我使用旧 PC 设置了无头 Ubuntu 16.04 服务器。如果安装了显卡（即使没有显示器），一切都很好。我可以通过 SSH 或从 LAN 对其进行 ping。如果我移除显卡，服务器将无法访问。SSH 将收到操作超时错误。Ping 将收到“主机已关闭”错误。
我可以通过日志确认 BIOS 没有阻止 Ubuntu 启动：
Jan 6 21:45:03 centaurus kernel: [ 20.097907] audit: type=1400 audit(1483710302.488:10): apparmor="STATUS" operation="profile_load" profile="unconfined" name="lxc-container-default-with-nesting" pid=746 comm="apparmor_parser"
Jan 6 21:45:03 centaurus kernel: [ 20.106215] audit: type=1400 audit(1483710302.496:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/bin/ubuntu-core-launcher" pid=749 comm="apparmor_parser"
Jan 6 21:45:03 centaurus kernel: [ 20.643765] cgroup: new mount options do not match the existing superblock, will be ignoredi
*I pressed the powerbutton to shutdown (gracefully)
*I installed the graphics card and turned on
Jan 6 21:48:16 centaurus kernel: [ 0.000000] Initializing cgroup subsys cpuset
Jan 6 21:48:16 centaurus kernel: [ 0.000000] Initializing cgroup subsys cpu
Jan 6 21:48:16 centaurus kernel: [ 0.000000] Initializing cgroup subsys cpuacct
这是安装显卡后的（部分）启动日志：
Jan 6 21:48:16 centaurus kernel: [ 20.278940] audit: type=1400 audit(1483710493.640:10): apparmor="STATUS" operation="profile_load" profile="unconfined" name="lxc-container-default-with-nesting" pid=738 comm="apparmor_parser"
Jan 6 21:48:16 centaurus kernel: [ 20.287161] audit: type=1400 audit(1483710493.648:11): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/bin/ubuntu-core-launcher" pid=741 comm="apparmor_parser"
Jan 6 21:48:16 centaurus kernel: [ 20.377338] r8169 0000:03:00.0 enp3s0: link down
Jan 6 21:48:16 centaurus kernel: [ 20.377340] r8169 0000:03:00.0 enp3s0: link down
Jan 6 21:48:16 centaurus kernel: [ 20.377395] IPv6: ADDRCONF(NETDEV_UP): enp3s0: link is not ready
Jan 6 21:48:16 centaurus kernel: [ 21.513511] cgroup: new mount options do not match the existing superblock, will be ignored
Jan 6 21:48:16 centaurus kernel: [ 22.467902] r8169 0000:03:00.0 enp3s0: link up
Jan 6 21:48:16 centaurus kernel: [ 22.467917] IPv6: ADDRCONF(NETDEV_CHANGE): enp3s0: link becomes ready
我可以看到有一些额外的行显示以太网正在运行。那么如何在没有 GPU 的情况下使其可访问？