linux命令学习之：systemctl

　　systemctl命令是系统服务管理器指令，主要负责控制systemd系统和服务管理器，它实际上将 service 和 chkconfig 这两个命令组合到一起。

　　CentOS 7.x开始，CentOS开始使用systemd服务来代替daemon，原来管理系统启动和管理系统服务的相关命令全部由systemctl命令来代替。

　　Systemd是一个系统管理守护进程、工具和库的集合，用于取代System V初始进程。Systemd的功能是用于集中管理和配置类UNIX系统。

　　在Linux生态系统中，Systemd被部署到了大多数的标准Linux发行版中，只有为数不多的几个发行版尚未部署。Systemd通常是所有其它守护进程的父进程，但并非全是如此。

1、原来的 service 命令与 systemctl 命令对比

daemon命令	systemctl命令	说明
service [服务] start	systemctl start [unit type]	启动服务
service [服务] stop	systemctl stop [unit type]	停止服务
service [服务] restart	systemctl restart [unit type]	重启服务

此外还是二个systemctl参数没有与service命令参数对应

status：参数来查看服务运行情况
reload：重新加载服务，加载更新后的配置文件（并不是所有服务都支持这个参数，比如network.service）

　　示例：

#启动网络服务
systemctl start network.service

#停止网络服务
systemctl stop network.service

#重启网络服务
systemctl restart network.service

#查看网络服务状态
systemctl status network.serivce

2、原来的chkconfig 命令与 systemctl 命令对比

daemon命令	systemctl命令	说明
chkconfig [服务] on	systemctl enable [unit type]	设置服务开机启动
chkconfig [服务] off	systemctl disable [unit type]	设备服务禁止开机启动

　　示例：

#停止cup电源管理服务
systemctl stop cups.service

#禁止cups服务开机启动
systemctl disable cups.service

#查看cups服务状态
systemctl status cups.service

#重新设置cups服务开机启动
systemctl enable cups.service

3、查看系统上上所有的服务

　　命令格式：systemctl [command] [–type=TYPE] [–all]

　　参数详解：

　　command - list-units：依据unit列出所有启动的unit。加上 –all 才会列出没启动的unit; - list-unit-files:依据/usr/lib/systemd/system/ 内的启动文件，列出启动文件列表

–type=TYPE - 为unit type, 主要有service, socket, target

　　应用举例：

systemctl命令	说明
systemctl	列出所有的系统服务
systemctl list-units	列出所有启动unit
systemctl list-unit-files	列出所有启动文件
systemctl list-units –type=service –all	列出所有service类型的unit
systemctl list-units –type=service –all grep cpu	列出 cpu电源管理机制的服务
systemctl list-units –type=target –all	列出所有target

4、systemctl特殊的用法

systemctl命令	说明
systemctl is-active [unit type]	查看服务是否运行
systemctl is-enable [unit type]	查看服务是否设置为开机启动
systemctl mask [unit type]	注销指定服务
systemctl unmask [unit type]	取消注销指定服务

　　应用举例：

#查看网络服务是否启动
systemctl is-active network.service

#检查网络服务是否设置为开机启动
systemctl is-enable network.service

#停止cups服务
systemctl stop cups.service

#注销cups服务
systemctl mask cups.service

#查看cups服务状态
systemctl status cups.service

#取消注销cups服务
systemctl unmask cups.service

5、常用示例：

Systemctl基础、体验

1. 检查系统中是否安装有systemctl并确定当前安装的版本

[root@CTU1000094955 ~]# systemctl --version
systemd 219
+PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID +ELFUTILS +KMOD +IDN

　　上例中很清楚地表明，我们安装了219版本的systemctl。

2. 检查systemd和systemctl的二进制文件和库文件的安装位置

[root@CTU1000094955 ~]# whereis systemd
systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz
[root@CTU1000094955 ~]# whereis systemctl
systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz

3. 检查systemd是否运行

[root@CTU1000094955 ~]# ps -eaf | grep [s]ystemd
root          1      0  0 16:15 ?        00:00:04 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
root        631      1  0 16:15 ?        00:00:24 /usr/lib/systemd/systemd-journald
root        661      1  0 16:15 ?        00:00:00 /usr/lib/systemd/systemd-udevd
dbus        813      1  0 16:15 ?        00:00:02 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
root        841      1  0 16:15 ?        00:00:00 /usr/lib/systemd/systemd-logind

　　注意：systemd是作为父进程（PID=1）运行的。在上面带（-e）参数的ps命令输出中，选择所有进程，（-a）选择除会话前导外的所有进程，并使用（-f）参数输出完整格式列表（即 -eaf）。

　　也请注意上例中后随的方括号和例子中剩余部分。方括号表达式是grep的字符类表达式的一部分。

4. 分析systemd启动进程

[root@CTU1000094955 ~]# systemd-analyze
Startup finished in 743ms (kernel) + 6.959s (initrd) + 17.696s (userspace) = 25.399s

5. 分析启动时各个进程花费的时间

[root@CTU1000094955 ~]# systemd-analyze blame
         11.859s dev-xvda1.device
          5.670s NetworkManager-wait-online.service
          4.610s plymouth-quit-wait.service
          3.757s systemd-udev-settle.service
          3.078s kdump.service
          2.257s mysql.service
          1.451s libvirtd.service
          1.228s postfix.service
           751ms uvp-monitor.service
           675ms spesserviced.service
           675ms messageserviced.service
           660ms tuned.service
           586ms network.service
           525ms accounts-daemon.service
           467ms NetworkManager.service
           457ms systemd-udevd.service
           416ms abrt-ccpp.service
           397ms firewalld.service
           365ms ModemManager.service

6. 分析启动时的关键链

[root@CTU1000094955 ~]# systemd-analyze critical-chain
The time after the unit is active or started is printed after the "@" character.
The time the unit takes to start is printed after the "+" character.

graphical.target @17.682s
?..multi-user.target @17.682s
  ?..getty.target @17.682s
    ?..serial-getty@hvc0.service @17.681s
      ?..systemd-user-sessions.service @12.929s +18ms
        ?..remote-fs.target @12.921s
          ?..remote-fs-pre.target @12.921s
            ?..iscsi-shutdown.service @12.907s +12ms
              ?..network.target @12.900s
                ?..network.service @12.311s +586ms
                  ?..NetworkManager.service @6.166s +467ms
                    ?..basic.target @5.903s
                      ?..sockets.target @5.903s
                        ?..rpcbind.socket @5.903s
                          ?..sysinit.target @5.895s
                            ?..systemd-update-utmp.service @5.877s +16ms
                              ?..auditd.service @5.738s +135ms
                                ?..systemd-tmpfiles-setup.service @5.661s +73ms
                                  ?..rhel-import-state.service @5.526s +134ms
                                    ?..local-fs.target @5.525s
                                      ?..run-user-0.mount @14.041s
                                        ?..local-fs-pre.target @1.615s
                                          ?..systemd-tmpfiles-setup-dev.service @
                                            ?..kmod-static-nodes.service @1.473s 
                                              ?..systemd-journald.socket
                                                ?..-.slice

　　重要：Systemctl接受服务（.service），挂载点（.mount），套接口（.socket）和设备（.device）作为单元。

7. 列出所有可用单元

[root@CTU1000094955 ~]# systemctl list-unit-files
UNIT FILE                                   STATE   
proc-sys-fs-binfmt_misc.automount           static  
dev-hugepages.mount                         static  
dev-mqueue.mount                            static  
proc-fs-nfsd.mount                          static  
proc-sys-fs-binfmt_misc.mount               static  
sys-fs-fuse-connections.mount               static  
sys-kernel-config.mount                     static  
sys-kernel-debug.mount                      static  
tmp.mount                                   disabled
var-lib-nfs-rpc_pipefs.mount                static  
brandbot.path                               disabled
cups.path                                   enabled 
systemd-ask-password-console.path           static

8. 列出所有运行中单元

[root@CTU1000094955 ~]# systemctl list-units
  UNIT                                                                               LOAD   ACTIVE SUB       DESCRIPTION
  proc-sys-fs-binfmt_misc.automount                                                  loaded active waiting   Arbitrary Executable File Formats File System Automount Point
  sys-devices-pci0000:00-0000:00:01.1-ata2-host1-target1:0:1-1:0:1:0-block-sr0.device loaded active plugged   QEMU_DVD-ROM
  sys-devices-platform-serial8250-tty-ttyS2.device                                   loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS2
  sys-devices-platform-serial8250-tty-ttyS3.device                                   loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
  sys-devices-pnp0-00:08-tty-ttyS0.device                                            loaded active plugged   /sys/devices/pnp0/00:08/tty/ttyS0
  sys-devices-pnp0-00:09-tty-ttyS1.device                                            loaded active plugged   /sys/devices/pnp0/00:09/tty/ttyS1
  sys-devices-vbd\x2d51712-block-xvda-xvda1.device                                   loaded active plugged   /sys/devices/vbd-51712/block/xvda/xvda1
  sys-devices-vbd\x2d51712-block-xvda-xvda2.device                                   loaded active plugged   /sys/devices/vbd-51712/block/xvda/xvda2
  sys-devices-vbd\x2d51712-block-xvda.device                                         loaded active plugged   /sys/devices/vbd-51712/block/xvda
  sys-devices-vbd\x2d51776-block-xvde.device                                         loaded active plugged   LVM PV I2rhCm-www3-J79i-r3ei-1XCb-a1qS-3OWSg9 on /dev/xvde
  sys-devices-vif\x2d0-net-eth0.device                                               loaded active plugged   /sys/devices/vif-0/net/eth0

9. 列出所有失败单元

[root@CTU1000094955 ~]# systemctl --failed
  UNIT              LOAD   ACTIVE SUB    DESCRIPTION
?.bluetooth.service loaded failed failed Bluetooth service
?.rc-local.service  loaded failed failed /etc/rc.d/rc.local Compatibility

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

2 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

10. 检查某个单元（如 cron.service）是否启用

[root@CTU1000094955 ~]# systemctl is-enabled firewalld.service
disabled

11. 检查某个单元或服务是否运行

[root@CTU1000094955 ~]# systemctl status firewalld.service
?.firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
   Active: active (running) since Sat 2017-11-25 16:20:44 CST; 1h 29min ago
 Main PID: 7677 (firewalld)
   CGroup: /system.slice/firewalld.service
           ?..7677 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Nov 25 16:20:43 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 16:20:44 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.

使用Systemctl控制并管理服务

12. 列出所有服务（包括启用的和禁用的）

[root@CTU1000094955 ~]# systemctl list-unit-files --type=service
UNIT FILE                                   STATE   
abrt-ccpp.service                           enabled 
abrt-oops.service                           enabled 
abrt-pstoreoops.service                     disabled
abrt-vmcore.service                         enabled 
abrt-xorg.service                           enabled 
abrtd.service                               enabled 
accounts-daemon.service                     enabled 
alsa-restore.service                        static  
alsa-state.service                          static  
alsa-store.service                          static  
anaconda-direct.service                     static  
anaconda-nm-config.service                  static  
anaconda-noshell.service                    static  
anaconda-shell@.service                     static

13. Linux中如何启动、重启、停止、重载服务以及检查服务（如 firewalld.service）状态

[root@CTU1000094955 ~]# systemctl start httpd.service
Failed to start httpd.service: Unit httpd.service failed to load: No such file or directory.
[root@CTU1000094955 ~]# systemctl start firewalld.service
[root@CTU1000094955 ~]# systemctl restart firewalld.service
[root@CTU1000094955 ~]# systemctl stop firewalld.service
[root@CTU1000094955 ~]# systemctl reload firewalld.service
Job for firewalld.service invalid.
[root@CTU1000094955 ~]# systemctl status firewalld.service
?.firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
   Active: inactive (dead)

Nov 25 16:18:11 CTU1000094955 systemd[1]: Stopped firewalld - dynamic firewall daemon.
Nov 25 16:20:43 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 16:20:44 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:52:25 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:52:38 CTU1000094955 systemd[1]: Stopping firewalld - dynamic firewall daemon...
Nov 25 17:52:40 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 17:52:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:52:53 CTU1000094955 systemd[1]: Stopping firewalld - dynamic firewall daemon...
Nov 25 17:52:55 CTU1000094955 systemd[1]: Stopped firewalld - dynamic firewall daemon.
Nov 25 17:53:07 CTU1000094955 systemd[1]: Unit firewalld.service cannot be reloaded because it is inactive.
[root@CTU1000094955 ~]# systemctl restart firewalld.service
[root@CTU1000094955 ~]# systemctl reload firewalld.service
[root@CTU1000094955 ~]# systemctl status firewalld.service
?.firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
   Active: active (running) since Sat 2017-11-25 17:53:40 CST; 8s ago
  Process: 31721 ExecReload=/bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
 Main PID: 31008 (firewalld)
   CGroup: /system.slice/firewalld.service
           ?..31008 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.

　　注意：当我们使用systemctl的start，restart，stop和reload命令时，我们不会从终端获取到任何输出内容，只有status命令可以打印输出。

14. 如何激活服务并在启动时启用或禁用服务（即系统启动时自动启动服务）

[root@CTU1000094955 ~]# systemctl is-active firewalld.service
active
[root@CTU1000094955 ~]# systemctl enable firewalld.service
Created symlink from /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service to /usr/lib/systemd/system/firewalld.service.
Created symlink from /etc/systemd/system/basic.target.wants/firewalld.service to /usr/lib/systemd/system/firewalld.service.
[root@CTU1000094955 ~]# systemctl list-unit-files |grep firewall
firewalld.service                           enabled 
[root@CTU1000094955 ~]# systemctl status firewalld.service
?.firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2017-11-25 17:53:40 CST; 4min 6s ago
 Main PID: 31008 (firewalld)
   CGroup: /system.slice/firewalld.service
           ?..31008 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.
[root@CTU1000094955 ~]# systemctl disable firewalld.service
Removed symlink /etc/systemd/system/basic.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@CTU1000094955 ~]# systemctl list-unit-files |grep firewall
firewalld.service                           disabled

15. 如何屏蔽（让它不能启动）或显示服务（如 httpd.service）

[root@CTU1000094955 ~]# systemctl mask firewalld.service
Created symlink from /etc/systemd/system/firewalld.service to /dev/null.
[root@CTU1000094955 ~]# systemctl unmask firewalld.service
Removed symlink /etc/systemd/system/firewalld.service.

16. 使用systemctl命令杀死服务

[root@CTU1000094955 ~]# systemctl kill httpd
Failed to kill unit httpd.service: Unit httpd.service is not loaded.
[root@CTU1000094955 ~]# systemctl kill firewalld.service
[root@CTU1000094955 ~]# systemctl status firewalld.service
?.firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Sat 2017-11-25 18:05:17 CST; 7s ago
 Main PID: 31008 (code=exited, status=0/SUCCESS)

Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.

使用Systemctl控制并管理挂载点

17. 列出所有系统挂载点

[root@CTU1000094955 ~]# systemctl list-unit-files --type=mount
UNIT FILE                     STATE   
dev-hugepages.mount           static  
dev-mqueue.mount              static  
proc-fs-nfsd.mount            static  
proc-sys-fs-binfmt_misc.mount static  
sys-fs-fuse-connections.mount static  
sys-kernel-config.mount       static  
sys-kernel-debug.mount        static  
tmp.mount                     disabled
var-lib-nfs-rpc_pipefs.mount  static  

9 unit files listed.

18. 挂载、卸载、重新挂载、重载系统挂载点并检查系统中挂载点状态

[root@CTU1000094955 ~]# systemctl start tmp.mount
[root@CTU1000094955 ~]# systemctl stop tmp.mount
[root@CTU1000094955 ~]# systemctl reload tmp.mount
Job for tmp.mount invalid.
[root@CTU1000094955 ~]# systemctl status tmp.mount
?.tmp.mount - Temporary Directory
   Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled; vendor preset: disabled)
   Active: inactive (dead) since Sat 2017-11-25 18:09:06 CST; 25s ago
    Where: /tmp
     What: tmpfs
     Docs: man:hier(7)
           http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
  Process: 40649 ExecUnmount=/bin/umount /tmp -n (code=exited, status=0/SUCCESS)
  Process: 40271 ExecMount=/bin/mount tmpfs /tmp -n -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)

Nov 25 18:08:58 CTU1000094955 systemd[1]: Mounting Temporary Directory...
Nov 25 18:08:58 CTU1000094955 systemd[1]: Mounted Temporary Directory.
Nov 25 18:09:06 CTU1000094955 systemd[1]: Unmounting Temporary Directory...
Nov 25 18:09:06 CTU1000094955 systemd[1]: Unmounted Temporary Directory.
Nov 25 18:09:21 CTU1000094955 systemd[1]: Unit tmp.mount cannot be reloaded because it is inactive.
[root@CTU1000094955 ~]# systemctl restart tmp.mount
[root@CTU1000094955 ~]# systemctl status tmp.mount
?.tmp.mount - Temporary Directory
   Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled; vendor preset: disabled)
   Active: active (mounted) since Sat 2017-11-25 18:09:53 CST; 2s ago
    Where: /tmp
     What: tmpfs
     Docs: man:hier(7)
           http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
  Process: 40649 ExecUnmount=/bin/umount /tmp -n (code=exited, status=0/SUCCESS)
  Process: 41410 ExecMount=/bin/mount tmpfs /tmp -n -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)

Nov 25 18:09:53 CTU1000094955 systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
Nov 25 18:09:53 CTU1000094955 systemd[1]: Mounting Temporary Directory...
Nov 25 18:09:53 CTU1000094955 systemd[1]: Mounted Temporary Directory.
[root@CTU1000094955 ~]# systemctl reload tmp.mount

19. 在启动时激活、启用或禁用挂载点（系统启动时自动挂载）

[root@CTU1000094955 ~]# systemctl is-active tmp.mount
active
[root@CTU1000094955 ~]# systemctl disable tmp.mount
Removed symlink /etc/systemd/system/local-fs.target.wants/tmp.mount.
[root@CTU1000094955 ~]# systemctl is-active tmp.mount
active
[root@CTU1000094955 ~]# systemctl enable tmp.mount
Failed to execute operation: Access denied

20. 在Linux中屏蔽（让它不能启用）或可见挂载点

[root@CTU1000094955 ~]# systemctl mask tmp.mount
ln -s '/dev/null''/etc/systemd/system/tmp.mount'
[root@CTU1000094955 ~]# systemctl unmask tmp.mount
rm '/etc/systemd/system/tmp.mount'

使用Systemctl控制并管理套接口

21. 列出所有可用系统套接口

[root@CTU1000094955 ~]# systemctl list-unit-files --type=socket
UNIT FILE                    STATE   
avahi-daemon.socket          enabled 
cups.socket                  enabled 
dbus.socket                  static  
dm-event.socket              enabled 
iscsid.socket                enabled 
iscsiuio.socket              enabled 
libvirtd.socket              static  
lldpad.socket                disabled
lvm2-lvmetad.socket          enabled 
lvm2-lvmpolld.socket         enabled 
rpcbind.socket               enabled 
rsyncd.socket                disabled
sshd.socket                  disabled
syslog.socket                static  
systemd-initctl.socket       static  
systemd-journald.socket      static  
systemd-networkd.socket      disabled
systemd-shutdownd.socket     static  
systemd-udevd-control.socket static  
systemd-udevd-kernel.socket  static  
virtlockd.socket             disabled

21 unit files listed.

22. 在Linux中启动、重启、停止、重载套接口并检查其状态

[root@CTU1000094955 ~]# systemctl start sshd.socket
[root@CTU1000094955 ~]# systemctl restart sshd.socket
Failed to restart sshd.socket: Transaction contains conflicting jobs 'restart' and 'stop' for sshd-keygen.service. Probably contradicting requirement dependencies configured.
[root@CTU1000094955 ~]# systemctl status sshd.socket
?.sshd.socket - OpenSSH Server Socket
   Loaded: loaded (/usr/lib/systemd/system/sshd.socket; disabled; vendor preset: disabled)
   Active: active (listening) since Sat 2017-11-25 18:28:12 CST; 22s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
   Listen: [::]:22 (Stream)
 Accepted: 0; Connected: 0

Nov 25 18:28:12 CTU1000094955 systemd[1]: Listening on OpenSSH Server Socket.
Nov 25 18:28:12 CTU1000094955 systemd[1]: Starting OpenSSH Server Socket.
[root@CTU1000094955 ~]# systemctl stop sshd.socket
[root@CTU1000094955 ~]# systemctl reload sshd.socket
Failed to reload sshd.socket: Job type reload is not applicable for unit sshd.socket.
[root@CTU1000094955 ~]# systemctl status sshd.socket
?.sshd.socket - OpenSSH Server Socket
   Loaded: loaded (/usr/lib/systemd/system/sshd.socket; disabled; vendor preset: disabled)
   Active: inactive (dead) since Sat 2017-11-25 18:28:46 CST; 19s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
   Listen: [::]:22 (Stream)
 Accepted: 0; Connected: 0

Nov 25 18:28:12 CTU1000094955 systemd[1]: Listening on OpenSSH Server Socket.
Nov 25 18:28:12 CTU1000094955 systemd[1]: Starting OpenSSH Server Socket.
Nov 25 18:28:46 CTU1000094955 systemd[1]: Closed OpenSSH Server Socket.
Nov 25 18:28:46 CTU1000094955 systemd[1]: Stopping OpenSSH Server Socket.

24. 屏蔽（使它不能启动）或显示套接口

[root@CTU1000094955 ~]# systemctl mask sshd.socket
Created symlink from /etc/systemd/system/sshd.socket to /dev/null.
[root@CTU1000094955 ~]# systemctl unmask sshd.socket
Removed symlink /etc/systemd/system/sshd.socket.

服务的CPU利用率（分配额）

25. 获取当前某个服务的CPU分配额（如httpd）

[root@CTU1000094955 ~]# systemctl show -p CPUShares httpd.service
CPUShares=18446744073709551615

　　注意：各个服务的默认CPU分配份额=1024，你可以增加/减少某个进程的CPU分配份额。

26. 将某个服务（httpd.service）的CPU分配份额限制为2000 CPUShares/

[root@CTU1000094955 ~]# systemctl set-property httpd.service CPUShares=2000 
# systemctl show -p CPUShares httpd.service 
CPUShares=2000

　　注意：当你为某个服务设置CPUShares，会自动创建一个以服务名命名的目录（如 httpd.service），里面包含了一个名为90-CPUShares.conf的文件，该文件含有CPUShare限制信息，你可以通过以下方式查看该文件：

[root@CTU1000094955 ~]# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf 
[Service] 
CPUShares=2000

27. 检查某个服务的所有配置细节

[root@CTU1000094955 ~]# systemctl show httpd
Restart=no
NotifyAccess=none
RestartUSec=100ms
TimeoutStartUSec=1min 30s
TimeoutStopUSec=1min 30s
WatchdogUSec=0
WatchdogTimestampMonotonic=0
StartLimitInterval=10000000
StartLimitBurst=5
StartLimitAction=none
FailureAction=none
... ...  中间省略部分内容

28. 分析某个服务（httpd）的关键链

[root@CTU1000094955 ~]# systemd-analyze critical-chain firewalld.service
The time after the unit is active or started is printed after the "@" character.
The time the unit takes to start is printed after the "+" character.

firewalld.service +380ms
?..basic.target @5.903s
  ?..sockets.target @5.903s
    ?..rpcbind.socket @5.903s
      ?..sysinit.target @5.895s
        ?..systemd-update-utmp.service @5.877s +16ms
          ?..auditd.service @5.738s +135ms
            ?..systemd-tmpfiles-setup.service @5.661s +73ms
              ?..rhel-import-state.service @5.526s +134ms
                ?..local-fs.target @5.525s
                  ?..run-user-0.mount @14.041s
                    ?..local-fs-pre.target @1.615s
                      ?..systemd-tmpfiles-setup-dev.service @1.519s +92ms
                        ?..kmod-static-nodes.service @1.473s +44ms
                          ?..systemd-journald.socket
                            ?..-.slice

29. 获取某个服务（httpd）的依赖性列表

[root@CTU1000094955 ~]# systemctl list-dependencies firewalld.service
firewalld.service
?.?..system.slice
?.?..basic.target
?.  ?..alsa-restore.service
?.  ?..alsa-state.service
  ?.?.....
?.  ?..microcode.service
?.  ?..rhel-autorelabel-mark.service
?.  ?..rhel-autorelabel.service
?.  ?..rhel-configure.service
?.  ?..rhel-dmesg.service
?.  ?..rhel-loadmodules.service
?.  ?..paths.target
?.  ?..slices.target
... ....  后面省略部分内容

30. 按等级列出控制组

[root@CTU1000094955 ~]# systemd-cgls
?..1 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
?..user.slice
?.?..user-988.slice
?.?.?..session-c1.scope
?.?.  ?..3150 gdm-session-worker [pam/gdm-launch-environment]
?.?.  ?..3187 /usr/bin/gnome-session --autostart /usr/share/gdm/greeter/autostart --session gnome-initial-setup
?.?.  ?..3190 /usr/bin/dbus-launch --exit-with-session /usr/bin/gnome-session --autostart /usr/share/gdm/greeter/autostart --session gnome-initial-setup
?.?.  ?..3199 /bin/dbus-daemon --fork --print-pid 4 --print-address 6 --session
?.?.  ?..3288 /usr/libexec/at-spi-bus-launcher
?.?.  ?..3305 /bin/dbus-daemon --config-file=/etc/at-spi2/accessibility.conf --nofork --print-address 3
?.?.  ?..3309 /usr/libexec/at-spi2-registryd --use-gnome-session
?.?.  ?..3410 gnome-shell --mode=initial-setup
...  ...  中间省略部分内容
?.?.  ?..3767 /usr/libexec/ibus-engine-simple
?.?.  ?..3879 gnome-keyring-daemon --unlock
?.?..user-0.slice

31. 按CPU、内存、输入和输出列出控制组

[root@CTU1000094955 ~]# systemd-cgtop
Path                                                                                                                                                    Tasks   %CPU   Memory  Input/s Output/s

/                                                                                                                                                         418      -     2.8G        -        -
/system.slice/ModemManager.service                                                                                                                          1      -        -        -        -
/system.slice/NetworkManager.service                                                                                                                        1      -        -        -        -
/system.slice/abrt-oops.service                                                                                                                             1      -        -        -        -
/system.slice/abrt-xorg.service                                                                                                                             1      -        -        -        -
/system.slice/abrtd.service                                                                                                                                 1      -        -        -        -
/system.slice/accounts-daemon.service                                                                                                                       1      -        -        -        -
/system.slice/alsa-state.service                                                                                                                            1      -        -        -        -
/system.slice/atd.service                                                                                                                                   1      -        -        -        -
/system.slice/auditd.service                                                                                                                                3      -        -        -        -

控制系统运行等级

32. 启动系统救援模式

[root@CTU1000094955 ~]# systemctl rescue
Broadcast message from root@tecmint on pts/0(Wed2015-04-2911:31:18 IST):
The system is going down to rescue mode NOW!

33. 进入紧急模式

[root@CTU1000094955 ~]# systemctl emergency
Welcome to emergency mode!After logging in, type "journalctl -xb" to view
system logs,"systemctl reboot" to reboot,"systemctl default" to try again
to boot intodefault mode.

34. 列出当前使用的运行等级

　　运行等级说明如下。

Runlevel 0 : 关闭系统　　shutdown.target　　
Runlevel 1 : 紧急？维护模式　　emergency.target
Runlevel 2 : 救援？维护模式　　rescure.target
Runlevel 3 : 多用户，无图形系统　　multi-user.target
Runlevel 4 : 多用户，无图形系统　　无
Runlevel 5 : 多用户，图形化系统　　graphical.target
Runlevel 6 : 关闭并重启机器　　无

[root@CTU1000094955 ~]# systemctl get-default
graphical.target

35. 启动运行等级5，即图形模式

# systemctl isolate runlevel5.target
或
# systemctl isolate graphical.target
 

[root@CTU1000094955 ~]# systemctl isolate runlevel5.target
PolicyKit daemon disconnected from the bus.
We are no longer a registered authentication agent.

36. 启动运行等级3，即多用户模式（命令行）

# systemctl isolate runlevel3.target
或
# systemctl isolate multiuser.target

36. 设置多用户模式或图形模式为默认运行等级

# systemctl set-default runlevel3.target
# systemctl set-default runlevel5.target

37. 重启、停止、挂起、休眠系统或使系统进入混合睡眠

# systemctl reboot　　重新启动
# systemctl halt
# systemctl suspend　　进入睡眠模式
# systemctl hibernate　　进入休眠模式
# systemctl hybrid-sleep
# systemctl rescue　　强制进入救援模式
# systemctl emergency　　强制进入紧急救援模式
# systemctl poweroff　　系统关机

posted on 2017-11-25 17:29 kosamino 阅读(21436) 评论(1) 编辑收藏举报