Fatal server error:Server is already active for display 0

Fedora在啟動過程中完全正常，未有任何錯誤提示。但會轉到字元介面的登入提示下，而不是X Window的登入介面。

使用startx命令啟動X Window失敗，提示如下：

Fatal server error:

Server is already active for display 0

If this server is no longer running, remove /tmp/.X0-lock and start again

排錯過程：

1. 檢查是否只有一個X server在運行。

The number denotes the display number (in this case 0). This number needs to be unique on the system, so you cannot run two servers on one system with identical display numbers. This message indicates that there is already a server with this number running
on the system. 

檢查方法：

You can verify this by running 

 ps aux | grep `cat /tmp/.X0-lock`

如果有類似的輸出，則表明確實有一個Xserver正在運行

If you see an output like: 

root  2283  0.5  5.1 27796 6536 ?    S  Apr21  59:03 [X]

it indicates that there is indeed an Xserver running under this PID.

解決方案：

 To start a second server on the same system you have to give it a different dislay number. 

If you start your servers using startx you can do：

startx -- :1

to start a server with display number 1. 

2. 沒有Xserver在運行時，刪除tmp/.X0-lock檔案，然後再startx

If you are sure there is no other server running on your system and above ps command indicates that no server with this PID is running, you should remove the file /tmp/.X0-lock by doing (as 'root'): 

rm -rf /tmp/.X0-lock

需要用root許可權才能刪除，其中-f 表示強制移除。