Xorg.0.logを調べてみました。

nvidiaのモジュールが読み込めていないみたいです。対処方法は分かりますでしょうか。


[    24.255]
X.Org X Server 1.16.0
Release Date: 2014-07-16
[    24.255] X Protocol Version 11, Revision 0
[    24.255] Build Operating System: Linux 3.2.0-70-generic i686 Ubuntu
[    24.255] Current Operating System: Linux ikegi-System-Product-Name 3.16.0-77-generic #99~14.04.1-Ubuntu SMP Tue Jun 28 19:18:41 UTC 2016 i686
[    24.255] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.16.0-77-generic root=UUID=ae41bcc6-4870-433a-8387-21a4e613e58e ro quiet splash vt.handoff=7
[    24.255] Build Date: 12 February 2015  11:11:29PM
[    24.255] xorg-server 2:1.16.0-1ubuntu1.2~trusty2 (For technical support please see http://www.ubuntu.com/support)
[    24.255] Current version of pixman: 0.30.2
[    24.255]     Before reporting problems, check http://wiki.x.org
    to make sure that you have the latest version.
[    24.255] Markers: (--) probed, (**) from config file, (==) default setting,
    (++) from command line, (!!) notice, (II) informational,
    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
[    24.255] (==) Log file: "/var/log/Xorg.0.log", Time: Sat Aug 27 10:14:30 2016
[    24.272] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[    24.272] (==) No Layout section.  Using the first Screen section.
[    24.537] (==) No screen section available. Using defaults.
[    24.537] (**) |-->Screen "Default Screen Section" (0)
[    24.537] (**) |   |-->Monitor "<default monitor>"
[    24.538] (==) No monitor specified for screen "Default Screen Section".
    Using a default monitor configuration.
[    24.538] (==) Automatically adding devices
[    24.538] (==) Automatically enabling devices
[    24.538] (==) Automatically adding GPU devices
[    24.538] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
[    24.538]     Entry deleted from font path.
[    24.538] (WW) The directory "/usr/share/fonts/X11/100dpi/" does not exist.
[    24.538]     Entry deleted from font path.
[    24.538] (WW) The directory "/usr/share/fonts/X11/75dpi/" does not exist.
[    24.538]     Entry deleted from font path.
[    24.538] (WW) The directory "/usr/share/fonts/X11/100dpi" does not exist.
[    24.538]     Entry deleted from font path.
[    24.538] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist.
[    24.538]     Entry deleted from font path.
[    24.538] (==) FontPath set to:
    /usr/share/fonts/X11/misc,
    /usr/share/fonts/X11/Type1,
    built-ins
[    24.538] (==) ModulePath set to "/usr/lib/i386-linux-gnu/xorg/extra-modules,/usr/lib/xorg/extra-modules,/usr/lib/xorg/modules"
[    24.538] (II) The server relies on udev to provide the list of input devices.
    If no devices become available, reconfigure udev or disable AutoAddDevices.
[    24.538] (II) Loader magic: 0xb7750660
[    24.538] (II) Module ABI versions:
[    24.538]     X.Org ANSI C Emulation: 0.4
[    24.538]     X.Org Video Driver: 18.0
[    24.538]     X.Org XInput driver : 21.0
[    24.538]     X.Org Server Extension : 8.0
[    24.538] (II) xfree86: Adding drm device (/dev/dri/card0)
[    24.539] (--) PCI:*(0:1:0:0) 10de:0640:1048:0f55 rev 161, Mem @ 0xfd000000/16777216, 0xd0000000/268435456, 0xfa000000/33554432, I/O @ 0x0000bc00/128, BIOS @ 0x????????/524288
[    24.539] (II) LoadModule: "glx"
[    24.615] (II) Loading /usr/lib/xorg/modules/extensions/libglx.so
[    24.853] (II) Module glx: vendor="X.Org Foundation"
[    24.853]     compiled for 1.16.0, module version = 1.0.0
[    24.853]     ABI class: X.Org Server Extension, version 8.0
[    24.853] (==) AIGLX enabled
[    24.853] (==) Matched nvidia as autoconfigured driver 0
[    24.853] (==) Matched nouveau as autoconfigured driver 1
[    24.853] (==) Matched nvidia as autoconfigured driver 2
[    24.853] (==) Matched nouveau as autoconfigured driver 3
[    24.853] (==) Matched modesetting as autoconfigured driver 4
[    24.853] (==) Matched fbdev as autoconfigured driver 5
[    24.853] (==) Matched vesa as autoconfigured driver 6
[    24.853] (==) Assigned the driver to the xf86ConfigLayout
[    24.853] (II) LoadModule: "nvidia"
[    24.860] (WW) Warning, couldn't open module nvidia
[    24.860] (II) UnloadModule: "nvidia"
[    24.860] (II) Unloading nvidia
[    24.860] (EE) Failed to load module "nvidia" (module does not exist, 0)
[    24.860] (II) LoadModule: "nouveau"

お騒がせしました。

/etc/X11/xinit/default-display-manager
を確認したらsddmになっていました。この環境が安定しているのではと考え
sudo dpkg-reconfigure sddm
としたらsddmではあるもののGUIになりました。これでとりあえず使えます。KDEにする方法は落ち着いて考えます。