Error x11 display manager lightdm vs gdm3
When running manually sudo /usr/sbin/lightdm -d
(debug flag):
[+0.08s] DEBUG: Launching process 2956: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
[+0.08s] DEBUG: XServer 0: Waiting for ready signal from X server :0
[+0.08s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.08s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
[+0.09s] DEBUG: Process 2956 exited with return value 127
When running sudo /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
manually:
/usr/lib/xorg/Xorg: symbol lookup error: /usr/lib/xorg/Xorg: undefined symbol: drmGetEntry
ls -l /usr/lib/aarch64-linux-gnu/libdrm.*
lrwxrwxrwx 1 root root 11 May 11 2020 /usr/lib/aarch64-linux-gnu/libdrm.so -> libdrm.so.2
lrwxrwxrwx 1 root root 14 Jan 22 12:40 /usr/lib/aarch64-linux-gnu/libdrm.so.2 -> libdrm_nvdc.so
-rw-r--r-- 1 root root 63880 May 11 2020 /usr/lib/aarch64-linux-gnu/libdrm.so.2.4.0
grep drmGetEntry /usr/lib/aarch64-linux-gnu/libdrm.*
Binary file /usr/lib/aarch64-linux-gnu/libdrm.so.2.4.0 matches
Conclusion: X looks into libdrm.so or libdrm.so.2 but the symbol is in libdrm.so.2.4.0.
Fix:
sudo rm /usr/lib/aarch64-linux-gnu/libdrm.so.2 ; sudo cp /usr/lib/aarch64-linux-gnu/libdrm.so.2.4.0 /usr/lib/aarch64-linux-gnu/libdrm.so.2
Restart:
sudo service lightdm restart OR sudo reboot