10.23 linux任务计划cron
我们可能有这样的需求：在凌晨的时候做一些操作，例如备份数据、重启服务等。这样就需要借助任务计划去实现。
linux的任务计划服务：cron。cron的配置文件定义了执行的SHELL，执行命令的PATH等，还定义了时间的格式。
[root@lgs ~]# cat /etc/crontab SHELL=/bin/bashPATH=/sbin:/bin:/usr/sbin:/usr/binMAILTO=root# For details see man 4 crontabs# Example of job definition:# .---------------- minute (0 - 59)# | .------------- hour (0 - 23)# | | .---------- day of month (1 - 31)# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat# | | | | |# * * * * * user-name command to be executed
编辑任务计划：crontab -e，像vim一样的操作进行编辑。
[root@lgs ~]# crontab -eno crontab for root - using an empty one0 3 * * * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.logcrontab: installing new crontab[root@lgs ~]# cat /var/spool/cron/root0 3 * * * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log
每月的1-10号执行：
0 3 1-10 * * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log
双月份执行：
0 3 * */2 * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log
双月份的周2、周5执行，用逗号分割：
0 3 * */2 2,5 /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log
确保cron会执行，要启动crond服务：
[root@lgs ~]# systemctl start crond[root@lgs ~]# systemctl status crond● crond.service - Command Scheduler Loaded: loaded (/usr/lib/systemd/system/crond.service; enabled; vendor preset: enabled) Active: active (running) since 日 2018-05-13 11:47:51 CST; 10min ago Main PID: 572 (crond) CGroup: /system.slice/crond.service └─572 /usr/sbin/crond -n5月 13 11:47:51 lgs systemd[1]: Started Command Scheduler.5月 13 11:47:51 lgs systemd[1]: Starting Command Scheduler...5月 13 11:47:51 lgs crond[572]: (CRON) INFO (RANDOM_DELAY will be scaled with factor 74% if used.)5月 13 11:47:51 lgs crond[572]: (CRON) INFO (running with inotify support)
为什么有些时候，写了计划，就是没有按计划执行：
可能是脚本里的命令，没有用到绝对路径。这是因为crontab的配置文件里定义的PATH，没有你执行的命令的路径。解决办法就是执行的脚本命令要写绝对路径，要么把命令的绝对路径加入到crontab的配置文件里的PATH中去。
一般尽量别修改配置文件，而是命令用绝对路径编写比较好。
任务计划要追加执行日志，方便以后可查，养成好的习惯。
列出系统的任务计划：
[root@lgs ~]# crontab -l0 3 * * * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log
备份任务计划：备份文件即可，一般以用户的名字命名的cron文件。
[root@lgs ~]# ls -l /var/spool/cron/总用量 4-rw------- 1 root root 63 5月 13 11:54 root
-u选项：指定用户。不指定默认是root。
[root@lgs ~]# crontab -u root -l0 3 * * * /bin/bash /usr/123.sh >>/tmp/123.log 2>>/tmp/123.log[root@lgs ~]# crontab -u lgs -lno crontab for lgs
-r选项：删除计划
[root@lgs ~]# crontab -r [root@lgs ~]# crontab -u root -lno crontab for root
10.24 chkconfig工具
系统里像crond、iptables、nginx、httpd、mysql都是服务的形式运行。系统怎么去控制管理这些服务的启动、开机启动、指定级别开机启动等。就要用到chkconfig。
linux的系统服务管理：CentOS 5、6的时候使用chkconfig。
CentOS7也可以用chkconfig，但是比较少用，主要用systemd来管理服务。
列出服务：用chkconfig只列出用chkconfig管理的服务，即sysV机制的，不含systemd管理的[root@lgs ~]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:开 3:开 4:开 5:开 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
CentOS 5、6：进程id为1 的是init（sysV机制），在/etc/init.d/ 下
CentOS7：进程id为1 的是 systemd。
某服务关闭开机启动：（针对2345级别，因为016级别开机启动没意义）
[root@lgs ~]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:开 3:开 4:开 5:开 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关[root@lgs ~]# chkconfig mysqld off[root@lgs ~]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:关 3:关 4:关 5:关 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
某服务开机启动：（针对2345级别，因为016级别开机启动没意义）
[root@lgs ~]# chkconfig mysqld on[root@lgs ~]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:开 3:开 4:开 5:开 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
指定级别开机启动或关闭：
[root@lgs ~]# chkconfig --level 45 mysqld off[root@lgs ~]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:开 3:开 4:关 5:关 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
要把用户自定义（自己安装的）服务加入chkconfig列表去管理：chkconfig --add
（服务的文件必须在/etc/init.d/ 下）
[root@lgs ~]# chkconfig --add 123服务 123 信息读取出错：没有那个文件或目录[root@lgs ~]# cd /etc/init.d/[root@lgs init.d]# lsfunctions httpd mysqld netconsole network README[root@lgs init.d]# cp network 123[root@lgs init.d]# chkconfig --add 123[root@lgs init.d]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。123 0:关 1:关 2:开 3:开 4:开 5:开 6:关mysqld 0:关 1:关 2:开 3:开 4:关 5:关 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
123脚本或者服务要被chkconfig识别，必须在脚本里编写以下参数
chkconfig: 2345 10 90：2345运行级别启动、10位启动、90位关闭。
[root@lgs init.d]# cat 123# chkconfig: 2345 10 90# description: Activates/Deactivates all network interfaces configured to \# start at boot time.
删除列表中的服务：
[root@lgs init.d]# chkconfig --del 123[root@lgs init.d]# chkconfig --list注：该输出结果只显示 SysV 服务，并不包含原生 systemd 服务。SysV 配置数据可能被原生 systemd 配置覆盖。 要列出 systemd 服务，请执行 'systemctl list-unit-files'。 查看在具体 target 启用的服务请执行 'systemctl list-dependencies [target]'。mysqld 0:关 1:关 2:开 3:开 4:关 5:关 6:关netconsole 0:关 1:关 2:关 3:关 4:关 5:关 6:关network 0:关 1:关 2:开 3:开 4:开 5:开 6:关
10.25 systemd管理服务
在CentOS7中， 主要用systemd管理服务，chkconfig已经很少使用。
查看所有服务：service、target、socket等类型。
[root@lgs ~]# systemctl list-unit-filesUNIT FILE STATE proc-sys-fs-binfmt_misc.automount static 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 disabledbrandbot.path disabledsystemd-ask-password-console.path static systemd-ask-password-plymouth.path static systemd-ask-password-wall.path static session-2.scope static session-4.scope static accounts-daemon.service enabled arp-ethers.service disabledauditd.service enabled autovt@.service enabled blk-availability.service disabledbluetooth.service enabled brandbot.service static canberra-system-bootup.service disabledcanberra-system-shutdown-reboot.service disabledcanberra-system-shutdown.service disabledchrony-dnssrv@.service static chrony-wait.service disabledchronyd.service enabled colord.service static console-getty.service disabledconsole-shell.service disabledcontainer-getty@.service static cpupower.service disabledcrond.service enabled dbus-org.bluez.service enabled dbus-org.freedesktop.hostname1.service static dbus-org.freedesktop.import1.service static dbus-org.freedesktop.locale1.service static dbus-org.freedesktop.login1.service static dbus-org.freedesktop.machine1.service static dbus-org.freedesktop.NetworkManager.service enabled dbus-org.freedesktop.nm-dispatcher.service enabled dbus-org.freedesktop.timedate1.service static dbus.service static debug-shell.service disableddisplay-manager.service enabled dm-event.service disableddracut-cmdline.service static dracut-initqueue.service static dracut-mount.service static dracut-pre-mount.service static dracut-pre-pivot.service static dracut-pre-trigger.service static dracut-pre-udev.service static dracut-shutdown.service static ebtables.service disabledemergency.service static firewalld.service disabledfstrim.service static gdm.service enabled geoclue.service static getty@.service enabled halt-local.service static initrd-cleanup.service static initrd-parse-etc.service static initrd-switch-root.service static initrd-udevadm-cleanup-db.service static ip6tables.service disablediprdump.service disablediprinit.service disablediprupdate.service disablediptables.service enabled irqbalance.service enabled kdump.service enabled kmod-static-nodes.service static lvm2-lvmetad.service disabledlvm2-lvmpolld.service disabledlvm2-monitor.service enabled lvm2-pvscan@.service static messagebus.service static microcode.service enabled NetworkManager-dispatcher.service enabled NetworkManager-wait-online.service disabledNetworkManager.service enabled oddjobd.service disabledplymouth-halt.service disabledplymouth-kexec.service disabledplymouth-poweroff.service disabledplymouth-quit-wait.service disabledplymouth-quit.service disabledplymouth-read-write.service disabledplymouth-reboot.service disabledplymouth-start.service disabledplymouth-switch-root.service static polkit.service static postfix.service enabled quotaon.service static rc-local.service static rdisc.service disabledrealmd.service static rescue.service static rhel-autorelabel-mark.service static rhel-autorelabel.service static rhel-configure.service static rhel-dmesg.service disabledrhel-domainname.service disabledrhel-import-state.service static rhel-loadmodules.service static rhel-readonly.service static rsyslog.service enabled rtkit-daemon.service enabled selinux-policy-migrate-local-changes@.service static serial-getty@.service disabledsshd-keygen.service static sshd.service enabled sshd@.service static sysstat.service enabled systemd-ask-password-console.service static systemd-ask-password-plymouth.service static systemd-ask-password-wall.service static systemd-backlight@.service static systemd-binfmt.service static systemd-bootchart.service disabledsystemd-firstboot.service static systemd-fsck-root.service static systemd-fsck@.service static systemd-halt.service static systemd-hibernate-resume@.service static systemd-hibernate.service static systemd-hostnamed.service static systemd-hwdb-update.service static systemd-hybrid-sleep.service static systemd-importd.service static systemd-initctl.service static systemd-journal-catalog-update.service static systemd-journal-flush.service static systemd-journald.service static systemd-kexec.service static systemd-localed.service static systemd-logind.service static systemd-machine-id-commit.service static systemd-machined.service static systemd-modules-load.service static systemd-nspawn@.service disabledsystemd-poweroff.service static systemd-quotacheck.service static systemd-random-seed.service static systemd-readahead-collect.service enabled systemd-readahead-done.service indirectsystemd-readahead-drop.service enabled systemd-readahead-replay.service enabled systemd-reboot.service static systemd-remount-fs.service static systemd-rfkill@.service static systemd-shutdownd.service static systemd-suspend.service static systemd-sysctl.service static systemd-timedated.service static systemd-tmpfiles-clean.service static systemd-tmpfiles-setup-dev.service static systemd-tmpfiles-setup.service static systemd-udev-settle.service static systemd-udev-trigger.service static systemd-udevd.service static systemd-update-done.service static systemd-update-utmp-runlevel.service static systemd-update-utmp.service static systemd-user-sessions.service static systemd-vconsole-setup.service static tcsd.service disabledteamd@.service static tuned.service enabled upower.service disabledvgauthd.service enabled vmtoolsd.service enabled wpa_supplicant.service disabled-.slice static machine.slice static system.slice static user-0.slice static user.slice static dbus.socket static dm-event.socket enabled lvm2-lvmetad.socket enabled lvm2-lvmpolld.socket enabled sshd.socket disabledsyslog.socket static systemd-initctl.socket static systemd-journald.socket static systemd-shutdownd.socket static systemd-udevd-control.socket static systemd-udevd-kernel.socket static basic.target static bluetooth.target static cryptsetup-pre.target static cryptsetup.target static ctrl-alt-del.target disableddefault.target enabled emergency.target static final.target static getty.target static graphical.target static halt.target disabledhibernate.target static hybrid-sleep.target static initrd-fs.target static initrd-root-fs.target static initrd-switch-root.target static initrd.target static iprutils.target disabledkexec.target disabledlocal-fs-pre.target static local-fs.target static machines.target disabledmulti-user.target enabled network-online.target static network-pre.target static network.target static nss-lookup.target static nss-user-lookup.target static paths.target static poweroff.target disabledprinter.target static reboot.target disabledremote-fs-pre.target static remote-fs.target enabled rescue.target disabledrpcbind.target static runlevel0.target disabledrunlevel1.target disabledrunlevel2.target enabled runlevel3.target enabled runlevel4.target enabled runlevel5.target static runlevel6.target disabledshutdown.target static sigpwr.target static sleep.target static slices.target static smartcard.target static sockets.target static sound.target static suspend.target static swap.target static sysinit.target static system-update.target static time-sync.target static timers.target static umount.target static chrony-dnssrv@.timer disabledfstrim.timer disabledsystemd-readahead-done.timer indirectsystemd-tmpfiles-clean.timer static 252 unit files listed.lines 210-255/255 (END)
指定类型list：
[root@lgs ~]# systemctl list-units --type=service UNIT LOAD ACTIVE SUB DESCRIPTION auditd.service loaded active running Security Auditing Service chronyd.service loaded active running NTP client/server crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus getty@tty1.service loaded active running Getty on tty1 iptables.service loaded active exited IPv4 firewall with iptables irqbalance.service loaded active running irqbalance daemon kdump.service loaded active exited Crash recovery kernel arming kmod-static-nodes.service loaded active exited Create list of required static device nodes for the current kernel lvm2-lvmetad.service loaded active running LVM2 metadata daemon lvm2-monitor.service loaded active exited Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling lvm2-pvscan@8:17.service loaded active exited LVM2 PV scan on device 8:17 lvm2-pvscan@8:18.service loaded active exited LVM2 PV scan on device 8:18 lvm2-pvscan@8:19.service loaded active exited LVM2 PV scan on device 8:19 mysqld.service loaded active running LSB: start and stop MySQL network.service loaded active exited LSB: Bring up/down networking NetworkManager-wait-online.service loaded active exited Network Manager Wait Online NetworkManager.service loaded active running Network Manager polkit.service loaded active running Authorization Manager postfix.service loaded active running Postfix Mail Transport Agent● rc-local.service loaded failed failed /etc/rc.d/rc.local Compatibility rhel-autorelabel-mark.service loaded active exited Mark the need to relabel after reboot rhel-dmesg.service loaded active exited Dump dmesg to /var/log/dmesg
--all选项：显示所有的service（包括active激活的和inactive未激活的）
[root@lgs ~]# systemctl list-units --all --type=service UNIT LOAD ACTIVE SUB DESCRIPTION accounts-daemon.service loaded inactive dead Accounts Service auditd.service loaded active running Security Auditing Service brandbot.service loaded inactive dead Flexible Branding Service chronyd.service loaded active running NTP client/server cpupower.service loaded inactive dead Configure CPU power related settings crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus dm-event.service loaded inactive dead Device-mapper event daemon dracut-shutdown.service loaded inactive dead Restore /run/initramfs emergency.service loaded inactive dead Emergency Shell● exim.service not-found inactive dead exim.service gdm.service loaded inactive dead GNOME Display Manager getty@tty1.service loaded active running Getty on tty1 ip6tables.service loaded inactive dead IPv6 firewall with ip6tables iptables.service loaded active exited IPv4 firewall with iptables irqbalance.service loaded active running irqbalance daemon kdump.service loaded active exited Crash recovery kernel arming kmod-static-nodes.service loaded active exited Create list of required static device nodes for the current kernel● ldap.service not-found inactive dead ldap.service● lvm2-activation.service not-found inactive dead lvm2-activation.service
开机启动：.service可以不写。
[root@lgs ~]# systemctl enable crond.service
检查是否开机启动：
[root@lgs ~]# systemctl is-enabled crondenabled
开机不启动：
[root@lgs ~]# systemctl disable crond.serviceRemoved symlink /etc/systemd/system/multi-user.target.wants/crond.service.[root@lgs ~]# systemctl is-enabled cronddisabled
查看服务状态：
[root@lgs ~]# systemctl status crond● crond.service - Command Scheduler Loaded: loaded (/usr/lib/systemd/system/crond.service; disabled; vendor preset: enabled) Active: active (running) since 日 2018-05-13 11:47:51 CST; 49min ago Main PID: 572 (crond) CGroup: /system.slice/crond.service └─572 /usr/sbin/crond -n5月 13 11:47:51 lgs systemd[1]: Started Command Scheduler.5月 13 11:47:51 lgs systemd[1]: Starting Command Scheduler...5月 13 11:47:51 lgs crond[572]: (CRON) INFO (RANDOM_DELAY will be scaled with factor 74% if used.)5月 13 11:47:51 lgs crond[572]: (CRON) INFO (running with inotify support)
单独开启、停止、重启服务：
[root@lgs ~]# systemctl stop crond[root@lgs ~]# systemctl start crond[root@lgs ~]# systemctl restart crond
如果一个服务设置开机启动后，会生成一个软链接文件：
如果设置开机不启动后，软链接文件就会被删除。
[root@lgs ~]# systemctl enable crondCreated symlink from /etc/systemd/system/multi-user.target.wants/crond.service to /usr/lib/systemd/system/crond.service.[root@lgs ~]# ls -l /etc/systemd/system/multi-user.target.wants/crond.service lrwxrwxrwx 1 root root 37 5月 13 12:40 /etc/systemd/system/multi-user.target.wants/crond.service -> /usr/lib/systemd/system/crond.service[root@lgs ~]# systemctl disable crondRemoved symlink /etc/systemd/system/multi-user.target.wants/crond.service.[root@lgs ~]# ls -l /etc/systemd/system/multi-user.target.wants/crond.service ls: 无法访问/etc/systemd/system/multi-user.target.wants/crond.service: 没有那个文件或目录
10.26 unit介绍
systemd开启和监督整个系统是基于unit的概念。unit是由一个与配置文件名同名的名字和类型组成的一个封装单元。
unit有很多类型： service：系统服务； target：多个unit组成的组； device：硬件设备；
mount：文件系统的挂载点； automount：自动挂载点； path：文件或者路径
scope：不是由systemd启动的外部进程； slice：进程组； snapshot：systemd 快照
socket：进程间通信的套接字； swap：swap文件； timer：定时器。
列出正在运行的unit：
[root@lgs ~]# systemctl list-units UNIT LOAD ACTIVE SUB DESCRIPTION proc-sys-fs-binfmt_misc.automount loaded active waiting Arbitrary Executable File Formats File System Automount Point sys-devices-pci0000:00-0000:00:07.1-ata2-host1-target1:0:0-1:0:0:0-block-sr0.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda1.device loaded active plugged VMware_Virtual_S 1 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda2.device loaded active plugged VMware_Virtual_S 2 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda3.device loaded active plugged VMware_Virtual_S 3 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda.device loaded active plugged VMware_Virtual_S sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb1.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX-YAIQ-30Xz-dqNz-TvZ6yS on sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb2.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW-kyY9-dHhy-6eIh-StZvVB on sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb3.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk-u3OE-PdET-rLAb-eyXCyd on sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb.device loaded active plugged VMware_Virtual_S sys-devices-pci0000:00-0000:00:11.0-0000:02:01.0-net-ens33.device loaded active plugged 82545EM Gigabit Ethernet Controller (Copper) (PRO/1000 MT Single P sys-devices-pci0000:00-0000:00:11.0-0000:02:02.0-sound-card0.device loaded active plugged ES1371/ES1373 / Creative Labs CT2518 (Audio PCI 64V/128/5200 / C sys-devices-platform-serial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1 sys-devices-platform-serial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2 sys-devices-platform-serial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3 sys-devices-pnp0-00:05-tty-ttyS0.device loaded active plugged /sys/devices/pnp0/00:05/tty/ttyS0 sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0 sys-module-configfs.device loaded active plugged /sys/module/configfs sys-subsystem-net-devices-ens33.device loaded active plugged 82545EM Gigabit Ethernet Controller (Copper) (PRO/1000 MT Single P -.mount loaded active mounted / boot.mount loaded active mounted /boot dev-hugepages.mount loaded active mounted Huge Pages File System dev-mqueue.mount loaded active mounted POSIX Message Queue File System run-user-0.mount loaded active mounted /run/user/0 sys-kernel-config.mount loaded active mounted Configuration File System sys-kernel-debug.mount loaded active mounted Debug File System brandbot.path loaded active waiting Flexible branding systemd-ask-password-plymouth.path loaded active waiting Forward Password Requests to Plymouth Directory Watch systemd-ask-password-wall.path loaded active waiting Forward Password Requests to Wall Directory Watch session-2.scope loaded active running Session 2 of user root auditd.service loaded active running Security Auditing Service chronyd.service loaded active running NTP client/server crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus getty@tty1.service loaded active running Getty on tty1 iptables.service loaded active exited IPv4 firewall with iptables irqbalance.service loaded active running irqbalance daemon kdump.service loaded active exited Crash recovery kernel arming kmod-static-nodes.service loaded active exited Create list of required static device nodes for the current kernel lvm2-lvmetad.service loaded active running LVM2 metadata daemon lvm2-monitor.service loaded active exited Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progr lvm2-pvscan@8:17.service loaded active exited LVM2 PV scan on device 8:17 lvm2-pvscan@8:18.service loaded active exited LVM2 PV scan on device 8:18 lvm2-pvscan@8:19.service loaded active exited LVM2 PV scan on device 8:19 mysqld.service loaded active running LSB: start and stop MySQL network.service loaded active exited LSB: Bring up/down networking NetworkManager-wait-online.service loaded active exited Network Manager Wait Online NetworkManager.service loaded active running Network Manager polkit.service loaded active running Authorization Manager postfix.service loaded active running Postfix Mail Transport Agent● rc-local.service loaded failed failed /etc/rc.d/rc.local Compatibility rhel-autorelabel-mark.service loaded active exited Mark the need to relabel after reboot rhel-dmesg.service loaded active exited Dump dmesg to /var/log/dmesg rhel-import-state.service loaded active exited Import network configuration from initramfs rhel-readonly.service loaded active exited Configure read-only root support rsyslog.service loaded active running System Logging Service sshd.service loaded active running OpenSSH server daemon sysstat.service loaded active exited Resets System Activity Logs systemd-journal-flush.service loaded active exited Flush Journal to Persistent Storage systemd-journald.service loaded active running Journal Service systemd-logind.service loaded active running Login Service systemd-random-seed.service loaded active exited Load/Save Random Seed systemd-remount-fs.service loaded active exited Remount Root and Kernel File Systems systemd-sysctl.service loaded active exited Apply Kernel Variables systemd-tmpfiles-setup-dev.service loaded active exited Create Static Device Nodes in /dev systemd-tmpfiles-setup.service loaded active exited Create Volatile Files and Directories systemd-udev-trigger.service loaded active exited udev Coldplug all Devices systemd-udevd.service loaded active running udev Kernel Device Manager systemd-update-utmp.service loaded active exited Update UTMP about System Boot/Shutdown systemd-user-sessions.service loaded active exited Permit User Sessions systemd-vconsole-setup.service loaded active exited Setup Virtual Console tuned.service loaded active running Dynamic System Tuning Daemon vgauthd.service loaded active running VGAuth Service for open-vm-tools vmtoolsd.service loaded active running Service for virtual machines hosted on VMware -.slice loaded active active Root Slice system-getty.slice loaded active active system-getty.slice system-lvm2\x2dpvscan.slice loaded active active system-lvm2\x2dpvscan.slice system-selinux\x2dpolicy\x2dmigrate\x2dlocal\x2dchanges.slice loaded active active system-selinux\x2dpolicy\x2dmigrate\x2dlocal\x2dchanges.slice system.slice loaded active active System Slice user-0.slice loaded active active User Slice of root user.slice loaded active active User and Session Slice dbus.socket loaded active running D-Bus System Message Bus Socket dm-event.socket loaded active listening Device-mapper event daemon FIFOs lvm2-lvmetad.socket loaded active running LVM2 metadata daemon socket lvm2-lvmpolld.socket loaded active listening LVM2 poll daemon 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 dev-disk-by\x2duuid-deb5a799\x2d817e\x2d41a2\x2d8ab5\x2d25893d3247b2.swap loaded active active /dev/disk/by-uuid/deb5a799-817e-41a2-8ab5-25893d3247b2 basic.target loaded active active Basic System cryptsetup.target loaded active active Encrypted Volumes getty.target loaded active active Login Prompts local-fs-pre.target loaded active active Local File Systems (Pre) local-fs.target loaded active active Local File Systems multi-user.target loaded active active Multi-User System network-online.target loaded active active Network is Online network.target loaded active active Network paths.target loaded active active Paths remote-fs.target loaded active active Remote File Systems slices.target loaded active active Slices sockets.target loaded active active Sockets sound.target loaded active active Sound Card swap.target loaded active active Swap sysinit.target loaded active active System Initialization timers.target loaded active active Timers systemd-tmpfiles-clean.timer loaded active waiting Daily Cleanup of Temporary DirectoriesLOAD = 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.108 loaded units listed. Pass --all to see loaded but inactive units, too.To show all installed unit files use 'systemctl list-unit-files'.lines 71-116/116 (END)
--all选项：列出所有的units，包括inactive、和失败的。
[root@lgs ~]# systemctl list-units --all UNIT LOAD ACTIVE SUB DESCRIPTION proc-sys-fs-binfmt_misc.automount loaded active waiting Arbitrary Executable File Formats File System Automount Point dev-block-8:17.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX-YAIQ-30Xz-dqNz-TvZ6yS on /dev/sdb1 1 dev-block-8:18.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW-kyY9-dHhy-6eIh-StZvVB on /dev/sdb2 2 dev-block-8:19.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk-u3OE-PdET-rLAb-eyXCyd on /dev/sdb3 3 dev-cdrom.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive dev-disk-by\x2did-ata\x2dVMware_Virtual_IDE_CDROM_Drive_10000000000000000001.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive dev-disk-by\x2did-dm\x2dname\x2dvg1\x2dlv1.device loaded active plugged /dev/disk/by-id/dm-name-vg1-lv1 dev-disk-by\x2did-dm\x2duuid\x2dLVM\x2d52fM6w9Z59cxCGS41hhRqVi76fnUmE3jJmFXe58h09mT5xXh1oFbU3dmL7OH1mU9.device loaded active plugged /dev/disk/by-id/ dev-disk-by\x2did-lvm\x2dpv\x2duuid\x2dDrJCcW\x2dNoZ3\x2d1zUk\x2du3OE\x2dPdET\x2drLAb\x2deyXCyd.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk- dev-disk-by\x2did-lvm\x2dpv\x2duuid\x2dEoP8W8\x2dB3x1\x2dV2FW\x2dkyY9\x2ddHhy\x2d6eIh\x2dStZvVB.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW- dev-disk-by\x2did-lvm\x2dpv\x2duuid\x2dm8V6a8\x2dxkMn\x2dW5tX\x2dYAIQ\x2d30Xz\x2ddqNz\x2dTvZ6yS.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX- dev-disk-by\x2dpath-pci\x2d0000:00:07.1\x2data\x2d2.0.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:0:0.device loaded active plugged VMware_Virtual_S dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:0:0\x2dpart1.device loaded active plugged VMware_Virtual_S 1 dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:0:0\x2dpart2.device loaded active plugged VMware_Virtual_S 2 dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:0:0\x2dpart3.device loaded active plugged VMware_Virtual_S 3 dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:1:0.device loaded active plugged VMware_Virtual_S dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:1:0\x2dpart1.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX-YAIQ-30Xz-dqNz-TvZ6yS on /de dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:1:0\x2dpart2.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW-kyY9-dHhy-6eIh-StZvVB on /de dev-disk-by\x2dpath-pci\x2d0000:00:10.0\x2dscsi\x2d0:0:1:0\x2dpart3.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk-u3OE-PdET-rLAb-eyXCyd on /de dev-disk-by\x2duuid-02635225\x2ddce3\x2d410a\x2d932d\x2d9e6d38fc22f3.device loaded active plugged /dev/disk/by-uuid/02635225-dce3-410a-932d-9e6d38fc2 dev-disk-by\x2duuid-9fa2450c\x2d5b1c\x2d4cd6\x2d99a0\x2d8c6baa0dc6f5.device loaded active plugged VMware_Virtual_S 1 dev-disk-by\x2duuid-deb5a799\x2d817e\x2d41a2\x2d8ab5\x2d25893d3247b2.device loaded active plugged VMware_Virtual_S 2 dev-disk-by\x2duuid-fefaab3f\x2d8726\x2d4a25\x2d9e55\x2dcea60b974233.device loaded active plugged VMware_Virtual_S 3 dev-dm\x2d0.device loaded active plugged /dev/dm-0 dev-mapper-vg1\x2dlv1.device loaded active plugged /dev/mapper/vg1-lv1 dev-sda.device loaded active plugged VMware_Virtual_S dev-sda1.device loaded active plugged VMware_Virtual_S 1 dev-sda2.device loaded active plugged VMware_Virtual_S 2 dev-sda3.device loaded active plugged VMware_Virtual_S 3 dev-sdb.device loaded active plugged VMware_Virtual_S dev-sdb1.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX-YAIQ-30Xz-dqNz-TvZ6yS on /dev/sdb1 1 dev-sdb2.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW-kyY9-dHhy-6eIh-StZvVB on /dev/sdb2 2 dev-sdb3.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk-u3OE-PdET-rLAb-eyXCyd on /dev/sdb3 3 dev-sr0.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive dev-ttyS0.device loaded active plugged /dev/ttyS0 dev-ttyS1.device loaded active plugged /dev/ttyS1 dev-ttyS2.device loaded active plugged /dev/ttyS2 dev-ttyS3.device loaded active plugged /dev/ttyS3 dev-vg1-lv1.device loaded active plugged /dev/vg1/lv1 sys-devices-pci0000:00-0000:00:07.1-ata2-host1-target1:0:0-1:0:0:0-block-sr0.device loaded active plugged VMware_Virtual_IDE_CDROM_Drive sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda1.device loaded active plugged VMware_Virtual_S 1 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda2.device loaded active plugged VMware_Virtual_S 2 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda-sda3.device loaded active plugged VMware_Virtual_S 3 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:0-2:0:0:0-block-sda.device loaded active plugged VMware_Virtual_S sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb1.device loaded active plugged LVM PV m8V6a8-xkMn-W5tX-YAIQ-30Xz-dqNz-TvZ6 sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb2.device loaded active plugged LVM PV EoP8W8-B3x1-V2FW-kyY9-dHhy-6eIh-StZv sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb-sdb3.device loaded active plugged LVM PV DrJCcW-NoZ3-1zUk-u3OE-PdET-rLAb-eyXC sys-devices-pci0000:00-0000:00:10.0-host2-target2:0:1-2:0:1:0-block-sdb.device loaded active plugged VMware_Virtual_S sys-devices-pci0000:00-0000:00:11.0-0000:02:01.0-net-ens33.device loaded active plugged 82545EM Gigabit Ethernet Controller (Copper) (PRO/1000 MT Sin sys-devices-pci0000:00-0000:00:11.0-0000:02:02.0-sound-card0.device loaded active plugged ES1371/ES1373 / Creative Labs CT2518 (Audio PCI 64V/128/520 sys-devices-platform-serial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1 sys-devices-platform-serial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2 sys-devices-platform-serial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3 sys-devices-pnp0-00:05-tty-ttyS0.device loaded active plugged /sys/devices/pnp0/00:05/tty/ttyS0 sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0 sys-module-configfs.device loaded active plugged /sys/module/configfs sys-subsystem-net-devices-ens33.device loaded active plugged 82545EM Gigabit Ethernet Controller (Copper) (PRO/1000 MT Sing -.mount loaded active mounted / boot.mount loaded active mounted /boot dev-hugepages.mount loaded active mounted Huge Pages File System dev-mqueue.mount loaded active mounted POSIX Message Queue File System proc-sys-fs-binfmt_misc.mount loaded inactive dead Arbitrary Executable File Formats File System run-user-0.mount loaded active mounted /run/user/0 sys-fs-fuse-connections.mount loaded inactive dead FUSE Control File System sys-kernel-config.mount loaded active mounted Configuration File System sys-kernel-debug.mount loaded active mounted Debug File System tmp.mount loaded inactive dead Temporary Directory brandbot.path loaded active waiting Flexible branding systemd-ask-password-console.path loaded inactive dead Dispatch Password Requests to Console Directory Watch systemd-ask-password-plymouth.path loaded active waiting Forward Password Requests to Plymouth Directory Watch systemd-ask-password-wall.path loaded active waiting Forward Password Requests to Wall Directory Watch session-2.scope loaded active running Session 2 of user root accounts-daemon.service loaded inactive dead Accounts Service auditd.service loaded active running Security Auditing Service brandbot.service loaded inactive dead Flexible Branding Service chronyd.service loaded active running NTP client/server cpupower.service loaded inactive dead Configure CPU power related settings crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus dm-event.service loaded inactive dead Device-mapper event daemon dracut-shutdown.service loaded inactive dead Restore /run/initramfs emergency.service loaded inactive dead Emergency Shell● exim.service not-found inactive dead exim.service gdm.service loaded inactive dead GNOME Display Manager getty@tty1.service loaded active running Getty on tty1 ip6tables.service loaded inactive dead IPv6 firewall with ip6tables iptables.service loaded active exited IPv4 firewall with iptables irqbalance.service loaded active running irqbalance daemon kdump.service loaded active exited Crash recovery kernel arming kmod-static-nodes.service loaded active exited Create list of required static device nodes for the current ke● ldap.service not-found inactive dead ldap.service● lvm2-activation.service not-found inactive dead lvm2-activation.service lvm2-lvmetad.service loaded active running LVM2 metadata daemon lvm2-lvmpolld.service loaded inactive dead LVM2 poll daemon lvm2-monitor.service loaded active exited Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or p lvm2-pvscan@8:17.service loaded active exited LVM2 PV scan on device 8:17 lvm2-pvscan@8:18.service loaded active exited LVM2 PV scan on device 8:18 lvm2-pvscan@8:19.service loaded active exited LVM2 PV scan on device 8:19 microcode.service loaded inactive dead Load CPU microcode update mysqld.service loaded active running LSB: start and stop MySQL network.service loaded active exited LSB: Bring up/down networking NetworkManager-wait-online.service loaded active exited Network Manager Wait Online NetworkManager.service loaded active running Network Manager● nscd.service not-found inactive dead nscd.service● ntpd.service not-found inactive dead ntpd.service● ntpdate.service not-found inactive dead ntpdate.service plymouth-quit-wait.service loaded inactive dead Wait for Plymouth Boot Screen to Quit plymouth-quit.service loaded inactive dead Terminate Plymouth Boot Screen plymouth-read-write.service loaded inactive dead Tell Plymouth To Write Out Runtime Data plymouth-start.service loaded inactive dead Show Plymouth Boot Screen polkit.service loaded active running Authorization Manager postfix.service loaded active running Postfix Mail Transport Agent● rc-local.service loaded failed failed /etc/rc.d/rc.local Compatibility
--state选项：指定状态
[root@lgs ~]# systemctl list-units --all --state=inactive UNIT LOAD ACTIVE SUB DESCRIPTION proc-sys-fs-binfmt_misc.mount loaded inactive dead Arbitrary Executable File Formats File System sys-fs-fuse-connections.mount loaded inactive dead FUSE Control File System tmp.mount loaded inactive dead Temporary Directory systemd-ask-password-console.path loaded inactive dead Dispatch Password Requests to Console Directory Watch accounts-daemon.service loaded inactive dead Accounts Service brandbot.service loaded inactive dead Flexible Branding Service cpupower.service loaded inactive dead Configure CPU power related settings dm-event.service loaded inactive dead Device-mapper event daemon dracut-shutdown.service loaded inactive dead Restore /run/initramfs emergency.service loaded inactive dead Emergency Shell● exim.service not-found inactive dead exim.service gdm.service loaded inactive dead GNOME Display Manager ip6tables.service loaded inactive dead IPv6 firewall with ip6tables● ldap.service not-found inactive dead ldap.service● lvm2-activation.service not-found inactive dead lvm2-activation.service lvm2-lvmpolld.service loaded inactive dead LVM2 poll daemon microcode.service loaded inactive dead Load CPU microcode update
--type选项：指定类型
[root@lgs ~]# systemctl list-units --all --type=service UNIT LOAD ACTIVE SUB DESCRIPTION accounts-daemon.service loaded inactive dead Accounts Service auditd.service loaded active running Security Auditing Service brandbot.service loaded inactive dead Flexible Branding Service chronyd.service loaded active running NTP client/server cpupower.service loaded inactive dead Configure CPU power related settings crond.service loaded active running Command Scheduler dbus.service loaded active running D-Bus System Message Bus dm-event.service loaded inactive dead Device-mapper event daemon dracut-shutdown.service loaded inactive dead Restore /run/initramfs emergency.service loaded inactive dead Emergency Shell● exim.service not-found inactive dead exim.service gdm.service loaded inactive dead GNOME Display Manager getty@tty1.service loaded active running Getty on tty1
查看指定服务是否激活：
[root@lgs ~]# systemctl is-active crondactive
10.27 target介绍
系统为了方便管理，用target来管理units
列出系统的target：
[root@lgs ~]# systemctl list-unit-files --type=targetUNIT FILE STATE basic.target static bluetooth.target static cryptsetup-pre.target static cryptsetup.target static ctrl-alt-del.target disableddefault.target enabled emergency.target static final.target static getty.target static graphical.target static halt.target disabledhibernate.target static hybrid-sleep.target static initrd-fs.target static initrd-root-fs.target static initrd-switch-root.target static initrd.target static iprutils.target disabledkexec.target disabledlocal-fs-pre.target static local-fs.target static machines.target disabledmulti-user.target enabled network-online.target static network-pre.target static network.target static nss-lookup.target static nss-user-lookup.target static paths.target static poweroff.target disabledprinter.target static reboot.target disabledremote-fs-pre.target static remote-fs.target enabled rescue.target disabledrpcbind.target static runlevel0.target disabledrunlevel1.target disabledrunlevel2.target enabled runlevel3.target enabled runlevel4.target enabled runlevel5.target static runlevel6.target disabledshutdown.target static sigpwr.target static sleep.target static slices.target static smartcard.target static sockets.target static sound.target static suspend.target static swap.target static sysinit.target static system-update.target static time-sync.target static timers.target static umount.target static 57 unit files listed.lines 15-60/60 (END)
查看指定target下有哪些units：
[root@lgs ~]# systemctl list-dependencies multi-user.targetmulti-user.target● ├─auditd.service● ├─brandbot.path● ├─chronyd.service● ├─crond.service● ├─dbus.service● ├─irqbalance.service● ├─kdump.service● ├─mysqld.service● ├─network.service● ├─NetworkManager.service● ├─plymouth-quit-wait.service● ├─plymouth-quit.service● ├─postfix.service● ├─rc-local.service● ├─rsyslog.service● ├─sshd.service● ├─sysstat.service● ├─systemd-ask-password-wall.path● ├─systemd-logind.service● ├─systemd-readahead-collect.service● ├─systemd-readahead-replay.service● ├─systemd-update-utmp-runlevel.service● ├─systemd-user-sessions.service● ├─tuned.service● ├─vmtoolsd.service● ├─basic.target● │ ├─iptables.service● │ ├─microcode.service● │ ├─rhel-autorelabel-mark.service● │ ├─rhel-autorelabel.service● │ ├─rhel-configure.service● │ ├─rhel-dmesg.service● │ ├─rhel-loadmodules.service● │ ├─selinux-policy-migrate-local-changes@targeted.service● │ ├─paths.target● │ ├─slices.target● │ │ ├─-.slice● │ │ └─system.slice● │ ├─sockets.target● │ │ ├─dbus.socket● │ │ ├─dm-event.socket● │ │ ├─systemd-initctl.socket● │ │ ├─systemd-journald.socket● │ │ ├─systemd-shutdownd.socket● │ │ ├─systemd-udevd-control.socket● │ │ └─systemd-udevd-kernel.socket● │ ├─sysinit.target● │ │ ├─dev-hugepages.mount● │ │ ├─dev-mqueue.mount● │ │ ├─kmod-static-nodes.service● │ │ ├─lvm2-lvmetad.socket● │ │ ├─lvm2-lvmpolld.socket● │ │ ├─lvm2-monitor.service● │ │ ├─plymouth-read-write.service● │ │ ├─plymouth-start.service● │ │ ├─proc-sys-fs-binfmt_misc.automount● │ │ ├─sys-fs-fuse-connections.mount● │ │ ├─sys-kernel-config.mount● │ │ ├─sys-kernel-debug.mount● │ │ ├─systemd-ask-password-console.path● │ │ ├─systemd-binfmt.service● │ │ ├─systemd-firstboot.service● │ │ ├─systemd-hwdb-update.service● │ │ ├─systemd-journal-catalog-update.service● │ │ ├─systemd-journal-flush.service● │ │ ├─systemd-journald.service● │ │ ├─systemd-machine-id-commit.service● │ │ ├─systemd-modules-load.service● │ │ ├─systemd-random-seed.service● │ │ ├─systemd-sysctl.service● │ │ ├─systemd-tmpfiles-setup-dev.service● │ │ ├─systemd-tmpfiles-setup.service● │ │ ├─systemd-udev-trigger.service● │ │ ├─systemd-udevd.service● │ │ ├─systemd-update-done.service● │ │ ├─systemd-update-utmp.service● │ │ ├─systemd-vconsole-setup.service● │ │ ├─cryptsetup.target● │ │ ├─local-fs.target● │ │ │ ├─-.mount● │ │ │ ├─boot.mount● │ │ │ ├─rhel-import-state.service● │ │ │ ├─rhel-readonly.service● │ │ │ └─systemd-remount-fs.service● │ │ └─swap.target● │ │ └─dev-disk-by\x2duuid-deb5a799\x2d817e\x2d41a2\x2d8ab5\x2d25893d3247b2.swap● │ └─timers.target● │ └─systemd-tmpfiles-clean.timer● ├─getty.target● │ └─getty@tty1.service● └─remote-fs.targetlines 47-92/92 (END)
target下可能含有其他target和service。
查看系统默认的target：
[root@lgs ~]# systemctl get-defaultmulti-user.target
设置系统默认的target：设置默认target，会创建一个软链接。
[root@lgs ~]# systemctl set-default multi-user.targetRemoved symlink /etc/systemd/system/default.target.Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.[root@lgs ~]# ls -l /etc/systemd/system/default.targetlrwxrwxrwx 1 root root 41 5月 13 13:41 /etc/systemd/system/default.target -> /usr/lib/systemd/system/multi-user.target
查看一个service是属于哪个target的：[Install]部分的WantedBy
[root@lgs ~]# cat /usr/lib/systemd/system/sshd.service [Unit]Description=OpenSSH server daemonDocumentation=man:sshd(8) man:sshd_config(5)After=network.target sshd-keygen.serviceWants=sshd-keygen.service[Service]Type=notifyEnvironmentFile=/etc/sysconfig/sshdExecStart=/usr/sbin/sshd -D $OPTIONSExecReload=/bin/kill -HUP $MAINPIDKillMode=processRestart=on-failureRestartSec=42s[Install]WantedBy=multi-user.target
multi-user.target下的service才能设置开机启动。