一、设置crond.service服务为开机自启动

步骤1：查看crond.serivce服务的自启动状态

[root@test_jenkins ~]# [root@test_jenkins ~]# systemctl is-enabled crond.servicedisabled[root@test_jenkins ~]# [root@test_jenkins ~]#

此时crond.serivce的自启动状态为disabled

步骤2：开启crond.serivce服务自启动

[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl enable crond.serviceCreated symlink from /etc/systemd/system/multi-user.target.wants/crond.service to /usr/lib/systemd/system/crond.service.[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl is-enabled crond.serviceenabled[root@test_jenkins ~]#[root@test_jenkins ~]# [root@test_jenkins ~]# systemctl list-unit-files | grep enableabrt-ccpp.service                             enabled abrt-oops.service                             enabled abrt-vmcore.service                           enabled abrt-xorg.service                             enabled abrtd.service                                 enabled auditd.service                                enabled autovt@.service                               enabled crond.service                                 enabled dbus-org.freedesktop.NetworkManager.service   enabled dbus-org.freedesktop.nm-dispatcher.service    enabled getty@.service                                enabled irqbalance.service                            enabled lvm2-monitor.service                          enabled microcode.service                             enabled NetworkManager-dispatcher.service             enabled NetworkManager.service                        enabled ntpd.service                                  enabled postfix.service                               enabled rsyslog.service                               enabled snmpd.service                                 enabled sshd.service                                  enabled systemd-readahead-collect.service             enabled systemd-readahead-drop.service                enabled systemd-readahead-replay.service              enabled tuned.service                                 enabled xinetd.service                                enabled dm-event.socket                               enabled lvm2-lvmetad.socket                           enabled lvm2-lvmpolld.socket                          enabled pcscd.socket                                  enabled telnet.socket                                 enabled default.target                                enabled multi-user.target                             enabled remote-fs.target                              enabled runlevel2.target                              enabled runlevel3.target                              enabled runlevel4.target                              enabled

此时crond.serivce的自启动状态为enabled

附：关闭crond.serivce的自启动状态

[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl disable crond.serviceRemoved symlink /etc/systemd/system/multi-user.target.wants/crond.service.[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl is-enabled crond.servicedisabled[root@test_jenkins ~]# [root@test_jenkins ~]#

二、开启和关闭crond.service服务

步骤1：查看crond.service的启动状态

[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl status crond.service● crond.service - Command Scheduler   Loaded: loaded (/usr/lib/systemd/system/crond.service; enabled; vendor preset: enabled)   Active: inactive (dead) since 六 2017-07-29 14:19:12 CST; 5s ago  Process: 805 ExecStart=/usr/sbin/crond -n $CRONDARGS (code=exited, status=0/SUCCESS) Main PID: 805 (code=exited, status=0/SUCCESS)7月 28 14:23:31 test_jenkins systemd[1]: Started Command Scheduler.7月 28 14:23:31 test_jenkins systemd[1]: Starting Command Scheduler...7月 28 14:23:31 test_jenkins crond[805]: (CRON) INFO (RANDOM_DELAY will be scaled with factor 84% if used.)7月 28 14:23:31 test_jenkins crond[805]: (CRON) INFO (running with inotify support)7月 29 14:19:12 test_jenkins systemd[1]: Stopping Command Scheduler...7月 29 14:19:12 test_jenkins systemd[1]: Stopped Command Scheduler.[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]#

此处显示crond.service的启动状态为dead

步骤2：开启服务

[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl start crond.service[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]#

再次查看crond.service的启动状态

[root@test_jenkins ~]# [root@test_jenkins ~]# [root@test_jenkins ~]# systemctl status crond.service● crond.service - Command Scheduler   Loaded: loaded (/usr/lib/systemd/system/crond.service; enabled; vendor preset: enabled)   Active: active (running) since 六 2017-07-29 14:19:56 CST; 3s ago Main PID: 8465 (crond)   CGroup: /system.slice/crond.service           └─8465 /usr/sbin/crond -n7月 29 14:19:56 test_jenkins systemd[1]: Started Command Scheduler.7月 29 14:19:56 test_jenkins systemd[1]: Starting Command Scheduler...7月 29 14:19:56 test_jenkins crond[8465]: (CRON) INFO (RANDOM_DELAY will be scaled with factor 44% if used.)7月 29 14:19:56 test_jenkins crond[8465]: (CRON) INFO (running with inotify support)7月 29 14:19:56 test_jenkins crond[8465]: (CRON) INFO (@reboot jobs will be run at computer's startup.)[root@test_jenkins ~]# [root@test_jenkins ~]#

此处显示crond.service的启动状态为running