📅  最后修改于: 2020-10-31 13:27:27             🧑  作者: Mango
systemctl是用于控制systemd的实用程序。 systemctl为CentOS管理员提供了在systemd上执行多种操作的能力,包括-
systemctl的命令语法非常基本,但是可以与开关和选项纠缠在一起。我们将介绍管理CentOS Linux所需的systemctl最基本的功能。
Basic systemctl syntax:
systemctl [OPTIONS] COMMAND [NAME]
以下是与systemctl一起使用的常见命令-
我们已经使用systemctl讨论了start , stop , reload , restart , enable和disable 。因此,让我们来看一下其余的常用命令。
以最简单的形式,status命令可用于查看整个系统的状态-
[root@localhost rdc]# systemctl status
● localhost.localdomain
State: running
Jobs: 0 queued
Failed: 0 units
Since: Thu 2017-01-19 19:14:37 EST; 4h 5min ago
CGroup: /
├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
├─user.slice
│ └─user-1002.slice
│ └─session-1.scope
│ ├─2869 gdm-session-worker [pam/gdm-password]
│ ├─2881 /usr/bin/gnome-keyring-daemon --daemonize --login
│ ├─2888 gnome-session --session gnome-classic
│ ├─2895 dbus-launch --sh-syntax --exit-with-session
以上输出已压缩。在实际系统中, ctl status将输出约100行树状进程状态。
假设我们要检查防火墙服务的状态-
[root@localhost rdc]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2017-01-19 19:14:55 EST; 4h 12min ago
Docs: man:firewalld(1)
Main PID: 825 (firewalld)
CGroup: /system.slice/firewalld.service
└─825 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
如您所见,我们的防火墙服务当前处于活动状态,并且已经运行了4多个小时。
list-units命令允许我们列出某种类型的所有单位。让我们检查一下systemd管理的套接字-
[root@localhost]# systemctl list-units --type=socket
UNIT LOAD ACTIVE SUB DESCRIPTION
avahi-daemon.socket loaded active running Avahi mDNS/DNS-SD Stack Activation Socket
cups.socket loaded active running CUPS Printing Service Sockets
dbus.socket loaded active running D-Bus System Message Bus Socket
dm-event.socket loaded active listening Device-mapper event daemon FIFOs
iscsid.socket loaded active listening Open-iSCSI iscsid Socket
iscsiuio.socket loaded active listening Open-iSCSI iscsiuio Socket
lvm2-lvmetad.socket loaded active running LVM2 metadata daemon socket
lvm2-lvmpolld.socket loaded active listening LVM2 poll daemon socket
rpcbind.socket loaded active listening RPCbind Server Activation Socket
systemd-initctl.socket loaded active listening /dev/initctl Compatibility Named Pipe
systemd-journald.socket loaded active running Journal Socket
systemd-shutdownd.socket loaded active listening Delayed Shutdown Socket
systemd-udevd-control.socket loaded active running udev Control Socket
systemd-udevd-kernel.socket loaded active running udev Kernel Socket
virtlockd.socket loaded active listening Virtual machine lock manager socket
virtlogd.socket loaded active listening Virtual machine log manager socket
现在让我们检查当前正在运行的服务-
[root@localhost rdc]# 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 Tool
accounts-daemon.service loaded active running Accounts Service
alsa-state.service loaded active running Manage Sound Card State (restore and store)
atd.service loaded active running Job spooling tools
auditd.service loaded active running Security Auditing Service
is-active命令是设计用来返回单元状态信息的systemctl命令的示例。
[root@localhost rdc]# systemctl is-active ksm.service
active
cat是很少使用的命令之一。不用在外壳上使用cat并输入单位文件的路径,只需使用systemctl cat即可。
[root@localhost]# systemctl cat firewalld
# /usr/lib/systemd/system/firewalld.service
[Unit]
Description=firewalld - dynamic firewall daemon
Before=network.target
Before=libvirtd.service
Before = NetworkManager.service
After=dbus.service
After=polkit.service
Conflicts=iptables.service ip6tables.service ebtables.service ipset.service
Documentation=man:firewalld(1)
[Service]
EnvironmentFile = -/etc/sysconfig/firewalld
ExecStart = /usr/sbin/firewalld --nofork --nopid $FIREWALLD_ARGS
ExecReload = /bin/kill -HUP $MAINPID
# supress to log debug and error output also to /var/log/messages
StandardOutput = null
StandardError = null
Type = dbus
BusName = org.fedoraproject.FirewallD1
[Install]
WantedBy = basic.target
Alias = dbus-org.fedoraproject.FirewallD1.service
[root@localhost]#
现在,我们已经更详细地研究了systemd和systemctl ,让我们使用它们来管理cgroups或control group中的资源。