最近遇到了两起 X11 下客户端报 Maximum number of clients reached 的错误，并且无法连接到 Xorg。

搜到了一个排查方法，执行

sudo ss -x src "*/tmp/.X11-unix/*" | grep -Eo "[0-9]+\s*$" | while read port
do
  sudo ss -p -x | grep -w $port | grep -v X11-unix
done | grep -Eo '".+"' | sort | uniq -c | sort -rn

这将列出每个进程及其打开的 X 连接数，按连接数降序排列。

13 "dde-session-dae"
 5 "fcitx"
 3 "kwin_x11"
 3 "kglobalaccel5"
 2 "cpis-panel-serv"
 1 "uos-activator"
 1 "startdde"

https://snapoverflow.com/ubuntu/question/4499/how-can-i-diagnose-debug-maximum-number-of-clients-reached-x-errors/