运行 kubuntu 18.04，外部屏幕（东芝电视）通过 HDMI 电缆连接。Ubuntu 识别外部输出，并采取相应措施，但不会在外部屏幕上显示图像（笔记本电脑屏幕工作正常）。
xrandr 的输出：
Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 8192 x 8192
LVDS-1 connected primary 1366x768+1920+0 (normal left inverted right x axis y axis) 344mm x 194mm
1366x768 59.64*+
1360x768 59.80 59.96
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
VGA-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 708mm x 398mm
1920x1080 50.00 + 60.00* 59.94
1920x1080i 60.00 50.00 59.94
1280x1024 60.02
1360x768 60.02
1280x768 59.87 59.99
1280x720 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
800x600 72.19 75.00 60.32 56.25
720x576 50.00
720x576i 50.00
720x480 60.00 59.94
720x480i 60.00 59.94
640x480 75.00 72.81 60.00 59.94
DP-1 disconnected (normal left inverted right x axis y axis)
输出sudo lshw -C video：
*-display
description: VGA compatible controller
product: Core Processor Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 18
width: 64 bits
clock: 33MHz
capabilities: msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:30 memory:fa400000-fa7fffff memory:c0000000-cfffffff ioport:f080(size=8) memory:c0000-dffff
disper -l立即发生段错误。
输出lspci | grep -i vga：
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 18)