如何控制服务的运行状态？如何切换不同的运行级别？
ntsysv
- 仿图形交互界面，集中配置各种服务启动状态
--level 35：同时对指定运行级别中的服务进行管理，不加仅管理当前运行级别中的服务。
[root@localhost ~]# ntsysv --level 35
systemctl
- systemctl {选项} name.servive
start：启动stop：停止
[root@localhost ~]# systemctl start httpd.service [root@localhost ~]# systemctl stop httpd.service
restart：重启，先停止，再启动reload：重新加载配置文件，不会完全停止和启动服务
[root@localhost ~]# systemctl restart httpd.service [root@localhost ~]# systemctl reload httpd.service
status：状态is-active：是否启动成功is-failed：是否启动失败
[root@localhost ~]# systemctl status httpd.service ● httpd.service - The Apache HTTP Server Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled) Active: active (running) since Tue 2019-08-27 17:31:39 CST; 40s ago Docs: man:httpd(8) man:apachectl(8) Process: 8833 ExecReload=/usr/sbin/httpd $OPTIONS -k graceful (code=exited, status=0/SUCCESS) Main PID: 8821 (httpd) Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec" CGroup: /system.slice/httpd.service ├―8821 /usr/sbin/httpd -DFOREGROUND ├―8835 /usr/sbin/httpd -DFOREGROUND ├―8836 /usr/sbin/httpd -DFOREGROUND ├―8837 /usr/sbin/httpd -DFOREGROUND ├―8838 /usr/sbin/httpd -DFOREGROUND └―8839 /usr/sbin/httpd -DFOREGROUND Aug 27 17:31:39 localhost.localdomain systemd[1]: Starting The Apache HTTP Server... Aug 27 17:31:39 localhost.localdomain httpd[8821]: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using localhost.l...s message Aug 27 17:31:39 localhost.localdomain systemd[1]: Started The Apache HTTP Server. Aug 27 17:31:45 localhost.localdomain httpd[8833]: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using localhost.l...s message Aug 27 17:31:45 localhost.localdomain systemd[1]: Reloaded The Apache HTTP Server. Hint: Some lines were ellipsized, use -l to show in full.
[root@localhost ~]# systemctl is-active httpd.service active [root@localhost ~]# systemctl is-failed httpd.service active
enable：开机自启disable：关闭开机自启is-enabled：是否开机自启
[root@localhost ~]# systemctl enable httpd.service Created symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service. [root@localhost ~]# systemctl disable httpd.service Removed symlink /etc/systemd/system/multi-user.target.wants/httpd.service. [root@localhost ~]# systemctl is-enabled httpd.service disabled
list-dependencies：查看依赖关系
[root@localhost ~]# systemctl list-dependencies httpd.service httpd.service ● ├―-.mount ● ├―system.slice ● └―basic.target ● ├―microcode.service ● ├―rhel-autorelabel-mark.service ● ├―rhel-autorelabel.service ● ├―rhel-configure.service ● ├―rhel-dmesg.service ● ├―rhel-loadmodules.service ● ├―selinux-policy-migrate-local-changes@targeted.service ● ├―paths.target ● ├―slices.target ● │ ├―-.slice ● │ └―system.slice ● ├―sockets.target ● │ ├―dbus.socket ● │ ├―dm-event.socket ● │ ├―systemd-initctl.socket ● │ ├―systemd-journald.socket ● │ ├―systemd-shutdownd.socket ● │ ├―systemd-udevd-control.socket ● │ └―systemd-udevd-kernel.socket ● ├―sysinit.target ● │ ├―dev-hugepages.mount ● │ ├―dev-mqueue.mount ● │ ├―kmod-static-nodes.service ● │ ├―lvm2-lvmetad.socket ● │ ├―lvm2-lvmpolld.socket ● │ ├―lvm2-monitor.service ● │ ├―plymouth-read-write.service ● │ ├―plymouth-start.service ● │ ├―proc-sys-fs-binfmt_misc.automount ● │ ├―sys-fs-fuse-connections.mount ● │ ├―sys-kernel-config.mount ● │ ├―sys-kernel-debug.mount ● │ ├―systemd-ask-password-console.path ● │ ├―systemd-binfmt.service ● │ ├―systemd-firstboot.service ● │ ├―systemd-hwdb-update.service ● │ ├―systemd-journal-catalog-update.service ● │ ├―systemd-journal-flush.service ● │ ├―systemd-journald.service ● │ ├―systemd-machine-id-commit.service ● │ ├―systemd-modules-load.service ● │ ├―systemd-random-seed.service ● │ ├―systemd-sysctl.service ● │ ├―systemd-tmpfiles-setup-dev.service ● │ ├―systemd-tmpfiles-setup.service ● │ ├―systemd-udev-trigger.service ● │ ├―systemd-udevd.service ● │ ├―systemd-update-done.service ● │ ├―systemd-update-utmp.service ● │ ├―systemd-vconsole-setup.service ● │ ├―cryptsetup.target ● │ ├―local-fs.target ● │ │ ├―-.mount ● │ │ ├―boot.mount ● │ │ ├―rhel-import-state.service ● │ │ ├―rhel-readonly.service ● │ │ └―systemd-remount-fs.service ● │ └―swap.target ● │ └―dev-mapper-centos\x2dswap.swap ● └―timers.target ● └―systemd-tmpfiles-clean.timer
mask：屏蔽服务unmak：取消屏蔽
- 主要使用于相互冲突的服务，屏蔽后，不会被其他的
systemd单元启动，也无法被手动启动。例如iptables和firewalld就是互相冲突的。
[root@localhost ~]# systemctl mask firewalld.service Created symlink from /etc/systemd/system/firewalld.service to /dev/null. [root@localhost ~]# systemctl unmask firewalld.service Removed symlink /etc/systemd/system/firewalld.service.
runlevel
- 显示系统的运行级别
[root@localhost ~]# runlevel N 5
两种方法：
[root@localhost ~]# init 3
[root@localhost ~]# systemctl isolate multi-user.target
两种方法：
[root@localhost ~]# init 5
[root@localhost ~]# systemctl isolate graphical.target
1.查看默认启动target
[root@localhost ~]# systemctl get-default graphical.target
2.切换默认启动target，两种方法：
[root@localhost ~]# systemctl set-default multi-user.target Removed symlink /etc/systemd/system/default.target. Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.
[root@localhost ~]# ln -sf /lib/systemd/system/multi-user.target /etc/systemd/system/default.target
3.查看默认启动target
[root@localhost ~]# systemctl get-default multi-user.target
来源：博客园
作者：LinSenGeGe
链接：https://www.cnblogs.com/llife/p/11419983.html