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Big disclaimer: Before this happened, I accidentally removed an important library (libreadline7), which has removed several important system libraries without me realizing (things like NetworkManager were also removed), which made Ubuntu stop booting properly. I was able to recover from this for my user by entering recovery mode from the bootloader,reinstalling ubuntu-minimal, ubuntu-standard, and ubuntu-mate-desktop. This allowed me to login to my own personal user and everything seemed to be mostly back to normal, however I'm sure some other things are broken, which is why I'm mentioning this.

I have an Ubuntu MATE 18.04 desktop installation with multiple users. For some reason, I am able to login to one user, which was the main user that was configured with the Ubuntu MATE installation. But the other user is unable to login into his MATE session.

After checking some logs in /var/log/lightdm, I could not find anything wrong with the lightdm, and I was led to the user's .xsession-errors file.

I noticed that in the .xsession-errors for that user, there are some errors that don't appear with my user

mate-session[18804]: WARNING: Unable to find provider 'mate-panel' of required component 'panel'
mate-session[18804]: WARNING: Unable to find provider 'caja' of required component 'filemanager'
mate-session[18804]: WARNING: Unable to find provider '' of required component 'dock'
mate-session[18804]: WARNING: Could not launch application 'update-notifier.desktop': Unable to start application: Failed to execute child process “update-notifier” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'snap-userd-autostart.desktop': Unable to start application: Failed to execute child process “/usr/bin/snap” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'print-applet.desktop': Unable to start application: Failed to execute child process “system-config-printer-applet” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'nm-applet.desktop': Unable to start application: Failed to execute child process “nm-applet” (No such file or directory)
sh: 1: /usr/bin/nvidia-settings: not found
mate-session[18804]: WARNING: Could not launch application 'blueman.desktop': Unable to start application: Failed to execute child process “blueman-applet” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'org.gnome.DejaDup.Monitor.desktop': Unable to start application: Failed to execute child process “/usr/lib/deja-dup/deja-dup-monitor” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'ubuntu-mate-welcome-autostart.desktop': Unable to start application: Failed to execute child process “/snap/bin/ubuntu-mate-welcome” (No such file or directory)
mate-session[18804]: WARNING: Could not launch application 'caja-dropbox.desktop': Unable to start application: Failed to execute child process “caja-dropbox” (No such file or directory)

(process:19290): indicator-sound-WARNING **: 14:39:55.272: volume-control-pulse.vala:735: unable to get pulse unix socket: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.PulseAudio1 was not provided by any .service files
Window manager warning: Log level 128: Name com.canonical.AppMenu.Registrar does not exist on the session bus

Window manager warning: Log level 16: XPresent is not compatible with your current system configuration.
Gtk-Message: 14:41:55.124: GtkDialog mapped without a transient parent. This is discouraged.
Gtk-Message: 14:42:12.848: GtkDialog mapped without a transient parent. This is discouraged.
Xsession: X session started for root at Sun Sep 26 12:24:13 +04 2021
dbus-update-activation-environment: systemd --user not found, ignoring --systemd argument
dbus-update-activation-environment: setting DISPLAY=:0
dbus-update-activation-environment: setting XAUTHORITY=/home/santhosh/.Xauthority
localuser:root being added to access control list
localuser:boinc being added to access control list
/etc/X11/xinit/xinitrc: 2: [: x: unexpected operator
/etc/X11/xinit/xinitrc: 2: [: x: unexpected operator
dbus-update-activation-environment: systemd --user not found, ignoring --systemd argument
dbus-update-activation-environment: setting GTK_MODULES=gail:atk-bridge
/etc/X11/xinit/xinitrc: 16: /etc/X11/Xsession.d/90gpg-agent: gpgconf: not found
/etc/X11/xinit/xinitrc: 18: /etc/X11/Xsession.d/90gpg-agent: gpgconf: not found
dbus-update-activation-environment: systemd --user not found, ignoring --systemd argument
dbus-update-activation-environment: setting QT_ACCESSIBILITY=1
dbus-update-activation-environment: systemd --user not found, ignoring --systemd argument
dbus-update-activation-environment: setting SUDO_GID=1002
dbus-update-activation-environment: setting MAIL=/var/mail/root
dbus-update-activation-environment: setting LC_TIME=en_US.UTF-8
dbus-update-activation-environment: setting USER=root

I figured that there might be an issue with the user's dconf database, but I couldn't figure it out. At this point I'm not sure what to check next. Is there a way to reconfigure the user's X session settings back to defaults?

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  • 1
    For deeper repair please run sudo apt-get install ubuntu-mate-desktop^ --reinstall and then report back.
    – N0rbert
    Sep 26, 2021 at 12:14
  • 1
    FYI: Ubuntu-MATE 18.04 LTS is no longer supported; refer ubuntu-mate.community/t/… or fridge.ubuntu.com/2020/08/14/ubuntu-18-04-5-lts-released where you'll note only Ubuntu Server, Ubuntu Desktop & Ubuntu Cloud come with 5 years of support; flavors only had shorter lives. I'd suggest using ubuntu-support-status to assess the security status of your actual install. Your question is still on-topic here, but consider how much security matters to you and the results of prior command. You're now using Ubuntu 18.04 LTS with MATE
    – guiverc
    Sep 26, 2021 at 12:24
  • Interesting, I was not aware that flavors have shorter lives. Thank you for that information. However, from what I understand the ubuntu base is still supported when it comes to security updates, and that's good enough for me. I prefer having a stable install for now even if the desktop packages are a little old
    – 9a3eedi
    Sep 26, 2021 at 12:38
  • 1
    In current situation we need to repair current Ubuntu (MATE) 18.04 LTS system before going to some way forward. I'm running about 20+ Ubuntu MATE 18.04 LTS and I really do not care about its 3-year support frame. I do not plan to upgrade it to 20.04 LTS, because of Qt4, python2 and so on. I'll upgrade to 22.04 LTS when it was released. So @9a3eedi may also stay on 18.04 LTS after its repair.
    – N0rbert
    Sep 26, 2021 at 12:50

2 Answers 2

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You have to fully reinstall Ubuntu MATE desktop task-package by

sudo apt-get install ubuntu-mate-desktop^ --reinstall

Note: the ^ in the end of ubuntu-mate-desktop^ means task, so ubuntu-mate-desktop package will be reinstalled with all its dependencies forcibly.

Then carefully reinstall things which are mentioned in the xsession-errors log:

sudo apt-get install --reinstall mate-panel caja update-notifier snapd \
mate-dock-applet system-config-printer network-manager-gnome blueman deja-dup \
caja-dropbox gpgconf

and

sudo snap install software-boutique --classic
sudo snap install ubuntu-mate-welcome --classic

then reboot and try to login using ordinary (not root) user.

After successful login you have to run debsums to reinstall corrupted/removed files which came from deb-packages by using commands below

sudo apt-get install debsums

followed by

xargs -rd '\n' -a <(sudo debsums -c 2>&1 | cut -d " " -f 4 | sort -u | xargs -rd '\n' -- dpkg -S | cut -d : -f 1 | sort -u) -- sudo apt-get install -f --reinstall --

(formatted as inline code for readabilty, please do not edit)


Problems with login of otheruser may be caused by permissions issue. Restore them to defaults using sudo chown -R otheruser:otheruser /home/otheruser (replace otheruser with correct username) and then reboot.

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  • what's the difference between reinstalling with and without a ^?
    – 9a3eedi
    Sep 26, 2021 at 12:42
  • 1
    ubuntu-mate-desktop^ is a special task package, it will install all dependencies forcibly. While reinstallation of ubuntu-mate-desktop will not touch its dependencies. Please run all commands from my answer exactly as they written and report back. I'm ready to help further if you get new problems (hope that they do not really occur).
    – N0rbert
    Sep 26, 2021 at 12:43
  • I have run your steps exactly as you listed it. I haven't seen any errors, apart from the following minor error: snap "software-boutique" is already installed, see 'snap help refresh'. The final command with debsums did not yield any errors or output. However, I am still unable to login to the other user's desktop with the exact same issue. (I am able to login to my user's desktop however)
    – 9a3eedi
    Sep 26, 2021 at 16:18
  • 1
    You have to check permissions in /home/otheruser or simply restore them to defaults using sudo chown -R otheruser:otheruser /home/otheruser (replace otheruser with correct username) and then reboot. If error persists please share updated error logs.
    – N0rbert
    Sep 26, 2021 at 16:23
  • running chown -R otheruser:otheruser /home/otheruser did the trick. I'm not sure how it got corrupted in the first place... Thank you very much! I would suggest adding that to your answer.
    – 9a3eedi
    Sep 27, 2021 at 6:52
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For anyone else that has this issue. I fixed it due to an issue with my previous theme, I had customised it and it was no longer supported in the latest version.

If I ran mate-panel it would segfault. If I moved the .config directory I'd get CAIRO_REFERENCE_COUNT_HAS_REFERENCE I tried all the things of updating or reinstalling mate, no luck. No luck with mate-panel --replace or reset.

I accidentally ran mate-panel as sudo and it worked. Which made me look at other things. mate-session-properties had some duplicate startup items, like two volumes, so I unticked the duplicates. mate-panel still didn't work.

I ran mate-appearance-properties and selected a default theme from the custom. mate-panel now ran, but I had to re-setup all my shortcuts.

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