RHCE7 -- systemctl命令

查询所有单元的状态:

[root@rhce7 ~]# systemctl
UNIT                                                  LOAD   ACTIVE SUB       DESCRIPTION
proc-sys-fs-binfmt_misc.automount                     loaded active waiting   Arbitrary Executable File Formats File System Automoun
sys-devices-pci00...get1::-:::-block-sr0.device loaded active plugged   VBOX_CD-ROM
sys-devices-pci0000:-::03.0-net-enp0s3.device loaded active plugged   PRO/ MT Desktop Adapter
sys-devices-pci00...-::05.0-sound-card0.device loaded active plugged   82801AA AC'97 Audio Controller
sys-devices-pci0000:-::08.0-net-enp0s8.device loaded active plugged   PRO/ MT Desktop Adapter
sys-devices-pci00...:-:::-block-sda-sda1.device loaded active plugged   VBOX_HARDDISK
sys-devices-pci00...:-:::-block-sda-sda2.device loaded active plugged   LVM PV ewUQqv-N1i5-9xcA-GRad-2BLV-qOTh-vNPOd2 on /dev/
sys-devices-pci00...get2::-:::-block-sda.device loaded active plugged   VBOX_HARDDISK
sys-devices-platform-serial8250-tty-ttyS0.device      loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS0
...

仅查询服务单元的状态:

[root@rhce7 ~]# systemctl --type=service
UNIT                                                   LOAD   ACTIVE SUB     DESCRIPTION
abrt-ccpp.service                                      loaded active exited  Install ABRT coredump hook
abrt-oops.service                                      loaded active running ABRT kernel log watcher
abrt-xorg.service                                      loaded active running ABRT Xorg log watcher
abrtd.service                                          loaded active running ABRT Automated Bug Reporting Tool
accounts-daemon.service                                loaded active running Accounts Service
...

查看处于失败或维护状态的任何单元:

[root@rhce7 ~]# systemctl status rngd.service -l
rngd.service - Hardware RNG Entropy Gatherer Daemon
   Loaded: loaded (/usr/lib/systemd/system/rngd.service; enabled)
   Active: failed (Result: exit-code) since Fri -- :: CST; 32min ago
  Process:  ExecStart=/sbin/rngd -f (code=exited, status=/FAILURE)
 Main PID:  (code=exited, status=/FAILURE)
   CGroup: /system.slice/rngd.service

Jul  :: rhce7.example.com systemd[]: Started Hardware RNG Entropy Gatherer Daemon.
Jul  :: rhce7.example.com rngd[]: Unable to open file: /dev/tpm0
Jul  :: rhce7.example.com rngd[]: can't open any entropy source
Jul  :: rhce7.example.com rngd[]: Maybe RNG device modules are not loaded
Jul  :: rhce7.example.com systemd[]: rngd.service: main process exited, code=exited, status=/FAILURE
Jul  :: rhce7.example.com systemd[]: Unit rngd.service entered failed state.
[root@rhce7 ~]# 

查看特定单元是否活动:

[root@rhce7 ~]# systemctl is-active sshd
active

查看特定单元是否已经开启自启动:

[root@rhce7 ~]# systemctl is-enabled sshd
enabled

列出所有已经加载单元的活动状态

[root@rhce7 ~]# systemctl list-units --type=service
UNIT                         LOAD   ACTIVE SUB     DESCRIPTION
abrt-ccpp.service            loaded active exited  Install ABRT coredump hook
abrt-oops.service            loaded active running ABRT kernel log watcher
abrt-xorg.service            loaded active running ABRT Xorg log watcher
abrtd.service                loaded active running ABRT Automated Bug Reporting
accounts-daemon.service      loaded active running Accounts Service
alsa-state.service           loaded active running Manage Sound Card State (rest
atd.service                  loaded active running Job spooling tools

查看所有单元的已启用和已禁用设置

[root@rhce7 ~]# 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 

查看失败的服务的状态

[root@rhce7 ~]# 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 

屏蔽服务
有时候可能安装了互相冲突的服务，比如network和NetworkManager，iptables和firewalld
可以将服务屏蔽。屏蔽将在配置目录中创建链接，使的启动该服务时不发生任何事

[root@rhce7 ~]# systemctl mask network
ln -s '/dev/null' '/etc/systemd/system/network.service'
[root@rhce7 ~]# systemctl unmask network
rm '/etc/systemd/system/network.service'

 禁用服务

[root@rhce7 ~]# systemctl disable network
network.service is not a native service, redirecting to /sbin/chkconfig.
Executing /sbin/chkconfig network off
[root@rhce7 ~]# 

禁用服务和屏蔽服务的区别：

·禁用服务：服务不会再系统系统的时候自动启动，也不会被其它单元文件启动，但可以手动启动

·屏蔽服务：无法手动启动，也无法自启动