[PLASMA 5] KDE Plasma login service failed - login loop in SDDM

[diegoaarondv]

When I log in to my laptop with Kubuntu 20.10, I enter the password and wait for the desktop window to load but it does not show and it returns me to the initial login window. I ran the test several times thinking that you had misspelled the password but got the same result.

Using CTRL + ALT + F2 I enter a console and log in without problems. From there I started the server x (startx command) and I was able to enter the desktop.

Since when I log in with the password it seems for a few seconds that it is loading the desktop but in the end it returns me to the login window again

I tried with this tutorial https://letsfoss.com/ubuntu-20-04-login-loop-fix/ but the problem persist

I use the command journalctl -b -u sddm for view the proccess of display manager and the log is:

-- Logs begin at Thu 2020-09-24 14:27:12 -05, end at Mon 2020-12-07 16:17:13 -05. --
dic 07 16:14:12 laptop systemd[1]: Starting Simple Desktop Display Manager...
dic 07 16:14:12 laptop systemd[1]: Started Simple Desktop Display Manager.
dic 07 16:14:17 laptop sddm[761]: Initializing...
dic 07 16:14:17 laptop sddm[761]: Starting...
dic 07 16:14:17 laptop sddm[761]: Logind interface found
dic 07 16:14:17 laptop sddm[761]: Adding new display on vt 1 ...
dic 07 16:14:17 laptop sddm[761]: Loading theme configuration from ""
dic 07 16:14:17 laptop sddm[761]: Display server starting...
dic 07 16:14:17 laptop sddm[761]: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{7f0a3c64-7670-4435-a580-19891a3af1f8} -background none -noreset -displayfd 17 -seat seat0 vt1
dic 07 16:14:24 laptop sddm[761]: Setting default cursor
dic 07 16:14:25 laptop sddm[761]: Running display setup script  "/usr/share/sddm/scripts/Xsetup"
dic 07 16:14:25 laptop sddm[761]: Display server started.
dic 07 16:14:25 laptop sddm[761]: Socket server starting...
dic 07 16:14:25 laptop sddm[761]: Socket server started.
dic 07 16:14:25 laptop sddm[761]: Loading theme configuration from "/usr/share/sddm/themes/ubuntu-theme/theme.conf"
dic 07 16:14:25 laptop sddm[761]: Greeter starting...
dic 07 16:14:25 laptop sddm[761]: Adding cookie to "/var/run/sddm/{7f0a3c64-7670-4435-a580-19891a3af1f8}"
dic 07 16:14:25 laptop sddm-helper[870]: [PAM] Starting...
dic 07 16:14:25 laptop sddm-helper[870]: [PAM] Authenticating...
dic 07 16:14:25 laptop sddm-helper[870]: [PAM] returning.
dic 07 16:14:25 laptop sddm-helper[870]: pam_unix(sddm-greeter:session): session opened for user sddm by (uid=0)
dic 07 16:14:26 laptop sddm[761]: Greeter session started successfully
dic 07 16:14:29 laptop sddm[761]: Message received from greeter: Connect
dic 07 16:14:48 laptop sddm[761]: Message received from greeter: Login
dic 07 16:14:48 laptop sddm[761]: Reading from "/usr/share/xsessions/plasma.desktop"
dic 07 16:14:48 laptop sddm[761]: Reading from "/usr/share/xsessions/plasma.desktop"
dic 07 16:14:48 laptop sddm[761]: Session "plasma.desktop" selected, command: "/usr/bin/startplasma-x11"
dic 07 16:14:48 laptop sddm-helper[967]: [PAM] Starting...
dic 07 16:14:48 laptop sddm-helper[967]: [PAM] Authenticating...
dic 07 16:14:48 laptop sddm-helper[967]: [PAM] Preparing to converse...
dic 07 16:14:48 laptop sddm-helper[967]: [PAM] Conversation with 1 messages
dic 07 16:14:48 laptop sddm-helper[967]: pam_kwallet5(sddm:auth): (null): pam_sm_authenticate
dic 07 16:14:48 laptop sddm-helper[967]: [PAM] returning.
dic 07 16:14:48 laptop sddm[761]: Authenticated successfully
dic 07 16:14:48 laptop sddm-helper[967]: pam_kwallet5(sddm:setcred): pam_kwallet5: pam_sm_setcred
dic 07 16:14:48 laptop sddm-helper[967]: pam_unix(sddm:session): session opened for user diego by (uid=0)
dic 07 16:14:48 laptop sddm-helper[967]: pam_kwallet5(sddm:session): pam_kwallet5: pam_sm_open_session
dic 07 16:14:49 laptop sddm[761]: Auth: sddm-helper exited successfully
dic 07 16:14:50 laptop sddm-helper[967]: pam_unix(sddm:session): session closed for user diego
dic 07 16:14:49 laptop sddm[761]: Greeter stopped.
dic 07 16:14:50 laptop sddm-helper[967]: pam_kwallet5(sddm:session): pam_kwallet5: pam_sm_close_session
dic 07 16:14:50 laptop sddm-helper[967]: pam_kwallet5(sddm:setcred): pam_kwallet5: pam_sm_setcred
dic 07 16:14:49 laptop sddm-helper[967]: Starting: "/etc/sddm/Xsession \"/usr/bin/startplasma-x11\""
dic 07 16:14:50 laptop sddm[761]: Session started
dic 07 16:14:50 laptop sddm-helper[967]: [PAM] Closing session
dic 07 16:14:50 laptop sddm-helper[967]: [PAM] Ended.
dic 07 16:14:50 laptop sddm[761]: Auth: sddm-helper exited with 127
dic 07 16:14:50 laptop sddm[761]: Socket server stopping...
dic 07 16:14:50 laptop sddm[761]: Socket server stopped.
dic 07 16:14:50 laptop sddm[761]: Display server stopping...
dic 07 16:14:52 laptop sddm[761]: Display server stopped.
dic 07 16:14:52 laptop sddm[761]: Running display stop script  "/usr/share/sddm/scripts/Xstop"
dic 07 16:14:52 laptop sddm[761]: Removing display ":0" ...
dic 07 16:14:52 laptop sddm[761]: Adding new display on vt 1 ...
dic 07 16:14:52 laptop sddm[761]: Loading theme configuration from ""
dic 07 16:14:52 laptop sddm[761]: Display server starting...
dic 07 16:14:52 laptop sddm[761]: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{30b9b966-e253-492d-a0a6-f08cec746f61} -background none -noreset -displayfd 18 -seat seat0 vt1
dic 07 16:14:53 laptop sddm[761]: Setting default cursor
dic 07 16:14:53 laptop sddm[761]: Running display setup script  "/usr/share/sddm/scripts/Xsetup"
dic 07 16:14:53 laptop sddm[761]: Display server started.
dic 07 16:14:53 laptop sddm[761]: Socket server starting...
dic 07 16:14:53 laptop sddm[761]: Socket server started.
dic 07 16:14:53 laptop sddm[761]: Loading theme configuration from "/usr/share/sddm/themes/ubuntu-theme/theme.conf"
dic 07 16:14:53 laptop sddm[761]: Greeter starting...
dic 07 16:14:53 laptop sddm[761]: Adding cookie to "/var/run/sddm/{30b9b966-e253-492d-a0a6-f08cec746f61}"
dic 07 16:14:53 laptop sddm-helper[1030]: [PAM] Starting...
dic 07 16:14:53 laptop sddm-helper[1030]: [PAM] Authenticating...
dic 07 16:14:53 laptop sddm-helper[1030]: pam_unix(sddm-greeter:session): session opened for user sddm by (uid=0)
dic 07 16:14:53 laptop sddm-helper[1030]: [PAM] returning.
dic 07 16:14:53 laptop sddm[761]: Greeter session started successfully
dic 07 16:14:53 laptop sddm[761]: Message received from greeter: Connect

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Which route of validations should you review in order to find the solution since I have run out of ideas

[jlittle]

An easy thing to try is to add a new user, and see if the problem occurs for that user. If it doesn't, there's something in your user that is causing trouble.

I suspect the problem is not in sddm, but in X or KDE; if they crash early you land back at the login screen. I suggest a look at the Xorg log in /var/log/Xorg.0.log, and maybe ~/.xsession-errors (you might have to look via the linux console login, startx might clear them).