systemctl命令的使用
管理服务
我们一起来看一下在服务管理方面systemctl这个工具如何使用
[root@localhost ~]# systemctl start servername
start 启动服务
stop 停止服务
restart 重启服务(没启动的服务会启动)
try-restart 只重启正在运行的服务(没有运行则不启动)
reload 重载配置文件(修改完服务的配置文件后使用)
status 检查服务状态
is-active 检查服务是否已经启动
enable 设置服务开机时启动
disable 设置服务开机时不启动
is-enabled 查看服务是否开机自动启动
mask 屏蔽一个服务
unmask 取消屏蔽
[root@localhost ~]# systemctl status httpd
● httpd.service - The Apache HTTP Server 服务名称
Loaded: loaded 加载到内存中;error加载失败;bad-setting无法理解单元配置文件中的设置;masked被屏蔽 (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled) 服务开机时是否启动 enabled为启动;disabled为不启动
Active: active (running) since Mon 2019-11-18 15:56:46 CST; 1h 11min ago 服务当前的状态,active(running)为运行;active(exited)运行一次就退出了;active(waiting)运行中,但是再等待其它程序结束才能继续;inactive(dead)为没有运行;activating为启动中,deactivating停止中;failed启动失败
Docs: man:httpd.service(8) 服务的帮助文档
Main PID: 57779 (httpd) 服务的主进程号
Status: "Running, listening on: port 80" 额外的状态信息
Tasks: 213 (limit: 24882) 任务数量,含进程+线程
Memory: 22.4M 当前占用的内存
CGroup: /system.slice/httpd.service
├─57779 /usr/sbin/httpd -DFOREGROUND
├─57780 /usr/sbin/httpd -DFOREGROUND
├─57781 /usr/sbin/httpd -DFOREGROUND
├─57782 /usr/sbin/httpd -DFOREGROUND
└─57783 /usr/sbin/httpd -DFOREGROUND
Control Groups额外信息
11月 18 15:56:46 localhost.localdomain systemd[1]: Starting The Apache HTTP Server...
11月 18 15:56:46 localhost.localdomain httpd[57779]: AH00558: httpd: Could not reliably determ>
11月 18 15:56:46 localhost.localdomain httpd[57779]: Server configured, listening on: port 80
11月 18 15:56:46 localhost.localdomain systemd[1]: Started The Apache HTTP Server.
例:
[root@localhost ~]# systemctl is-active atd
inactive
[root@localhost ~]# systemctl start atd
[root@localhost ~]# systemctl status atd
● atd.service - Job spooling tools
Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled)
Active: active (running) since Mon 2019-11-18 18:36:26 CST; 7s ago
Main PID: 60620 (atd)
Tasks: 1 (limit: 24882)
Memory: 504.0K
CGroup: /system.slice/atd.service
└─60620 /usr/sbin/atd -f
11月 18 18:36:26 localhost.localdomain systemd[1]: Started Job spooling tools.
[root@localhost ~]# systemctl stop atd
[root@localhost ~]# systemctl status atd
● atd.service - Job spooling tools
Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled)
Active: inactive (dead) since Mon 2019-11-18 18:36:43 CST; 6s ago
Process: 60620 ExecStart=/usr/sbin/atd -f $OPTS (code=exited, status=0/SUCCESS)
Main PID: 60620 (code=exited, status=0/SUCCESS)
11月 18 18:36:26 localhost.localdomain systemd[1]: Started Job spooling tools.
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopping Job spooling tools...
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopped Job spooling tools.
[root@localhost ~]# systemctl is-enabled atd
enabled
[root@localhost ~]# systemctl disable atd
Removed /etc/systemd/system/multi-user.target.wants/atd.service.
[root@localhost ~]# systemctl is-enabled atd
disabled
[root@localhost ~]# systemctl enable atd
Created symlink /etc/systemd/system/multi-user.target.wants/atd.service → /usr/lib/systemd/system/atd.service.
[root@localhost ~]# systemctl is-enabled atd
enabled
[root@localhost ~]# systemctl stop atd
[root@localhost ~]# systemctl mask atd
Created symlink /etc/systemd/system/atd.service → /dev/null.
[root@localhost ~]# systemctl status atd
● atd.service
Loaded: masked (Reason: Unit atd.service is masked.)
Active: inactive (dead)
11月 05 18:12:41 localhost.localdomain systemd[1]: Started Job spooling tools.
11月 18 18:34:15 localhost.localdomain systemd[1]: Stopping Job spooling tools...
11月 18 18:34:15 localhost.localdomain systemd[1]: Stopped Job spooling tools.
11月 18 18:36:26 localhost.localdomain systemd[1]: Started Job spooling tools.
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopping Job spooling tools...
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopped Job spooling tools.
[root@localhost ~]# systemctl unmask atd
Removed /etc/systemd/system/atd.service.
[root@localhost ~]# systemctl status atd
● atd.service - Job spooling tools
Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled)
Active: inactive (dead)
11月 05 18:12:41 localhost.localdomain systemd[1]: Started Job spooling tools.
11月 18 18:34:15 localhost.localdomain systemd[1]: Stopping Job spooling tools...
11月 18 18:34:15 localhost.localdomain systemd[1]: Stopped Job spooling tools.
11月 18 18:36:26 localhost.localdomain systemd[1]: Started Job spooling tools.
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopping Job spooling tools...
11月 18 18:36:43 localhost.localdomain systemd[1]: Stopped Job spooling tools
查看服务
[root@localhost ~]#systemctl command --type=xxx --all
list-units 查看所有加载到内存中的单元
list-unit-files 查看系统中所有安装的单元文件(存放在/usr/lib/systemd/system)的启用状态
--type=xxx 单元类型
--all 列出系统中所有加载的,不管状态为何
[root@localhost ~]# systemctl
UNIT LOAD ACTIVE SUB DESCRIPTION
sys.. loaded active plugged /sys.....
sys.. loaded active plugged /sys.....
sys.. loaded active plugged /sys.....
sys.. loaded active plugged /sys.....
sys.. loaded active plugged /sys.....
sys.. loaded active plugged /sys.....
UNIT: 单元名称
LOAD: 是否被加载
ACTIVE: 高优先级单元状态,与SUB结合就是使用status查看的状态
SUB: 低优先级单元状态
DESCRIPTION:简介
[root@localhost ~]# systemctl list-unit-files
UNIT FILE STATE
proc... static
-.mount generated
boot.mount generated
dev-hugepages.mount static
dev-mqueue.mount static
proc-fs-nfsd.mount static
proc-... static
sys-f... static
sys-... static
sys-ke.. static
tmp.mount static
var-lib.. static
var-lib.. static
cups.path.. enabled
systemd.. static
查看指定类型的服务
[root@localhost ~]# systemctl --type target --all
UNIT LOAD ACTIVE SUB DESCRIPTION
basic.target loaded active active Basic System
bluetooth.target loaded active active Bluetooth
cryptsetup.target loaded active active Local...
● dbus.target not-found inactive dead dbus.target
[root@localhost ~]# systemctl --type=target --all
UNIT LOAD ACTIVE SUB DESCRIPTION
basic.target loaded active active Basic System
bluetooth.target loaded active active Bluetooth
cryptsetup.target loaded active active Local...
● dbus.target not-found inactive dead dbus.target
[root@localhost ~]# systemctl list-units --type=target --all
UNIT LOAD ACTIVE SUB DESCRIPTION
basic.target loaded active active Basic System
bluetooth.target loaded active active Bluetooth
cryptsetup.target loaded active active Local...
● dbus.target not-found inactive dead dbus.target
使用systemctl切换运行级别
[root@localhost ~]# systemctl list-units --type target --all
UNIT LOAD ACTIVE SUB DESCRIPTION
basic.target loaded active active Basic System
bluetooth.target loaded inactive dead Bluetooth
cryptsetup.target loaded active active Local ..
● dbus.target not-found inactive dead dbus.target
emergency.target loaded inactive dead Emergency Mode
getty-pre.target loaded inactive dead Login..
getty.target loaded active active Login Prompts
graphical.target loaded inactive dead Graphica..Interface
常用的target
graphical.target:图形模式
multi-user.target:字符模式
rescue.target:救援模式
emergency.target:紧急模式,无法进入到救援模式时使用
shutdown.target:关机
[root@localhost ~]# systemctl get-default 查看默认运行级别
graphical.target
[root@localhost ~]# systemctl set-default multi-user.target 设置
Removed /etc/systemd/system/default.target.
Created symlink /etc/systemd/system/default.target → /usr/lib/systemd/system/multi-user.target.
[root@localhost ~]# systemctl isolate multi-user.target 切换
除了可以使用上述方法设置和查看之外 系统还给我们提供了几个简单的命令,方便操作
[root@localhost ~]# systemctl poweroff 关机
[root@localhost ~]# systemctl reboot 重启
[root@localhost ~]# systemctl suspend 挂起
[root@localhost ~]# systemctl hibernate 休眠
[root@localhost ~]# systemctl rescue 进入到救援模式
[root@localhost ~]# systemctl emergency 进入到紧急模式
查看服务之间的依赖关系
[root@localhost ~]# systemctl list-dependencies multi-user.target
查看multi-user.target依赖谁
multi-user.target
● ├─atd.service
.
.
.
● ├─basic.target
● │ ├─-.mount
● │ ├─microcode.service
● │ ├─paths.target
● │ ├─slices.target
● │ │ ├─-.slice
● │ │ └─system.slice
● │ ├─sockets.target
● │ │ ├─avahi-daemon.socket
.
.
.
[root@localhost ~]# systemctl list-dependencies multi-user.target --reverse 查看谁依赖multi-user.target
multi-user.target
● └─graphical.target
小结
systemctl命令的使用
服务的启动
服务的停止
服务的状态
服务的自启动
systemctl查看服务信息
运行级别切换及常用的target单元
sytemctl的额外功能
依赖关系的查看
这些内容,包括回显内容都是重点,一定要熟记,都是以后要经常用到的命令。
难点:命令较多,建议在理解的基础上进行记忆,更容易一些