将 Ubuntu 升级到 18.04 后无法启动 Xorg

Question

将 Ubuntu 升级到 18.04（从 17.10 开始）后，Xorg 无法启动。它只是在黑色和灰色空白屏幕之间反复切换。我将 grub 重新配置为使用 nomodeset 以文本模式启动。startx 命令无法启动 Xorg 服务器。我有一个内置的英特尔显卡。这是 /var/log/Xorg.0.log 的输出：

[    38.698] (II) config/udev: Adding input device HDA Intel PCH HDMI/DP,pcm=3 (/dev/input/event10)
[    38.698] (II) No input driver specified, ignoring this device.
[    38.698] (II) This device may have been added with another device file.
[    38.698] (II) config/udev: Adding input device HDA Intel PCH HDMI/DP,pcm=7 (/dev/input/event11)
[    38.698] (II) No input driver specified, ignoring this device.
[    38.699] (II) This device may have been added with another device file.
[    38.699] (II) config/udev: Adding input device HDA Intel PCH Rear Mic (/dev/input/event5)
[    38.699] (II) No input driver specified, ignoring this device.
[    38.699] (II) This device may have been added with another device file.
[    38.699] (II) config/udev: Adding input device HDA Intel PCH Front Mic (/dev/input/event6)
[    38.699] (II) No input driver specified, ignoring this device.
[    38.699] (II) This device may have been added with another device file.
[    38.699] (II) config/udev: Adding input device HDA Intel PCH Line (/dev/input/event7)
[    38.699] (II) No input driver specified, ignoring this device.
[    38.699] (II) This device may have been added with another device file.
[    38.700] (II) config/udev: Adding input device HDA Intel PCH Line Out (/dev/input/event8)
[    38.700] (II) No input driver specified, ignoring this device.
[    38.700] (II) This device may have been added with another device file.
[    38.700] (II) config/udev: Adding input device HDA Intel PCH Front Headphone (/dev/input/event9)
[    38.700] (II) No input driver specified, ignoring this device.
[    38.700] (II) This device may have been added with another device file.
[    41.427] (**) Option "fd" "21"
[    41.427] (II) event1  - Power Button: device removed
[    41.427] (**) Option "fd" "24"
[    41.427] (II) event0  - Power Button: device removed
[    41.427] (**) Option "fd" "25"
[    41.427] (II) event2  - PixArt USB Optical Mouse: device removed
[    41.427] (**) Option "fd" "26"
[    41.427] (II) event3  -   USB Keyboard: device removed
[    41.427] (**) Option "fd" "27"
[    41.427] (II) event4  -   USB Keyboard: device removed
[    41.428] (II) UnloadModule: "libinput"
[    41.428] (II) systemd-logind: releasing fd for 13:68
[    41.444] (II) UnloadModule: "libinput"
[    41.444] (II) systemd-logind: releasing fd for 13:67
[    41.460] (II) UnloadModule: "libinput"
[    41.460] (II) systemd-logind: releasing fd for 13:66
[    41.512] (II) UnloadModule: "libinput"
[    41.512] (II) systemd-logind: releasing fd for 13:64
[    41.528] (II) UnloadModule: "libinput"
[    41.528] (II) systemd-logind: releasing fd for 13:65
[    41.653] (II) Server terminated successfully (0). Closing log file.

grep "(EE)" /var/log/Xorg.0.log 的输出：

[    86.288] (EE) open /dev/dri/card0: No such file or directory
[    86.289] (EE) open /dev/dri/card0: No such file or directory
[    86.289] (EE) Screen 0 deleted because of no matching config section.
[    86.294] (EE) AIGLX: reverting to software rendering