自从安装了CentOS7系统，它的启动时间常常要三分钟以上，实在忍不了。
以下是CentOS7系统的启动记录片断：
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，黄色背景部分的操作，极其耗时，这两句的用时将近两分钟。
后来，谷歌查之，发现这个是CentOS7系统下常见的bug，果然遇到问题不能问百度，简直是白白浪费生命！
解决办法也很简单粗暴，屏蔽掉这个系统服务即可：
systemctl mask systemd-udev-settle
现在，开机时间从先前的2-3分钟提高到1分以内，总算正常了。
参考链接：
https://bbs.archlinux.org/viewtopic.php?id=189106
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=786942