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
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# systemd --version
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systemd 215
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+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
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# whereis systemd
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systemd:/usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz
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# whereis systemctl
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systemctl:/usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz
3. 检查systemd是否运行
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# ps -eaf | grep [s]ystemd
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root 10016:27?00:00:00/usr/lib/systemd/systemd --switched-root --system --deserialize 23
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root 4441016:27?00:00:00/usr/lib/systemd/systemd-journald
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root 4691016:27?00:00:00/usr/lib/systemd/systemd-udevd
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root 5551016:27?00:00:00/usr/lib/systemd/systemd-logind
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dbus 5561016:27?00:00:00/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
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# systemd-analyze
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Startup finished in487ms(kernel)+2.776s(initrd)+20.229s(userspace)=23.493s
5. 分析启动时各个进程花费的时间
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# systemd-analyze blame
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8.565s mariadb.service
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7.991s webmin.service
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6.095s postfix.service
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4.311s httpd.service
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3.926s firewalld.service
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3.780s kdump.service
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3.238s tuned.service
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1.712s network.service
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1.394s lvm2-monitor.service
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1.126s systemd-logind.service
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....
6. 分析启动时的关键链
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# systemd-analyze critical-chain
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The time after the unit is active or started is printed after the "@" character.
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The time the unit takes to start is printed after the "+" character.
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multi-user.target @20.222s
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└─mariadb.service @11.657s+8.565s
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└─network.target @11.168s
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└─network.service @9.456s+1.712s
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└─NetworkManager.service @8.858s+596ms
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└─firewalld.service @4.931s+3.926s
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└─basic.target @4.916s
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└─sockets.target @4.916s
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└─dbus.socket @4.916s
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└─sysinit.target @4.905s
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└─systemd-update-utmp.service @4.864s+39ms
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└─auditd.service @4.563s+301ms
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└─systemd-tmpfiles-setup.service @4.485s+69ms
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└─rhel-import-state.service @4.342s+142ms
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└─local-fs.target @4.324s
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└─boot.mount @4.286s+31ms
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└─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
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└─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device@4
重要:Systemctl接受服务(.service),挂载点(.mount),套接口(.socket)和设备(.device)作为单元。
7. 列出所有可用单元
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# systemctl list-unit-files
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UNIT FILE STATE
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proc-sys-fs-binfmt_misc.automount static
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dev-hugepages.mount static
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dev-mqueue.mount static
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proc-sys-fs-binfmt_misc.mount static
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sys-fs-fuse-connections.mount static
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sys-kernel-config.mount static
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sys-kernel-debug.mount static
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tmp.mount disabled
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brandbot.path disabled
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.....
8. 列出所有运行中单元
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# systemctl list-units
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UNIT LOAD ACTIVE SUB DESCRIPTION
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proc-sys-fs-binfmt_misc.automount loaded active waiting ArbitraryExecutableFileFormatsFileSyste
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sys-devices-pc...0-1:0:0:0-block-sr0.device loaded active plugged VBOX_CD-ROM
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sys-devices-pc...:00:03.0-net-enp0s3.device loaded active plugged PRO/1000 MT DesktopAdapter
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sys-devices-pc...00:05.0-sound-card0.device loaded active plugged 82801AA AC'97 Audio Controller
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sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged VBOX_HARDDISK
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sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
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sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged VBOX_HARDDISK
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sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS0
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sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1
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sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2
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sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3
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sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0
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sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-1
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sys-module-configfs.device loaded active plugged /sys/module/configfs
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...
9. 列出所有失败单元
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# systemctl --failed
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UNIT LOAD ACTIVE SUB DESCRIPTION
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kdump.service loaded failed failed Crash recovery kernel arming
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LOAD =Reflects whether the unit definition was properly loaded.
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ACTIVE =The high-level unit activation state, i.e. generalization of SUB.
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SUB =The low-level unit activation state, values depend on unit type.
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1 loaded units listed.Pass--all to see loaded but inactive units, too.
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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
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# systemctl is-enabled crond.service
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enabled
11. 检查某个单元或服务是否运行
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# systemctl status firewalld.service
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firewalld.service - firewalld -dynamic firewall daemon
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Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
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Active: active (running) since Tue2015-04-2816:27:55 IST;34min ago
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Main PID:549(firewalld)
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CGroup:/system.slice/firewalld.service
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└─549/usr/bin/python -Es/usr/sbin/firewalld --nofork --nopid
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Apr2816:27:51 tecmint systemd[1]:Starting firewalld -dynamic firewall daemon...
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Apr2816:27:55 tecmint 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)
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# systemctl list-unit-files --type=service
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UNIT FILE STATE
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arp-ethers.service disabled
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auditd.service enabled
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autovt@.service disabled
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blk-availability.service disabled
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brandbot.service static
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collectd.service disabled
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console-getty.service disabled
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console-shell.service disabled
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cpupower.service disabled
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crond.service enabled
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dbus-org.project.FirewallD1.service enabled
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....
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
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# systemctl start httpd.service
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# systemctl restart httpd.service
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# systemctl stop httpd.service
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# systemctl reload httpd.service
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# systemctl status httpd.service
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httpd.service -TheApache HTTP Server
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Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
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Active: active (running) since Tue2015-04-2817:21:30 IST;6s ago
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Process:2876ExecStop=/bin/kill -WINCH ${MAINPID}(code=exited, status=0/SUCCESS)
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Main PID:2881(httpd)
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Status:"Processing requests..."
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CGroup:/system.slice/httpd.service
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├─2881/usr/sbin/httpd -DFOREGROUND
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├─2884/usr/sbin/httpd -DFOREGROUND
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├─2885/usr/sbin/httpd -DFOREGROUND
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├─2886/usr/sbin/httpd -DFOREGROUND
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├─2887/usr/sbin/httpd -DFOREGROUND
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└─2888/usr/sbin/httpd -DFOREGROUND
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Apr2817:21:30 tecmint systemd[1]:StartingTheApache HTTP Server...
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Apr2817:21:30 tecmint httpd[2881]: AH00558: httpd:Couldnot reliably determine the server's fully q...ssage
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Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
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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)
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# systemctl is-active httpd.service
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# systemctl enable httpd.service
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# systemctl disable httpd.service
15. 如何屏蔽(让它不能启动)或显示服务(如 httpd.service)
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# systemctl mask httpd.service
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ln -s '/dev/null''/etc/systemd/system/httpd.service'
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# systemctl unmask httpd.service
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rm '/etc/systemd/system/httpd.service'
16. 使用systemctl命令杀死服务
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# systemctl kill httpd
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# systemctl status httpd
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httpd.service -TheApache HTTP Server
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Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
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Active: failed (Result:exit-code) since Tue2015-04-2818:01:42 IST;28min ago
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Main PID:2881(code=exited, status=0/SUCCESS)
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Status:"Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
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Apr2817:37:29 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:29 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:39 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:39 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:49 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:49 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:59 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2817:37:59 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
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Apr2818:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
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Apr2818:01:42 tecmint systemd[1]:Unit httpd.service entered failed state.
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Hint:Some lines were ellipsized,use-l to show in full.
使用Systemctl控制并管理挂载点
17. 列出所有系统挂载点
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# systemctl list-unit-files --type=mount
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UNIT FILE STATE
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dev-hugepages.mount static
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dev-mqueue.mount static
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proc-sys-fs-binfmt_misc.mount static
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sys-fs-fuse-connections.mount static
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sys-kernel-config.mount static
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sys-kernel-debug.mount static
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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
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# systemctl start tmp.mount
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# systemctl stop tmp.mount
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# systemctl restart tmp.mount
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# systemctl reload tmp.mount
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# systemctl status tmp.mount
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tmp.mount -TemporaryDirectory
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Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled)
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Active: active (mounted) since Tue2015-04-2817:46:06 IST;2min48s ago
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Where:/tmp
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What: tmpfs
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Docs: man:hier(7)
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http://
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Process:3908ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)
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Apr2817:46:06 tecmint systemd[1]:MountingTemporaryDirectory...
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Apr2817:46:06 tecmint systemd[1]: tmp.mount:Directory/tmp to mount over isnot empty, mounting anyway.
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Apr2817:46:06 tecmint systemd[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)
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# systemctl is-active tmp.mount
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# systemctl enable tmp.mount
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# systemctl disable tmp.mount
20. 在Linux中屏蔽(让它不能启用)或可见挂载点
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# systemctl mask tmp.mount
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ln -s '/dev/null''/etc/systemd/system/tmp.mount'
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# systemctl unmask tmp.mount
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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
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# systemctl list-unit-files --type=socket
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UNIT FILE STATE
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dbus.socket static
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dm-event.socket enabled
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lvm2-lvmetad.socket enabled
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rsyncd.socket disabled
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sshd.socket disabled
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syslog.socket static
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systemd-initctl.socket static
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systemd-journald.socket static
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systemd-shutdownd.socket static
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systemd-udevd-control.socket static
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systemd-udevd-kernel.socket static
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11 unit files listed.
22. 在Linux中启动、重启、停止、重载套接口并检查其状态
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# systemctl start cups.socket
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# systemctl restart cups.socket
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# systemctl stop cups.socket
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# systemctl reload cups.socket
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# systemctl status cups.socket
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cups.socket - CUPS PrintingServiceSockets
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Loaded: loaded (/usr/lib/systemd/system/cups.socket; enabled)
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Active: active (listening) since Tue2015-04-2818:10:59 IST;8s ago
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Listen:/var/run/cups/cups.sock (Stream)
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Apr2818:10:59 tecmint systemd[1]:Starting CUPS PrintingServiceSockets.
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Apr2818:10:59 tecmint systemd[1]:Listening on CUPS PrintingServiceSockets.
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)
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# systemctl is-active cups.socket
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# systemctl enable cups.socket
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# systemctl disable cups.socket
24. 屏蔽(使它不能启动)或显示套接口
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# systemctl mask cups.socket
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ln -s '/dev/null''/etc/systemd/system/cups.socket'
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# systemctl unmask cups.socket
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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)
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# systemctl show -p CPUShares httpd.service
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CPUShares=1024
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/
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# systemctl set-property httpd.service CPUShares=2000
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# systemctl show -p CPUShares httpd.service
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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:
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# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf
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[Service]
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CPUShares=2000
27. 检查某个服务的所有配置细节
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# systemctl show httpd
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Id=httpd.service
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Names=httpd.service
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Requires=basic.target
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Wants=system.slice
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WantedBy=multi-user.target
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Conflicts=shutdown.target
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Before=shutdown.target multi-user.target
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After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice
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Description=TheApache HTTP Server
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LoadState=loaded
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ActiveState=active
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SubState=running
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FragmentPath=/usr/lib/systemd/system/httpd.service
-
....
28. 分析某个服务(httpd)的关键链
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# systemd-analyze critical-chain httpd.service
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The time after the unit is active or started is printed after the "@" character.
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The time the unit takes to start is printed after the "+" character.
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httpd.service +142ms
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└─network.target @11.168s
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└─network.service @9.456s+1.712s
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└─NetworkManager.service @8.858s+596ms
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└─firewalld.service @4.931s+3.926s
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└─basic.target @4.916s
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└─sockets.target @4.916s
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└─dbus.socket @4.916s
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└─sysinit.target @4.905s
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└─systemd-update-utmp.service @4.864s+39ms
-
└─auditd.service @4.563s+301ms
-
└─systemd-tmpfiles-setup.service @4.485s+69ms
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└─rhel-import-state.service @4.342s+142ms
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└─local-fs.target @4.324s
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└─boot.mount @4.286s+31ms
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└─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service@4.092s+149ms
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└─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device@4.092s
29. 获取某个服务(httpd)的依赖性列表
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# systemctl list-dependencies httpd.service
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httpd.service
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├─system.slice
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└─basic.target
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├─firewalld.service
-
├─microcode.service
-
├─rhel-autorelabel-mark.service
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├─rhel-autorelabel.service
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├─rhel-configure.service
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├─rhel-dmesg.service
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├─rhel-loadmodules.service
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├─paths.target
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├─slices.target
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│├─-.slice
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│└─system.slice
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├─sockets.target
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│├─dbus.socket
-
....
30. 按等级列出控制组
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# systemd-cgls
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├─1/usr/lib/systemd/systemd --switched-root --system --deserialize 23
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├─user.slice
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│└─user-0.slice
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│└─session-1.scope
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│├─2498 sshd: root@pts/0
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│├─2500-bash
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│├─4521 systemd-cgls
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│└─4522 systemd-cgls
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└─system.slice
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├─httpd.service
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│├─4440/usr/sbin/httpd -DFOREGROUND
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│├─4442/usr/sbin/httpd -DFOREGROUND
-
│├─4443/usr/sbin/httpd -DFOREGROUND
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│├─4444/usr/sbin/httpd -DFOREGROUND
-
│├─4445/usr/sbin/httpd -DFOREGROUND
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│└─4446/usr/sbin/httpd -DFOREGROUND
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├─polkit.service
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│└─721/usr/lib/polkit-1/polkitd --no-debug
-
....
31. 按CPU、内存、输入和输出列出控制组
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# systemd-cgtop
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PathTasks%CPU MemoryInput/s Output/s
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/831.0437.8M--
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/system.slice -0.1---
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/system.slice/mariadb.service 20.1---
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/system.slice/tuned.service 10.0---
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/system.slice/httpd.service 60.0---
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/system.slice/NetworkManager.service 1----
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/system.slice/atop.service 1----
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/system.slice/atopacct.service 1----
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/system.slice/auditd.service 1----
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/system.slice/crond.service 1----
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/system.slice/dbus.service 1----
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/system.slice/firewalld.service 1----
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/system.slice/lvm2-lvmetad.service 1----
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/system.slice/polkit.service 1----
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/system.slice/postfix.service 3----
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/system.slice/rsyslog.service 1----
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/system.slice/system-getty.slice/getty@tty1.service 1----
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/system.slice/systemd-journald.service 1----
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/system.slice/systemd-logind.service 1----
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/system.slice/systemd-udevd.service 1----
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/system.slice/webmin.service 1----
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/user.slice/user-0.slice/session-1.scope3----
控制系统运行等级
32. 启动系统救援模式
-
# 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
-
# systemctl emergency
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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
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# 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
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# 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
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# systemctl reboot
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# systemctl halt
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# systemctl suspend
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# systemctl hibernate
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# systemctl hybrid-sleep
对于不知运行等级为何物的人,说明如下。
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Runlevel 0 : 关闭系统
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Runlevel 1 : 救援?维护模式
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Runlevel 3 : 多用户,无图形系统
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Runlevel 4 : 多用户,无图形系统
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Runlevel 5 : 多用户,图形化系统
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Runlevel 6 : 关闭并重启机器
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