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转自:一口Linux
在本教程中,我们将向您介绍在运行systemd的linux系统上如何使用systemctl命令工具有效的控制系统和服务.

Systemctl 介绍

Systemctl是一个systemd工具,主要负责控制systemd系统和服务管理器。
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,但并非总是如此。

开始Systemd和Systemctl 基础工具之旅

01、首先检查系统上是否安装了systemd以及当前安装的Systemd的版本是什么?
# systemd --version
systemd215
+PAM +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR
从上面的例子可以清楚地看出,我们已经安装了systemd 215版本。
02.检查systemd和systemctl的二进制文件和库的安装位置。
# whereis systemd
systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz
# whereis systemctl
systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz
03.检查systemd是否正在运行。
# ps -eaf | grep [s]ystemd
root10016:27?00:00:00/usr/lib/systemd/systemd--switched-root--system--deserialize23
root4441016:27?00:00:00/usr/lib/systemd/systemd-journald
root4691016:27?00:00:00/usr/lib/systemd/systemd-udevd
root5551016:27?00:00:00/usr/lib/systemd/systemd-logind
dbus5561016:27?00:00:00/bin/dbus-daemon--system--address=systemd:--nofork--nopidfile--systemd-activation
注意:systemd作为父守护进程运行(PID = 1)。 在上面的命令ps中使用(-e)选择所有进程,( - a)选择除会话前导之外的所有进程和(-f)选择完整格式列表(即-eaf)。
另请注意上面示例中的方括号以及其他示例。 Square Bracket表达式是grep的字符类模式匹配的一部分。
04.分析systemd启动过程
# systemd-analyze
Startupfinishedin487ms(kernel)+2.776s(initrd)+20.229s(userspace)=23.493s
05.分析每个进程在引导时花费的时间
#
systemd-analyzeblame
8
.565smariadb.service
7
.991swebmin.service
6
.095spostfix.service
4
.311shttpd.service
3
.926sfirewalld.service
3
.780skdump.service
3
.238stuned.service
1
.712snetwork.service
1
.394slvm2-monitor.service
1
.126ssystemd-logind.service
....
06.分析启动时的关键链
# 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.

multi-user.target @20.222s

└─mariadb.service @11.657s +8.565s

└─network.target @11.168s

└─network.service @9.456s +1.712s

└─NetworkManager.service @8.858s +596ms

└─firewalld.service @4.931s +3.926s

└─basic.target @4.916s

└─sockets.target @4.916s

└─dbus.socket @4.916s

└─sysinit.target @4.905s

└─systemd-update-utmp.service @4.864s +39ms

└─auditd.service @4.563s +301ms

└─systemd-tmpfiles-setup.service @4.485s +69ms

└─rhel-import-state.service @4.342s +142ms

└─local-fs.target @4.324s

└─boot.mount @4.286s +31ms

└─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096

└─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4
重要:Systemctl接受服务(.service),挂载点(.mount),套接字(.socket)和设备(.device)作为单位。
07、列出所有可用的单位
# systemctl list-unit-files
UNITFILESTATE
proc-sys-fs-binfmt_misc.automountstatic
dev-hugepages.mountstatic
dev-mqueue.mountstatic
proc-sys-fs-binfmt_misc.mountstatic
sys-fs-fuse-connections.mountstatic
sys-kernel-config.mountstatic
sys-kernel-debug.mountstatic
tmp.mountdisabled
brandbot.pathdisabled
.....
08、列出所有运行单元
# systemctl list-units
UNIT
LOAD
ACTIVE SUB DESCRIPTION

proc-
sys
-fs-binfmt_misc.automount loaded active waiting Arbitrary Executable
File
Formats
File
Syste

sys
-devices-pc..
.0-1
:
0
:
0
:
0
-
block
-sr0.device loaded active plugged VBOX_CD-ROM

sys
-devices-pc...:
00
:
03.0
-net-enp0s3.device loaded active plugged PRO/
1000
MT Desktop Adapter

sys
-devices-pc..
.00
:
05.0
-sound-card0.device loaded active plugged
82801
AA AC
'97 Audio Controller

sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged VBOX_HARDDISK

sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8

sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged VBOX_HARDDISK

sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS0

sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1

sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2

sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3

sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0

sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-1

sys-module-configfs.device loaded active plugged /sys/module/configfs

...
09、列出所有失败的单元
# systemctl --failed

UNIT
LOAD
ACTIVE SUB DESCRIPTION

kdump.service loaded
failedfailed
Crash
recovery
kernel arming

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.

1
loaded units listed. Pass
--all to see loaded but inactive units, too.
Toshowall
installed unit files
use'systemctl list-unit-files'
.
10、检查单元(cron.service)是否启用?
# systemctl is-enabled crond.service
enabled
11.检查单元或服务是否正在运行?
systemctlstatusfirewalld.service
firewalld.service-firewalld-dynamicfirewalldaemon
Loaded:loaded(/usr/lib/systemd/system/firewalld.service;enabled)
Active:active(running)sinceTue2018-04-2816:27:55IST;34minago
Main PID:549(firewalld)
CGroup:/system.slice/firewalld.service
└─549/usr/bin/python-Es/usr/sbin/firewalld--nofork--nopid
Apr2816:27:51tecmintsystemd[1]:Startingfirewalld-dynamicfirewalldaemon...
Apr2816:27:55tecmintsystemd[1]:Startedfirewalld-dynamicfirewalldaemon.
12.列出所有服务(包括启用和禁用)
# systemctl list-unit-files --
type
=service

UNIT FILE STATE

arp-ethers.service disabled

auditd.service enabled


blk-availability.service disabled

brandbot.service
static
collectd.service disabled

console
-getty.service disabled

console
-shell.service disabled

cpupower.service disabled

crond.service enabled

dbus-org.fedoraproject.FirewallD1.service enabled

....
13.如何在Linux中启动,重新启动,停止,重新加载和检查服务(httpd.service)的状态
# systemctl start httpd.service
# systemctl restart httpd.service
# systemctl stop httpd.service
# systemctl reload httpd.service
# systemctl status httpd.service
httpd.service-TheApacheHTTPServer
Loaded:loaded(/usr/lib/systemd/system/httpd.service;enabled)
Active:active(running)sinceTue2018-04-2817:21:30IST;6sago
Process:2876ExecStop=/bin/kill-WINCH${MAINPID}(code=exited,status=0/SUCCESS)
Main PID:2881(httpd)
Status:"Processing requests..."
CGroup:/system.slice/httpd.service
├─2881/usr/sbin/httpd-DFOREGROUND
├─2884/usr/sbin/httpd-DFOREGROUND
├─2885/usr/sbin/httpd-DFOREGROUND
├─2886/usr/sbin/httpd-DFOREGROUND
├─2887/usr/sbin/httpd-DFOREGROUND
└─2888/usr/sbin/httpd-DFOREGROUND
Apr2817:21:30tecmintsystemd[1]:StartingTheApacheHTTPServer...
Apr2817:21:30tecminthttpd[2881]:AH00558: httpd:Couldnotreliablydeterminetheserver'sfullyq...ssage
Apr2817:21:30tecmintsystemd[1]:StartedTheApacheHTTPServer.
Hint:Somelineswereellipsized,use-ltoshowinfull.
注意:当我们使用systemctl等启动,重启,停止和重载等命令时,我们将不会在终端上获得任何输出,只有status命令会打印输出。
14.如何在引导时激活服务并启用或禁用服务(系统引导时自动启动服务)
# systemctl is-active httpd.service
# systemctl enable httpd.service
# systemctl disable httpd.service
15.如何屏蔽(使其无法启动)或取消屏蔽服务(httpd.service)
ln
-s
'/dev/null''/etc/systemd/system/httpd.service'
# systemctl unmask httpd.service
rm
'/etc/systemd/system/httpd.service'
16.如何使用systemctl命令终止服务
# systemctl kill httpd
# systemctl status httpd
httpd.service-TheApacheHTTPServer
Loaded:loaded(/usr/lib/systemd/system/httpd.service;enabled)
Active:failed(Result:exit-code)sinceTue2018-04-2818:01:42IST;28minago
Main PID:2881(code=exited,status=0/SUCCESS)
Status:"Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
Apr2817:37:29tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:29tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:39tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:39tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:49tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:49tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:59tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2817:37:59tecmintsystemd[1]:httpd.service:GotnotificationmessagefromPID2881,butrecepti...bled.
Apr2818:01:42tecmintsystemd[1]:httpd.service:controlprocessexited,code=exitedstatus=226
Apr2818:01:42tecmintsystemd[1]:Unithttpd.serviceenteredfailedstate.
Hint:Somelineswereellipsized,use-ltoshowinfull.

使用Systemctl控制和管理挂载点

17.列出所有系统安装点
# systemctl list-unit-files --type=mount
UNIT FILE STATE

dev-hugepages.mount
static
dev-mqueue.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
18.如何装载,卸载,重新装载,重新装载系统装载点,以及检查系统上装载点的状态
# systemctl start tmp.mount
# systemctl stop tmp.mount
# systemctl restart tmp.mount
# systemctl reload tmp.mount
# systemctl status tmp.mount
tmp.mount-TemporaryDirectory
Loaded:loaded(/usr/lib/systemd/system/tmp.mount;disabled)
Active:active(mounted)sinceTue2018-04-2817:46:06IST;2min48sago
Where:/tmp
What:tmpfs
Docs:man:hier(7)
http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
Process:3908ExecMount=/bin/mounttmpfs/tmp-ttmpfs-omode=1777,strictatime(code=exited,status=0/SUCCESS)
Apr2817:46:06tecmintsystemd[1]:MountingTemporaryDirectory...
Apr2817:46:06tecmintsystemd[1]:tmp.mount:Directory/tmptomountoverisnotempty,mountinganyway.
Apr2817:46:06tecmintsystemd[1]:MountedTemporaryDirectory.
19.如何在引导时激活,启用或禁用装入点(在系统引导时自动装入)
# systemctl is-active tmp.mount
# systemctl enable tmp.mount
# systemctl disable tmp.mount
20.如何在Linux中屏蔽(使其无法启动)或取消屏蔽挂载点
# systemctl mask tmp.mount
ln
-s
'/dev/null''/etc/systemd/system/tmp.mount'
# systemctl unmask tmp.mount
rm
'/etc/systemd/system/tmp.mount'

使用Systemctl控制和管理套接字

21.列出所有可用的系统套接字。
# systemctl list-unit-files --type=socket
UNIT FILE STATE

dbus.socket
static
dm-
event
.socket enabled

lvm2-lvmetad.socket enabled

rsyncd.socket disabled

sshd.socket disabled

syslog.socket
static
systemd-initctl.socket
static
systemd-journald.socket
static
systemd-shutdownd.socket
static
systemd-udevd-control.socket
static
systemd-udevd-kernel.socket
static
11
unit files listed.
22.如何在Linux中启动,重新启动,停止,重新加载和检查套接字的状态(例如:cups.socket)
# systemctl start cups.socket
# systemctl restart cups.socket
# systemctl stop cups.socket
# systemctl reload cups.socket
# systemctl status cups.socket
cups.socket-CUPSPrintingServiceSockets
Loaded:loaded(/usr/lib/systemd/system/cups.socket;enabled)
Active:active(listening)sinceTue2015-04-2818:10:59IST;8sago
Listen:/var/run/cups/cups.sock(Stream)
Apr2818:10:59tecmintsystemd[1]:StartingCUPSPrintingServiceSockets.
Apr2818:10:59tecmintsystemd[1]:ListeningonCUPSPrintingServiceSockets.
23.如何激活套接字并在引导时启用或禁用(在系统引导时自动启动套接字)
# systemctl is-active cups.socket
# systemctl enable cups.socket
# systemctl disable cups.socket
24.如何屏蔽(使其无法启动)或取消屏蔽插座(cups.socket)
# systemctl mask cups.socket
ln
-s
'/dev/null''/etc/systemd/system/cups.socket'
# systemctl unmask cups.socket
rm
'/etc/systemd/system/cups.socket'

服务的CPU利用率(份额)

25.获取服务的当前CPU份额(比如httpd)
# systemctl show -p CPUShares httpd.service
CPUShares=1024
注意:每个服务的默认值都为CPUShare = 1024.您可以增加/减少进程的CPU份额。
26.将服务的CPU份额(httpd.service)限制为2000 CPUShares /
# systemctl set-property httpd.service CPUShares=2000
# systemctl show -p CPUShares httpd.service
CPUShares=2000
注意:为服务设置CPUShare时,会创建一个名为service的目录(httpd.service.d),其中包含一个包含CPUShare Limit信息的文件90-CPUShares.conf。 您可以将文件视为:
# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf
[Service]
CPUShares=2000
27.检查服务的所有配置详细信息
# systemctl show httpd
Id=httpd.service

Names=httpd.service

Requires=basic.target

Wants=system.slice

WantedBy=multi-user.target

Conflicts=shutdown.target

Before=shutdown.target multi-user.target

After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice

Description=The Apache HTTP Server

LoadState=loaded

ActiveState=active

SubState=running

FragmentPath=/usr/lib/systemd/system/httpd.service

....
28.分析服务的关键链(httpd)
# systemd-analyze critical-chain httpd.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.

httpd.service +142ms

└─network.target @11.168s

└─network.service @9.456s +1.712s

└─NetworkManager.service @8.858s +596ms

└─firewalld.service @4.931s +3.926s

└─basic.target @4.916s

└─sockets.target @4.916s

└─dbus.socket @4.916s

└─sysinit.target @4.905s

└─systemd-update-utmp.service @4.864s +39ms

└─auditd.service @4.563s +301ms

└─systemd-tmpfiles-setup.service @4.485s +69ms

└─rhel-import-state.service @4.342s +142ms

└─local-fs.target @4.324s

└─boot.mount @4.286s +31ms

└─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @4.092s +149ms

└─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4.092s
29.获取服务的依赖项列表(httpd)
#
systemctllist-dependencieshttpd.service
httpd.service
├─
system.slice
└─
basic.target
├─
firewalld.service
├─
microcode.service
├─
rhel-autorelabel-mark.service
├─
rhel-autorelabel.service
├─
rhel-configure.service
├─
rhel-dmesg.service
├─
rhel-loadmodules.service
├─
paths.target
├─
slices.target
│ ├─
-.slice
│ └─
system.slice
├─
sockets.target
│ ├─
dbus.socket
....
30.按层次列出控制组
# systemd-cgls
├─
1
/usr/lib/systemd/systemd --switched-root --
system
--deserialize
23
├─user.slice

│ └─user-
0
.slice

│ └─session-
1
.scope

│ ├─
2498
sshd: root@pts/
0
│ ├─
2500
-bash

│ ├─
4521
systemd-cgls

│ └─
4522
systemd-cgls

└─system.slice

├─httpd.service

│ ├─
4440
/usr/sbin/httpd -DFOREGROUND

│ ├─
4442
/usr/sbin/httpd -DFOREGROUND

│ ├─
4443
/usr/sbin/httpd -DFOREGROUND

│ ├─
4444
/usr/sbin/httpd -DFOREGROUND

│ ├─
4445
/usr/sbin/httpd -DFOREGROUND

│ └─
4446
/usr/sbin/httpd -DFOREGROUND

├─polkit.service

│ └─
721
/usr/lib/polkit-
1
/polkitd --
no
-debug

....
31.根据CPU,内存,输入和输出列出控制组
# systemd-cgtop
PathTasks%CPUMemoryInput/sOutput/s
/831.0437.8M--
/system.slice-0.1---
/system.slice/mariadb.service20.1---
/system.slice/tuned.service10.0---
/system.slice/httpd.service60.0---
/system.slice/NetworkManager.service1----
/system.slice/atop.service1----
/system.slice/atopacct.service1----
/system.slice/auditd.service1----
/system.slice/crond.service1----
/system.slice/dbus.service1----
/system.slice/firewalld.service1----
/system.slice/lvm2-lvmetad.service1----
/system.slice/polkit.service1----
/system.slice/postfix.service3----
/system.slice/rsyslog.service1----
/system.slice/system-getty.slice/[email protected]1----
/system.slice/systemd-journald.service1----
/system.slice/systemd-logind.service1----
/system.slice/systemd-udevd.service1----
/system.slice/webmin.service1----
/user.slice/user-0.slice/session-1.scope3----

控制系统运行级别

32.如何启动系统救援模式
# systemctl rescue
Broadcast message
from
root@tecmint
on
pts/
0
(Wed
2015-04-2911
:
31
:
18
IST):

The system
is
going down to rescue mode NOW!
33.如何进入紧急模式。
# 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级别
# systemctl
get
-
default
multi-user.target
5.如何启动Runlevel 5 aka图形模式。
# systemctl isolate runlevel5.target
OR
# systemctl isolate graphical.target
36.如何启动Runlevel 3又称多用户模式(命令行)
# systemctl isolate runlevel3.target
OR
# systemctl isolate multiuser.target
36.如何将多用户模式或图形模式设置为默认运行级别
# systemctl
set
-
default
runlevel3.target

# systemctl
set
-
default
runlevel5.target
37.如何重启,暂停,暂停,休眠或将系统置于混合睡眠状态
# systemctl reboot
# systemctl halt
# systemctl suspend
# systemctl hibernate
# systemctl hybrid-sleep
对于那些可能不了解跑步水平及其作用的人。
  • 运行级别0:关闭并关闭系统电源。
  • 运行级别1:救援?维护模式。
  • 运行级别3:多用户,无图形系统。
  • 运行级别4:多用户,无图形系统。
  • 运行级别5:多用户,图形系统。
  • 运行级别6:关闭并重新启动机器。
- EOF -
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