Login Screen: "Failed to start session"

Support & Help Requests
1

After restarting my desktop (Ubuntu Mate 20.04) I cannot log in. I enter my password and it displays the message "Failed to start session" above the password text entry box. I don't know how to recover from this, and any help will be sincerely appreciated.

More Info: When I click the Accessibility icon in the top panel of the login screen, and select "Onscreen keyboard", nothing happens. One of the last things I did before this problem appeared was to use the Software app to remove what I believed were programs I don't need. One of those was the "Onboard" app, as well as the "Onboard Settings" app.

Is it possible that the login screen needs those apps installed in order to start a session? (If so, that may be a bug.) If that is the problem, then how do I reinstall those two apps if I cannot login?

Thanks,

Dave H.

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2

Welcome @DaveHighland to our community!

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I think it's fixed. Here's what happened:

From the login screen, I pressed Ctrl-Alt-F1 to get to the command line and tried reinstalling the Mate desktop:

 sudo apt reinstall mate-desktop
 sudo reboot

That didn't work. So I searched with apt, comparing results on another computer, and determined that several packages were missing:

 sudo apt install mate-desktop-environment
 sudo apt install mate-tweak
 sudo apt install mate-indicator-applet
 sudo apt install mate-indicator-applet-common
 sjudo reboot

And that worked. I have no idea how those packages went missing.

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