsensors-config, colord
• libsensors5 or libsensors-config upgrade problem
• Upgrade from 18.04 to 20.04 failed ...

After all helpful hints, questions and comments I became inpatient with myself and decided to give the upgrade another try. Here is what I did:

1. sudo apt-get remove colord
2. sudo apt-get remove mesa-utils - This also removed ubuntu-desktop

This unblocked the do-release-upgrade command. No reboot at this step.

3. sudo do-release-upgrade

After ~2h of downloading the upgrade process requested a reboot. I confirmed. The upgrade went well - the system started.

After inspecting the new operating system I noticed that I could neither open the Settings nor change the background image nor could I install ubuntu-desktop or gnome-control-center. Also no files where shown on the Desktop although I could ls them in the folder.

After a while I figured that these packages where still blocked by some mesa packages originating from ppa:kisak/kisak-mesa.

4. I decided to completely remove all mesa package via Synaptic Package Manager
5. sudo apt-get install gnome-control-center which transitively installed mesa packages
6. sudo apt-get install ubuntu-desktop
7. Reboot.

After restarting the system all files on the Desktop where shown, I was able to launch the Settings and change the background image. - Thank you everyone!

For people who need it: sudo apt-get update --fix-missing; sudo dpkg --configure -a; sudo apt-get install -f; sudo fuser -vki /var/lib/dpkg/lock; sudo dpkg --configure -a;