我们拥有配置了 Xorg / lightdm / xfce4 的最新 Debian Jesse 盒子。它们被设置为自动登录并在启动时运行一些程序。这通常工作得很好。
问题是在启动时没有插入显示器（由于 KVM 开关位置错误，或者只是忘记插入显示器电缆）。 Xorg 仍然启动，没有检测到监视器（如预期的那样），并且似乎以标称分辨率创建了一个未连接到任何视频输出的帧缓冲区。其他进程全部启动，输出到该帧缓冲区。Xorg.0.log显示这个：
[ 20.650] (II) intel(0): Output VGA1 has no monitor section
[ 20.651] (II) intel(0): Output HDMI1 has no monitor section
[ 20.651] (II) intel(0): Output DP1 has no monitor section
[ 20.652] (II) intel(0): EDID for output VGA1
[ 20.653] (II) intel(0): EDID for output HDMI1
[ 20.653] (II) intel(0): EDID for output DP1
[ 20.653] (II) intel(0): Output VGA1 disconnected
[ 20.653] (II) intel(0): Output HDMI1 disconnected
[ 20.653] (II) intel(0): Output DP1 disconnected
[ 20.653] (WW) intel(0): No outputs definitely connected, trying again...
...
[ 20.653] (WW) intel(0): Unable to find connected outputs - setting 1024x768 initial framebuffer
[ 20.653] (II) intel(0): Using default gamma of (1.0, 1.0, 1.0) unless otherwise stated.
[ 20.653] (II) intel(0): Kernel page flipping support detected, enabling
[ 20.653] (==) intel(0): DPI set to (96, 96)
如果我现在插入显示器，似乎 EDID 没问题，但视频输出仍然处于禁用状态。我可以ctrl-alt-F1获取文本控制台并登录，但无法弄清楚如何启用视频输出并获取附加到它的帧缓冲区。
xrandr -d :0 --prop说：
Screen 0: minimum 320 x 200, current 320 x 200, maximum 8192 x 8192
VGA1 connected (normal left inverted right x axis y axis)
EDID:
00ffffffffffff0010ac4a40554e4743
151401030a351e78ea9eb5a259559b25
0e5054a54b00714f8180d1c001010101
010101010101023a801871382d40582c
4500132a2100001e000000ff0031344b
304e30355043474e550a000000fc0044
454c4c2047323431300a2020000000fd
00384c1e5312000a202020202020009b
1920x1080 60.00 +
1280x1024 75.02 60.02
1152x864 75.00
1024x768 75.08 60.00
800x600 75.00 60.32
640x480 75.00 60.00
720x400 70.08
HDMI1 disconnected (normal left inverted right x axis y axis)
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
DP1 disconnected (normal left inverted right x axis y axis)
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
所以我们看到显示器现在连接到 VGA1。尝试xrandr -d :0 --output VGA1 --auto（以及各种模型行设置的变化）都会导致：
xrandr: Configure crtc 0 failed
我不明白这想告诉我什么......
两个问题/问题：
如果最初没有检测到显示器，是否有办法强制 Xorg 默认启用 VGA 输出，即使分辨率不太理想？
如果做不到这一点，如何在插入显示器后启用视频输出？
编辑：这是输出xrandr -d :0 --verbose：
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
VGA1 connected (normal left inverted right x axis y axis)
Identifier: 0x41
Timestamp: 21055
Subpixel: unknown
Clones: HDMI1
CRTCs: 0 1
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
EDID:
00ffffffffffff0010ac4a40554e4743
151401030a351e78ea9eb5a259559b25
0e5054a54b00714f8180d1c001010101
010101010101023a801871382d40582c
4500132a2100001e000000ff0031344b
304e30355043474e550a000000fc0044
454c4c2047323431300a2020000000fd
00384c1e5312000a202020202020009b
1920x1080 (0x99) 148.500MHz +HSync +VSync +preferred
h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.50KHz
v: height 1080 start 1084 end 1089 total 1125 clock 60.00Hz
1280x1024 (0x9a) 135.000MHz +HSync +VSync
h: width 1280 start 1296 end 1440 total 1688 skew 0 clock 79.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 75.02Hz
1280x1024 (0x9b) 108.000MHz +HSync +VSync
h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz
v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz
1152x864 (0x9c) 108.000MHz +HSync +VSync
h: width 1152 start 1216 end 1344 total 1600 skew 0 clock 67.50KHz
v: height 864 start 865 end 868 total 900 clock 75.00Hz
1024x768 (0x9d) 78.800MHz +HSync +VSync
h: width 1024 start 1040 end 1136 total 1312 skew 0 clock 60.06KHz
v: height 768 start 769 end 772 total 800 clock 75.08Hz
1024x768 (0x9e) 65.000MHz -HSync -VSync
h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz
v: height 768 start 771 end 777 total 806 clock 60.00Hz
800x600 (0x9f) 49.500MHz +HSync +VSync
h: width 800 start 816 end 896 total 1056 skew 0 clock 46.88KHz
v: height 600 start 601 end 604 total 625 clock 75.00Hz
800x600 (0xa0) 40.000MHz +HSync +VSync
h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz
v: height 600 start 601 end 605 total 628 clock 60.32Hz
640x480 (0xa1) 31.500MHz -HSync -VSync
h: width 640 start 656 end 720 total 840 skew 0 clock 37.50KHz
v: height 480 start 481 end 484 total 500 clock 75.00Hz
640x480 (0xa2) 25.200MHz -HSync -VSync
h: width 640 start 656 end 752 total 800 skew 0 clock 31.50KHz
v: height 480 start 490 end 492 total 525 clock 60.00Hz
720x400 (0xa3) 28.320MHz -HSync +VSync
h: width 720 start 738 end 846 total 900 skew 0 clock 31.47KHz
v: height 400 start 412 end 414 total 449 clock 70.08Hz
HDMI1 disconnected (normal left inverted right x axis y axis)
Identifier: 0x42
Timestamp: 21055
Subpixel: unknown
Clones: VGA1
CRTCs: 0 1
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on
DP1 disconnected (normal left inverted right x axis y axis)
Identifier: 0x43
Timestamp: 21055
Subpixel: unknown
Clones:
CRTCs: 0 1
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
Broadcast RGB: Automatic
supported: Automatic, Full, Limited 16:235
audio: auto
supported: force-dvi, off, auto, on