遇到這種情況 , 開機延遲 , 可以用下面的辦法來查看 , 尋找到問題的源頭 , 來看看到的是怎么回事
[root@DaMoWang ~]# dmesg |grep udev #顯示系統的啟動信息 , 從中過濾udev [ 1.088863] systemd[1]: Listening on udev Control Socket. [ 1.088869] systemd[1]: Starting udev Control Socket. [ 1.088889] systemd[1]: Listening on udev Kernel Socket. [ 1.088893] systemd[1]: Starting udev Kernel Socket. [root@DaMoWang ~]# journalctl -k |grep udev #查看系統本次啟動的日志 , 從中過濾udev 7月 18 23:41:55 DaMoWang.localdomain systemd[1]: Listening on udev Control Socket. 7月 18 23:41:55 DaMoWang.localdomain systemd[1]: Starting udev Control Socket. 7月 18 23:41:55 DaMoWang.localdomain systemd[1]: Listening on udev Kernel Socket. 7月 18 23:41:55 DaMoWang.localdomain systemd[1]: Starting udev Kernel Socket.
這看不出有什么問題 , 下面來一項一項的找 , 看看到底等待的是哪個服務
[root@DaMoWang ~]# systemd-analyze blame #查看每個服務的啟動耗時 2min 586ms systemd-udev-settle.service 30.258s NetworkManager-wait-online.service 18.640s mysqld.service 14.771s tuned.service 12.301s named.service 11.617s postfix.service 11.201s polkit.service 10.604s ModemManager.service 10.135s dev-mapper-centos\x2droot.device 9.747s lvm2-monitor.service 8.636s systemd-logind.service 8.626s rpcbind.service 8.621s sysstat.service 8.589s gssproxy.service 8.588s named-setup-rndc.service 8.495s avahi-daemon.service 8.477s rhel-dmesg.service 7.612s httpd.service 6.934s chronyd.service 6.524s abrt-ccpp.service 5.783s vdo.service 5.039s network.service 3.982s auditd.service 3.306s boot.mount 3.027s systemd-tmpfiles-setup-dev.service 2.927s NetworkManager.service 2.670s systemd-udevd.service 2.292s lvm2-pvscan@8:2.service 2.272s rhel-readonly.service 2.019s lvm2-pvscan@8:33.service 1.797s lvm2-pvscan@8:65.service 1.788s dmraid-activation.service 1.761s lvm2-pvscan@8:49.service 1.679s lvm2-pvscan@8:17.service 1.462s sshd.service 1.327s rhel-domainname.service 1.267s plymouth-read-write.service 1.213s systemd-rfkill@rfkill0.service 1.212s rsyslog.service 880ms systemd-tmpfiles-setup.service 817ms dev-hugepages.mount 761ms systemd-remount-fs.service 759ms sys-kernel-debug.mount 758ms dev-mqueue.mount 696ms nfs-config.service 686ms rhel-import-state.service 644ms kmod-static-nodes.service 585ms systemd-journald.service 488ms systemd-user-sessions.service #下面還有很多服務 , 不過不需要看 , 只需要找到時間最長的那個服務就可以了
通過運行 systemd 分析，發現 systemd-udev-setle.service 是造成延遲的原因
[root@DaMoWang ~]# systemctl mask systemd-udev-settle #屏蔽掉這個服務 Created symlink from /etc/systemd/system/systemd-udev-settle.service to /dev/null.