[Unit]	
Description=Hello World	
After=docker.service	
Requires=docker.service	
[Service]	
TimeoutStartSec=0	
ExecStartPre=-/usr/bin/docker kill busybox1	
ExecStartPre=-/usr/bin/docker rm busybox1	
ExecStartPre=/usr/bin/docker pull busybox	
ExecStart=/usr/bin/docker run --name busybox1 busybox /bin/ sh -c "while true; do echo Hello World; sleep 1; done"	
ExecStop="/usr/bin/docker stop busybox1"	
ExecStopPost="/usr/bin/docker rm busybox1"	
[Install]	
WantedBy=multi-user.target

# find /etc/systemd/system/* -type d	
/etc/systemd/system/default.target.wants	
/etc/systemd/system/getty.target.wants	
/etc/systemd/system/graphical.target.wants	
/etc/systemd/system/multi-user.target.wants	
/etc/systemd/system/network-online.target.wants	
/etc/systemd/system/paths.target.wants	
/etc/systemd/system/shutdown.target.wants	
/etc/systemd/system/sockets.target.wants	
/etc/systemd/system/sysinit.target.wants	
/etc/systemd/system/timers.target.wants

# systemctl list-units --type=target	
UNIT                   LOAD   ACTIVE SUB    DESCRIPTION	
basic.target           loaded active active Basic System	
cryptsetup.target      loaded active active Encrypted Volumes	
getty.target           loaded active active Login Prompts	
graphical.target       loaded active active Graphical Interface	
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	
nss-user-lookup.target loaded active active User and Group Name Lookups	
paths.target           loaded active active Paths	
remote-fs-pre.target   loaded active active Remote File Systems (Pre)	
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	
time-sync.target       loaded active active System Time Synchronized	
timers.target          loaded active active Timers	
LOAD   = Reflects whether the unit definition was properly loaded.	
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.	
SUB    = The low-level unit activation state, values depend on unit type.	
20 loaded units listed. Pass --all to see loaded but inactive units, too.	
To show all installed unit files use 'systemctl list-unit-files'.

[Unit]	
Description=My Advanced Service Template	
After=etcd.service docker.service	
[Service]	
TimeoutStartSec=0	
ExecStartPre=-/usr/bin/docker kill apache%i	
ExecStartPre=-/usr/bin/docker rm apache%i	
ExecStartPre=/usr/bin/docker pull coreos/apache	
ExecStart=/usr/bin/docker run --name apache%i -p %i:80 coreos/apache /usr/sbin/apache2ctl -D FOREGROUND	
ExecStartPost=/usr/bin/etcdctl set /domains/example.com/%H:%i running	
ExecStop=/usr/bin/docker stop apache1	
ExecStopPost=/usr/bin/docker rm apache1	
ExecStopPost=/usr/bin/etcdctl rm /domains/example.com/%H:%i	
[Install]	
WantedBy=multi-user.target

# systemctl start apache@8080.service

# systemctl --help	
systemctl [OPTIONS...] {COMMAND} ...	
Query or send control commands to the systemd manager.	
  -h --help           Show this help	
     --version        Show package version	
     --system         Connect to system manager	
  -H --host=[USER@]HOST	
                      Operate on remote host	
  -M --machine=CONTAINER	
                      Operate on local container	
  -t --type=TYPE      List units of a particular type	
     --state=STATE    List units with particular LOAD or SUB or ACTIVE state	
  -p --property=NAME  Show only properties by this name	
  -a --all            Show all loaded units/properties, including dead/empty	
                      ones. To list all units installed on the system, use	
                      the 'list-unit-files' command instead.	
  -l --full           Don't ellipsize unit names on output	
  -r --recursive      Show unit list of host and local containers	
     --reverse        Show reverse dependencies with 'list-dependencies'	
     --job-mode=MODE  Specify how to deal with already queued jobs, when	
                      queueing a new job	
     --show-types     When showing sockets, explicitly show their type	
  -i --ignore-inhibitors	
                      When shutting down or sleeping, ignore inhibitors	
     --kill-who=WHO   Who to send signal to	
  -s --signal=SIGNAL  Which signal to send	
     --now            Start or stop unit in addition to enabling or disabling it	
  -q --quiet          Suppress output	
     --no-block       Do not wait until operation finished	
     --no-wall        Don't send wall message before halt/power-off/reboot	
     --no-reload      Don't reload daemon after en-/dis-abling unit files	
     --no-legend      Do not print a legend (column headers and hints)	
     --no-pager       Do not pipe output into a pager	
     --no-ask-password	
                      Do not ask for system passwords	
     --global         Enable/disable unit files globally	
     --runtime        Enable unit files only temporarily until next reboot	
  -f --force          When enabling unit files, override existing symlinks	
                      When shutting down, execute action immediately	
     --preset-mode=   Apply only enable, only disable, or all presets	
     --root=PATH      Enable unit files in the specified root directory	
  -n --lines=INTEGER  Number of journal entries to show	
  -o --output=STRING  Change journal output mode (short, short-iso,	
                              short-precise, short-monotonic, verbose,	
                              export, json, json-pretty, json-sse, cat)	
     --plain          Print unit dependencies as a list instead of a tree	
Unit Commands:	
  list-units [PATTERN...]         List loaded units	
  list-sockets [PATTERN...]       List loaded sockets ordered by address	
  list-timers [PATTERN...]        List loaded timers ordered by next elapse	
  start NAME...                   Start (activate) one or more units	
  stop NAME...                    Stop (deactivate) one or more units	
  reload NAME...                  Reload one or more units	
  restart NAME...                 Start or restart one or more units	
  try-restart NAME...             Restart one or more units if active	
  reload-or-restart NAME...       Reload one or more units if possible,	
                                  otherwise start or restart	
  reload-or-try-restart NAME...   Reload one or more units if possible,	
                                  otherwise restart if active	
  isolate NAME                    Start one unit and stop all others	
  kill NAME...                    Send signal to processes of a unit	
  is-active PATTERN...            Check whether units are active	
  is-failed PATTERN...            Check whether units are failed	
  status [PATTERN...|PID...]      Show runtime status of one or more units	
  show [PATTERN...|JOB...]        Show properties of one or more	
                                  units/jobs or the manager	
  cat PATTERN...                  Show files and drop-ins of one or more units	
  set-property NAME ASSIGNMENT... Sets one or more properties of a unit	
  help PATTERN...|PID...          Show manual for one or more units	
  reset-failed [PATTERN...]       Reset failed state for all, one, or more	
                                  units	
  list-dependencies [NAME]        Recursively show units which are required	
                                  or wanted by this unit or by which this	
                                  unit is required or wanted	
Unit File Commands:	
  list-unit-files [PATTERN...]    List installed unit files	
  enable NAME...                  Enable one or more unit files	
  disable NAME...                 Disable one or more unit files	
  reenable NAME...                Reenable one or more unit files	
  preset NAME...                  Enable/disable one or more unit files	
                                  based on preset configuration	
  preset-all                      Enable/disable all unit files based on	
                                  preset configuration	
  is-enabled NAME...              Check whether unit files are enabled	
  mask NAME...                    Mask one or more units	
  unmask NAME...                  Unmask one or more units	
  link PATH...                    Link one or more units files into	
                                  the search path	
  add-wants TARGET NAME...        Add 'Wants' dependency for the target	
                                  on specified one or more units	
  add-requires TARGET NAME...     Add 'Requires' dependency for the target	
                                  on specified one or more units	
  edit NAME...                    Edit one or more unit files	
  get-default                     Get the name of the default target	
  set-default NAME                Set the default target	
Machine Commands:	
  list-machines [PATTERN...]      List local containers and host	
Job Commands:	
  list-jobs [PATTERN...]          List jobs	
  cancel [JOB...]                 Cancel all, one, or more jobs	
Snapshot Commands:	
  snapshot [NAME]                 Create a snapshot	
  delete NAME...                  Remove one or more snapshots	
Environment Commands:	
  show-environment                Dump environment	
  set-environment NAME=VALUE...   Set one or more environment variables	
  unset-environment NAME...       Unset one or more environment variables	
  import-environment [NAME...]    Import all or some environment variables	
Manager Lifecycle Commands:	
  daemon-reload                   Reload systemd manager configuration	
  daemon-reexec                   Reexecute systemd manager	
System Commands:	
  is-system-running               Check whether system is fully running	
  default                         Enter system default mode	
  rescue                          Enter system rescue mode	
  emergency                       Enter system emergency mode	
  halt                            Shut down and halt the system	
  poweroff                        Shut down and power-off the system	
  reboot [ARG]                    Shut down and reboot the system	
  kexec                           Shut down and reboot the system with kexec	
  exit                            Request user instance exit	
  switch-root ROOT [INIT]         Change to a different root file system	
  suspend                         Suspend the system	
  hibernate                       Hibernate the system	
  hybrid-sleep                    Hibernate and suspend the system

# 列出正在运行的 Unit	
$ systemctl list-units	

	
# 列出所有Unit，包括没有找到配置文件的或者启动失败的	
$ systemctl list-units --all	

	
# 列出所有没有运行的 Unit	
$ systemctl list-units --all --state=inactive	

	
# 列出所有加载失败的 Unit	
$ systemctl list-units --failed	

	
# 列出所有正在运行的、类型为 service 的 Unit	
$ systemctl list-units --type=service	

	
# 查看 Unit 配置文件的内容	
$ systemctl cat docker.service

# 显示系统状态	
$ systemctl status	

	
# 显示单个 Unit 的状态	
$ ystemctl status bluetooth.service	

	
# 显示远程主机的某个 Unit 的状态	
$ systemctl -H root@rhel7.example.com status httpd.service

# 立即启动一个服务	
$ sudo systemctl start apache.service	

	
# 立即停止一个服务	
$ sudo systemctl stop apache.service	

	
# 重启一个服务	
$ sudo systemctl restart apache.service	

	
# 杀死一个服务的所有子进程	
$ sudo systemctl kill apache.service	

	
# 重新加载一个服务的配置文件	
$ sudo systemctl reload apache.service	

	
# 重载所有修改过的配置文件	
$ sudo systemctl daemon-reload	

	
# 显示某个 Unit 的所有底层参数	
$ systemctl show httpd.service	

	
# 显示某个 Unit 的指定属性的值	
$ systemctl show -p CPUShares httpd.service	

	
# 设置某个 Unit 的指定属性	
$ sudo systemctl set-property httpd.service CPUShares=500

# 列出一个 Unit 的所有依赖，默认不会列出 target 类型	
$ systemctl list-dependencies nginx.service	

	
# 列出一个 Unit 的所有依赖，包括 target 类型	
$ systemctl list-dependencies --all nginx.service

# 查看当前系统的所有 Target	
$ systemctl list-unit-files --type=target	

	
# 查看一个 Target 包含的所有 Unit	
$ systemctl list-dependencies multi-user.target	

	
# 查看启动时的默认 Target	
$ systemctl get-default	

	
# 设置启动时的默认 Target	
$ sudo systemctl set-default multi-user.target	

	
# 切换 Target 时，默认不关闭前一个 Target 启动的进程，systemctl isolate 命令改变这种行为，关闭前一个 Target 里面所有不属于后一个 Target 的进程	
$ sudo systemctl isolate multi-user.target

# 查看所有日志（默认情况下 ，只保存本次启动的日志）	
$ sudo journalctl	

	
# 查看内核日志（不显示应用日志）：--dmesg 或 -k	
$ sudo journalctl -k	

	
# 查看系统本次启动的日志（其中包括了内核日志和各类系统服务的控制台输出）：--system 或 -b	
$ sudo journalctl -b	
$ sudo journalctl -b -0	

	
# 查看上一次启动的日志（需更改设置）	
$ sudo journalctl -b -1	

	
# 查看指定服务的日志：--unit 或 -u	
$ sudo journalctl -u docker.servcie	

	
# 查看指定服务的日志	
$ sudo journalctl /usr/lib/systemd/systemd	

	
# 实时滚动显示最新日志	
$ sudo journalctl -f	

	
# 查看指定时间的日志	
$ sudo journalctl --since="2012-10-30 18:17:16"	
$ sudo journalctl --since "20 min ago"	
$ sudo journalctl --since yesterday	
$ sudo journalctl --since "2015-01-10" --until "2015-01-11 03:00"	
$ sudo journalctl --since 09:00 --until "1 hour ago"	

	
# 显示尾部的最新 10 行日志：--lines 或 -n	
$ sudo journalctl -n	

	
# 显示尾部指定行数的日志	
$ sudo journalctl -n 20	

	
# 将最新的日志显示在前面	
$ sudo journalctl -r -u docker.service	

	
# 改变输出的格式：--output 或 -o	
$ sudo journalctl -r -u docker.service -o json-pretty	

	
# 查看指定进程的日志	
$ sudo journalctl _PID=1	

	
# 查看某个路径的脚本的日志	
$ sudo journalctl /usr/bin/bash	

	
# 查看指定用户的日志	
$ sudo journalctl _UID=33 --since today	

	
# 查看某个 Unit 的日志	
$ sudo journalctl -u nginx.service	
$ sudo journalctl -u nginx.service --since today	

	
# 实时滚动显示某个 Unit 的最新日志	
$ sudo journalctl -u nginx.service -f	

	
# 合并显示多个 Unit 的日志	
$ journalctl -u nginx.service -u php-fpm.service --since today	

	
# 查看指定优先级（及其以上级别）的日志，共有 8 级	
# 0: emerg	
# 1: alert	
# 2: crit	
# 3: err	
# 4: warning	
# 5: notice	
# 6: info	
# 7: debug	
$ sudo journalctl -p err -b	

	
# 日志默认分页输出，--no-pager 改为正常的标准输出	
$ sudo journalctl --no-pager	

	
# 以 JSON 格式（单行）输出	
$ sudo journalctl -b -u nginx.service -o json	

	
# 以 JSON 格式（多行）输出，可读性更好	
$ sudo journalctl -b -u nginx.serviceqq	
 -o json-pretty	

	
# 显示日志占据的硬盘空间	
$ sudo journalctl --disk-usage	

	
# 指定日志文件占据的最大空间	
$ sudo journalctl --vacuum-size=1G	

	
# 指定日志文件保存多久	
$ sudo journalctl --vacuum-time=1years

# 重启系统	
$ sudo systemctl reboot	

	
# 关闭系统，切断电源	
$ sudo systemctl poweroff	

	
# CPU停止工作	
$ sudo systemctl halt	

	
# 暂停系统	
$ sudo systemctl suspend	

	
# 让系统进入冬眠状态	
$ sudo systemctl hibernate	

	
# 让系统进入交互式休眠状态	
$ sudo systemctl hybrid-sleep	

	
# 启动进入救援状态（单用户状态）	
$ sudo systemctl rescue

# 查看启动耗时	
$ systemd-analyze	

	
# 查看每个服务的启动耗时	
$ systemd-analyze blame	

	
# 显示瀑布状的启动过程流	
$ systemd-analyze critical-chain	

	
# 显示指定服务的启动流	
$ systemd-analyze critical-chain atd.service

# 显示当前主机的信息	
$ hostnamectl	

	
# 设置主机名。	
$ sudo hostnamectl set-hostname rhel7

# 查看当前时区设置	
$ timedatectl	

	
# 显示所有可用的时区	
$ timedatectl list-timezones	

	
# 设置当前时区	
$ sudo timedatectl set-timezone America/New_York	
$ sudo timedatectl set-time YYYY-MM-DD	
$ sudo timedatectl set-time HH:MM:SS

# 列出当前 session	
$ loginctl list-sessions	

	
# 列出当前登录用户	
$ loginctl list-users	

	
# 列出显示指定用户的信息	
$ loginctl show-user ruanyf

$ PASSWORD=$(systemd-ask-password "Input Your Passowrd:")