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I know there are lots of answers re. removing the Kubuntu desktop. However, I haven't found one that solves the following problem.

Original installation was 18.04, and I subsequently installed the Kubuntu desktop because I thought it might solve an ongoing slow performance issue. It didn't, so I removed it as best I could using Synaptic (complete removal of all the KDE* packages and dependencies).

The remaining issue is that on boot-up, I still see the 'kubuntu' banner, followed by the on-screen keyboard at the login screen (it's not a touch-screen). When I 'drop' the keyboard, the login screen is similar to the Kubuntu version, albeit with no 'Plasma' session option.

I can login OK, and I get the original Gnome desktop, and a popup which tells me there has been a system error, but not what it was.

So, how do I restore the login screen to the Gnome(?) version, and how do I find out what the system error is?

many thanks,

John

John M.
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  • Kubuntu package is not at all recommended to be installed with Ubuntu. I once installed the latte-dock [https://askubuntu.com/questions/1278826/i-installed-latte-dock-and-a-lot-of-kde-apps-got-installed] which has a lot of kde dependencies, even after removing every kde package, I still had a lot of bits just like you left in the system(breeze cursors, icons, fonts, etc). The best thing I could do was reinstall ubuntu. – Heisenberg Dec 16 '20 at 13:36
  • Is it possible to reinstall Ubuntu without overwriting all my documents & emails etc? Just the OS, in other words? – John M. Dec 16 '20 at 14:01
  • Yeah, sure. You can make the backup of the home directory if you want. Or just manually copy the important stuff from the home folder and keep that in a different partition – Heisenberg Dec 17 '20 at 06:26

1 Answers1

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Indeed, it is difficult to remove all packages of an additional installed desktop if you do not have a list of all desktop packages that were installed.

When installing an entire desktop, e.g. with the command sudo apt install kubuntu-desktop, all dependent packages are automatically installed if they are not yet installed on the system. The command shows all these packages, then asks you for confirmation to proceed. I usually copy that entire list of packages to a text file, so I could use the list to remove them all again if I wished to remove the desktop.

Removing KDE packages

If you did not do that, then it becomes more difficult. sudo apt autoremove will remove all packages that were marked as "automatically installed" as a dependency of some package. However, when you install the kubuntu-desktop metapackage, most main applications will be marked as manually installed, so removing it and issuing an autoremove will remove little.

The best you can do is to use a graphical package manager such as Synaptic package manager to inspect all your installed packages, and gradually remove packages. Note carefully what other packages would be removed before proceeding: if you attempt to remove a package and you see that also ubuntu-desktop would be removed, then you know you should keep away.

Use the Ubuntu default login manager GDM

To revert to the default login manager, issue the command sudo dpkg-reconfigure gdm3. A dialog appears, in which you should select gdm3.

Restore the default Ubuntu boot screen

Your Ubuntu splash screen will be restored with the command sudo apt purge plymouth-theme-kubuntu-logo plymouth-theme-kubuntu-text.

Alternative approach: reinstall the system

A more intrusive approach to clean up would be to reinstall. In your case, a reinstall may solve the "slow performance" you experience.

It is possible to reinstall and leave your user configuration and user data in place. To achieve that, you need to select "Something else" in the installer, and then indicate the partitions yourself. Then, you can uncheck "format". In that scenario, the installer will reinstall the system on the same partition without erasing it first. The end result is that your data, user configuration and additionally installed applications, etc. will be preserved. All system configuration, however, will be freshly rewritten.

  • Do that only with an installation USB or DVD of the same Ubuntu version.
  • This is a "less clean" approach: there will be less chance that that may resolve your performance issue.

Remove error message at startup

The "system error" at start up may be minor if otherwise the system is working well. The dialog is provided by the Apport service. You can disable Apport (and ignore such error messages) according to this post.

vanadium
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  • We can check the APT logs and find the packages installed right? – Random Person Dec 16 '20 at 14:19
  • Excellent answer from Vanadium. Wish I had that level of knowledge. Ubuntu banner and login screen fully restored. Remaining issue: popup message after login + desktop displayed: "System program problem detected. Do you want to report the problem now?". Which log file should I look at? – John M. Dec 16 '20 at 14:34
  • You can disable "Apport" to get rid of the message, but that does not solve the cause, which may be minor and of less practical importance. In principle, you can click a button on this dialog to see some more information. I added this to the answer – vanadium Dec 16 '20 at 16:01
  • Thank you. It turned out to be reporting an earlier crash of summat called whoopsie. I deleted the (old) crash report and everything is good. Except the speed, which I thought was down to Firefox, but I now believe is down to the network chip; I'll raise a separate question for that though. Thanks again. – John M. Dec 18 '20 at 11:23