自從安裝了CentOS7系統，它的啟動時間常常要三分鍾以上，實在忍不了。
以下是CentOS7系統的啟動記錄片斷：
May 18 13:04:05 DESKTOP-23V3CHU kernel: XFS (dm-2): Mounting V5 Filesystem May 18 13:04:05 DESKTOP-23V3CHU kernel: XFS (dm-2): Ending clean mount May 18 13:04:05 DESKTOP-23V3CHU systemd: Mounted /home. May 18 13:05:02 DESKTOP-23V3CHU systemd-udevd: worker [555] /devices/platform/i8042/serio1/input/input6/event6 is taking a long time May 18 13:05:58 DESKTOP-23V3CHU systemd: systemd-udev-settle.service: main process exited, code=exited, status=1/FAILURE May 18 13:05:58 DESKTOP-23V3CHU systemd: Failed to start udev Wait for Complete Device Initialization. May 18 13:05:58 DESKTOP-23V3CHU systemd: Unit systemd-udev-settle.service entered failed state. May 18 13:05:58 DESKTOP-23V3CHU systemd: systemd-udev-settle.service failed. May 18 13:05:58 DESKTOP-23V3CHU systemd: Starting Activation of DM RAID sets... May 18 13:05:59 DESKTOP-23V3CHU systemd: Started Activation of DM RAID sets.
其中，黃色背景部分的操作，極其耗時，這兩句的用時將近兩分鍾。
后來，谷歌查之，發現這個是CentOS7系統下常見的bug，果然遇到問題不能問百度，簡直是白白浪費生命！
解決辦法也很簡單粗暴，屏蔽掉這個系統服務即可：
systemctl mask systemd-udev-settle
現在，開機時間從先前的2-3分鍾提高到1分以內，總算正常了。
參考鏈接：
https://bbs.archlinux.org/viewtopic.php?id=189106
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=786942