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。
使用Systemctl管理Linux服务
本文旨在阐明在运行systemd的系统上“如何控制系统和服务”。
Systemd初体验和Systemctl基础
1. 首先检查你的系统中是否安装有systemd并确定当前安装的版本
# systemd --version
systemd@H_403_31@215
+PAM+AUDIT+SELINUX+IMA+SYSVINIT+LIBCRYPTSETUP+GCRYPT+ACL+XZ-SECCOMP-APPARMOR
上例中很清楚地表明,我们安装了215版本的systemd。
2. 检查systemd和systemctl的二进制文件和库文件的安装位置
# whereis systemd
systemd:/usr/lib/systemd/etc/systemd/usr/share/systemd/usr/share/man/man1/systemd.@H_403_31@1.gz
# whereis systemctl
systemctl:/usr/bin/systemctl/usr/share/man/man1/systemctl.@H_403_31@1.gz
3. 检查systemd是否运行
# ps -eaf | grep [s]ystemd
root@H_403_31@1@H_403_31@0@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd--switched-root--system--deserialize@H_403_31@23
root@H_403_31@444@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-journald
root@H_403_31@469@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-udevd
root@H_403_31@555@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-logind
dbus@H_403_31@556@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/bin/dbus-daemon--system--address=systemd:--nofork--nopidfile--systemd-activation
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
# systemd-analyze
Startupfinishedin@H_403_31@487ms(kernel)+@H_403_31@2.776s(initrd)+@H_403_31@20.229s(userspace)=@H_403_31@23.493s
5. 分析启动时各个进程花费的时间
# systemd-analyze blame
@H_403_31@8.565smariadb.service
@H_403_31@7.991swebmin.service
@H_403_31@6.095spostfix.service
@H_403_31@4.311shttpd.service
@H_403_31@3.926sfirewalld.service
@H_403_31@3.780skdump.service
@H_403_31@3.238stuned.service
@H_403_31@1.712snetwork.service
@H_403_31@1.394slvm2-monitor.service
@H_403_31@1.126ssystemd-logind.service
....
6. 分析启动时的关键链
# systemd-analyze critical-chain
Thetime after the unitisactiveorstartedisprinted after the"@"character.
Thetime the unit takes to startisprinted after the"+"character.
multi-user.target@@H_403_31@20.222s
└─mariadb.service@@H_403_31@11.657s+@H_403_31@8.565s
└─network.target@@H_403_31@11.168s
└─network.service@@H_403_31@9.456s+@H_403_31@1.712s
└─NetworkManager.service@@H_403_31@8.858s+@H_403_31@596ms
└─firewalld.service@@H_403_31@4.931s+@H_403_31@3.926s
└─basic.target@@H_403_31@4.916s
└─sockets.target@@H_403_31@4.916s
└─dbus.socket@@H_403_31@4.916s
└─sysinit.target@@H_403_31@4.905s
└─systemd-update-utmp.service@@H_403_31@4.864s+@H_403_31@39ms
└─auditd.service@@H_403_31@4.563s+@H_403_31@301ms
└─systemd-tmpfiles-setup.service@@H_403_31@4.485s+@H_403_31@69ms
└─rhel-import-state.service@@H_403_31@4.342s+@H_403_31@142ms
└─local-fs.target@@H_403_31@4.324s
└─boot.mount@@H_403_31@4.286s+@H_403_31@31ms
└─systemd-fsck@dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d19608096
└─dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.device@@H_403_31@4
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
# systemctl list-unit-files
UNIT FILE STATE
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.mount disabled
brandbot.path disabled
.....
8. 列出所有运行中单元
# systemctl list-units
UNIT LOAD ACTIVE SUB DESCRIPTION
proc-sys-fs-binfmt_misc.automount loaded active waitingArbitraryExecutableFileFormatsFileSyste
sys-devices-pc...@H_403_31@0-@H_403_31@1:@H_403_31@0:@H_403_31@0:@H_403_31@0-block-sr0.device loaded active plugged VBox_CD-ROM
sys-devices-pc...:@H_403_31@00:@H_403_31@03.0-net-enp0s3.device loaded active plugged PRO/@H_403_31@1000MTDesktopAdapter
sys-devices-pc...@H_403_31@00:@H_403_31@05.0-sound-card0.device loaded active plugged@H_403_31@82801AAAC'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
...
9. 列出所有失败单元
# systemctl --Failed
UNIT LOAD ACTIVE SUB DESCRIPTION
kdump.service loaded Failed FailedCrashrecovery kernel arming
LOAD=Reflectswhether the unit definition was properly loaded.
ACTIVE=Thehigh-level unit activation state,i.e.generalization of SUB.
SUB=Thelow-level unit activation state,values depend on unit type.
@H_403_31@1loaded units listed.Pass--all to see loaded but inactive units,too.
Toshow all installed unit filesuse'systemctl list-unit-files'.
10. 检查某个单元(如 cron.service)是否启用
# systemctl is-enabled crond.service
enabled
11. 检查某个单元或服务是否运行
# systemctl status firewalld.service
firewalld.service-firewalld-dynamicfirewall daemon
Loaded:loaded(/usr/lib/systemd/system/firewalld.service;enabled)
Active:active(running)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@55IST;@H_403_31@34minago
MainPID:@H_403_31@549(firewalld)
CGroup:/system.slice/firewalld.service
└─@H_403_31@549/usr/bin/python-Es/usr/sbin/firewalld--nofork--nopid
Apr@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@51tecmint systemd[@H_403_31@1]:Startingfirewalld-dynamicfirewall daemon...
Apr@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@55tecmint systemd[@H_403_31@1]:Startedfirewalld-dynamicfirewall 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)
# systemctl list-unit-files --type=service
UNIT FILE STATE
arp-ethers.service disabled
auditd.service enabled
autovt@.service disabled
blk-availability.service disabled
brandbot.servicestatic
collectd.service disabled
console-getty.service disabled
console-shell.service disabled
cpupower.service disabled
crond.service enabled
dbus-org.Fedoraproject.FirewallD1.service enabled
....
13. Linux中如何启动、重启、停止、重载服务以及检查服务(如 httpd.service)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)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30IST;@H_403_31@6sago
Process:@H_403_31@2876ExecStop=/bin/kill-WINCH ${MAINPID}(code=exited,status=@H_403_31@0/SUCCESS)
MainPID:@H_403_31@2881(httpd)
Status:"Processing requests..."
CGroup:/system.slice/httpd.service
├─@H_403_31@2881/usr/sbin/httpd-DFOREGROUND
├─@H_403_31@2884/usr/sbin/httpd-DFOREGROUND
├─@H_403_31@2885/usr/sbin/httpd-DFOREGROUND
├─@H_403_31@2886/usr/sbin/httpd-DFOREGROUND
├─@H_403_31@2887/usr/sbin/httpd-DFOREGROUND
└─@H_403_31@2888/usr/sbin/httpd-DFOREGROUND
Apr@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30tecmint systemd[@H_403_31@1]:StartingTheApacheHTTPServer...
Apr@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30tecmint httpd[@H_403_31@2881]:AH00558:httpd:Couldnotreliably determine the server's fully q...ssage
Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized,use -l to show in full.
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)
# systemctl is-active httpd.service
# systemctl enable httpd.service
# systemctl disable httpd.service
15. 如何屏蔽(让它不能启动)或显示服务(如 httpd.service)
# systemctl mask httpd.service
ln-s'/dev/null''/etc/systemd/system/httpd.service'
# systemctl unmask httpd.service
rm'/etc/systemd/system/httpd.service'
16. 使用systemctl命令杀死服务
# systemctl kill httpd
# systemctl status httpd
httpd.service-TheApacheHTTPServer
Loaded:loaded(/usr/lib/systemd/system/httpd.service;enabled)
Active:Failed(Result:exit-code)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42IST;@H_403_31@28minago
MainPID:@H_403_31@2881(code=exited,status=@H_403_31@0/SUCCESS)
Status:"Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@29tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@29tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@39tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@39tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@49tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@49tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@59tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@59tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
Apr@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42tecmint systemd[@H_403_31@1]:httpd.service:control process exited,code=exited status=@H_403_31@226
Apr@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42tecmint systemd[@H_403_31@1]:Unithttpd.service entered Failed state.
Hint:Somelines were ellipsized,use-l to showinfull.
使用Systemctl控制并管理挂载点
17. 列出所有系统挂载点
# systemctl list-unit-files --type=mount
UNIT FILE STATE
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.mount disabled
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
# 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)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06IST;@H_403_31@2min@H_403_31@48sago
Where:/tmp
What:tmpfs
Docs:man:hier(@H_403_31@7)
http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
Process:@H_403_31@3908ExecMount=/bin/mount tmpfs/tmp-t tmpfs-o mode=@H_403_31@1777,strictatime(code=exited,status=@H_403_31@0/SUCCESS)
Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:MountingTemporaryDirectory...
Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:tmp.mount:Directory/tmp to mount overisnotempty,mounting anyway.
Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:MountedTemporaryDirectory.
19. 在启动时激活、启用或禁用挂载点(系统启动时自动挂载)
# systemctl is-active tmp.mount
# systemctl enable tmp.mount
# systemctl disable tmp.mount
20. 在Linux中屏蔽(让它不能启用)或可见挂载点
# 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控制并管理套接口
21. 列出所有可用系统套接口
# systemctl list-unit-files --type=socket
UNIT FILE STATE
dbus.socketstatic
dm-event.socket enabled
lvm2-lvMetad.socket enabled
rsyncd.socket disabled
sshd.socket disabled
syslog.socketstatic
systemd-initctl.socketstatic
systemd-journald.socketstatic
systemd-shutdownd.socketstatic
systemd-udevd-control.socketstatic
systemd-udevd-kernel.socketstatic
@H_403_31@11unit files listed.
22. 在Linux中启动、重启、停止、重载套接口并检查其状态
# 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)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59IST;@H_403_31@8sago
Listen:/var/run/cups/cups.sock(Stream)
Apr@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59tecmint systemd[@H_403_31@1]:StartingCUPSPrintingServiceSockets.
Apr@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59tecmint systemd[@H_403_31@1]:Listeningon CUPSPrintingServiceSockets.
23. 在启动时激活套接口,并启用或禁用它(系统启动时自启动)
# systemctl is-active cups.socket
# systemctl enable cups.socket
# systemctl disable cups.socket
24. 屏蔽(使它不能启动)或显示套接口
# 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(分配额)
25. 获取当前某个服务的cpu分配额(如httpd)
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/
# systemctl set-property httpd.service cpuShares=2000
# systemctl show -p cpuShares httpd.service
cpuShares=@H_403_31@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:
27. 检查某个服务的所有配置细节
# 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=TheApacheHTTPServer
LoadState=loaded
ActiveState=active
SubState=running
FragmentPath=/usr/lib/systemd/system/httpd.service
....
28. 分析某个服务(httpd)的关键链
# systemd-analyze critical-chain httpd.service
Thetime after the unitisactiveorstartedisprinted after the"@"character.
Thetime the unit takes to startisprinted after the"+"character.
httpd.service+@H_403_31@142ms
└─network.target@@H_403_31@11.168s
└─network.service@@H_403_31@9.456s+@H_403_31@1.712s
└─NetworkManager.service@@H_403_31@8.858s+@H_403_31@596ms
└─firewalld.service@@H_403_31@4.931s+@H_403_31@3.926s
└─basic.target@@H_403_31@4.916s
└─sockets.target@@H_403_31@4.916s
└─dbus.socket@@H_403_31@4.916s
└─sysinit.target@@H_403_31@4.905s
└─systemd-update-utmp.service@@H_403_31@4.864s+@H_403_31@39ms
└─auditd.service@@H_403_31@4.563s+@H_403_31@301ms
└─systemd-tmpfiles-setup.service@@H_403_31@4.485s+@H_403_31@69ms
└─rhel-import-state.service@@H_403_31@4.342s+@H_403_31@142ms
└─local-fs.target@@H_403_31@4.324s
└─boot.mount@@H_403_31@4.286s+@H_403_31@31ms
└─systemd-fsck@dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.service@@H_403_31@4.092s+@H_403_31@149ms
└─dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.device@@H_403_31@4.092s
29. 获取某个服务(httpd)的依赖性列表
# systemctl list-dependencies httpd.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. 按等级列出控制组
# systemd-cgls
├─@H_403_31@1/usr/lib/systemd/systemd--switched-root--system--deserialize@H_403_31@23
├─user.slice
│└─user-@H_403_31@0.slice
│└─session-@H_403_31@1.scope
│├─@H_403_31@2498sshd:root@pts/@H_403_31@0
│├─@H_403_31@2500-bash
│├─@H_403_31@4521systemd-cgls
│└─@H_403_31@4522systemd-cgls
└─system.slice
├─httpd.service
│├─@H_403_31@4440/usr/sbin/httpd-DFOREGROUND
│├─@H_403_31@4442/usr/sbin/httpd-DFOREGROUND
│├─@H_403_31@4443/usr/sbin/httpd-DFOREGROUND
│├─@H_403_31@4444/usr/sbin/httpd-DFOREGROUND
│├─@H_403_31@4445/usr/sbin/httpd-DFOREGROUND
│└─@H_403_31@4446/usr/sbin/httpd-DFOREGROUND
├─polkit.service
│└─@H_403_31@721/usr/lib/polkit-@H_403_31@1/polkitd--no-debug
....
31. 按cpu、内存、输入和输出列出控制组
# systemd-cgtop
PathTasks%cpuMemoryInput/sOutput/s
/@H_403_31@83@H_403_31@1.0@H_403_31@437.8M--
/system.slice-@H_403_31@0.1---
/system.slice/mariadb.service@H_403_31@2@H_403_31@0.1---
/system.slice/tuned.service@H_403_31@1@H_403_31@0.0---
/system.slice/httpd.service@H_403_31@6@H_403_31@0.0---
/system.slice/NetworkManager.service@H_403_31@1----
/system.slice/atop.service@H_403_31@1----
/system.slice/atopacct.service@H_403_31@1----
/system.slice/auditd.service@H_403_31@1----
/system.slice/crond.service@H_403_31@1----
/system.slice/dbus.service@H_403_31@1----
/system.slice/firewalld.service@H_403_31@1----
/system.slice/lvm2-lvMetad.service@H_403_31@1----
/system.slice/polkit.service@H_403_31@1----
/system.slice/postfix.service@H_403_31@3----
/system.slice/rsyslog.service@H_403_31@1----
/system.slice/system-getty.slice/getty@tty1.service@H_403_31@1----
/system.slice/systemd-journald.service@H_403_31@1----
/system.slice/systemd-logind.service@H_403_31@1----
/system.slice/systemd-udevd.service@H_403_31@1----
/system.slice/webmin.service@H_403_31@1----
/user.slice/user-@H_403_31@0.slice/session-@H_403_31@1.scope@H_403_31@3----
@H_502_6370@ 控制系统运行等级
32. 启动系统救援模式
# systemctl rescue
Broadcastmessagefromroot@tecmint on pts/@H_403_31@0(Wed@H_403_31@2015-@H_403_31@04-@H_403_31@29@H_403_31@11:@H_403_31@31:@H_403_31@18IST):
Thesystemisgoing down torescuemode NOW!
33. 进入紧急模式
# systemctl emergency
Welcometo emergency mode!Afterloggingin,type"journalctl -xb"to view
system logs,"systemctl reboot"to reboot,"systemctl default"totryagain
to bootintodefaultmode.
34. 列出当前使用的运行等级
# systemctl get-default
multi-user.target
35. 启动运行等级5,即图形模式
# systemctl isolate runlevel5.target
或
# systemctl isolate graphical.target
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
# systemctl halt
# systemctl suspend
# systemctl hibernate
# systemctl hybrid-sleep
对于不知运行等级为何物的人,说明如下。
- Runlevel 0 : 关闭系统
- Runlevel 1 : 救援?维护模式
- Runlevel 3 : 多用户,无图形系统
- Runlevel 4 : 多用户,无图形系统
- Runlevel 5 : 多用户,图形化系统
- Runlevel 6 : 关闭并重启机器