系统结构

system 运行 roslaunch system destroy_linux


Systemd 的设计目标是为系统的启动和管理提供一套完整的解决方案，具体的结构如上图所示。Systtemd不是一个命令，而是一组命令，这组命令涉及系统管理的多个方面。

Systemd的相关命令

systemctl

#查看版本
$ sudo systemctl --version

# 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

# 让系统进入休眠状态
$ 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

systemctl 子命令大全

Unit Commands:
  list-units [PATTERN...]             List units currently in memory
  list-sockets [PATTERN...]           List socket units currently in memory,
                                      ordered by address
  list-timers [PATTERN...]            List timer units currently in memory,
                                      ordered by next elapse
  start UNIT...                       Start (activate) one or more units
  stop UNIT...                        Stop (deactivate) one or more units
  reload UNIT...                      Reload one or more units
  restart UNIT...                     Start or restart one or more units
  try-restart UNIT...                 Restart one or more units if active
  reload-or-restart UNIT...           Reload one or more units if possible,
                                      otherwise start or restart
  try-reload-or-restart UNIT...       If active, reload one or more units,
                                      if supported, otherwise restart
  isolate UNIT                        Start one unit and stop all others
  kill UNIT...                        Send signal to processes of a unit
  clean UNIT...                       Clean runtime, cache, state, logs or
                                      configuration of 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 specified units
  set-property UNIT PROPERTY=VALUE... 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 [UNIT...]         Recursively show units which are required
                                      or wanted by the units or by which those
                                      units are required or wanted
Unit File Commands:
  list-unit-files [PATTERN...]        List installed unit files
  enable [UNIT...|PATH...]            Enable one or more unit files
  disable UNIT...                     Disable one or more unit files
  reenable UNIT...                    Reenable one or more unit files
  preset UNIT...                      Enable/disable one or more unit files
                                      based on preset configuration
  preset-all                          Enable/disable all unit files based on
                                      preset configuration
  is-enabled UNIT...                  Check whether unit files are enabled
  mask UNIT...                        Mask one or more units
  unmask UNIT...                      Unmask one or more units
  link PATH...                        Link one or more units files into
                                      the search path
  revert UNIT...                      Revert one or more unit files to vendor
                                      version
  add-wants TARGET UNIT...            Add 'Wants' dependency for the target
                                      on specified one or more units
  add-requires TARGET UNIT...         Add 'Requires' dependency for the target
                                      on specified one or more units
  edit UNIT...                        Edit one or more unit files
  get-default                         Get the name of the default target
  set-default TARGET                  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

Environment Commands:
  show-environment                    Dump environment
  set-environment VARIABLE=VALUE...   Set one or more environment variables
  unset-environment VARIABLE...       Unset one or more environment variables
  import-environment [VARIABLE...]    Import all or some environment variables

Manager State Commands:
  daemon-reload                       Reload systemd manager configuration
  daemon-reexec                       Reexecute systemd manager
  log-level [LEVEL]                   Get/set logging threshold for manager
  log-target [TARGET]                 Get/set logging target for manager
  service-watchdogs [BOOL]            Get/set service watchdog state

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 [EXIT_CODE]                    Request user instance or container 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
  suspend-then-hibernate              Suspend the system, wake after a period of
                                      time, and hibernate

system 运行 roslaunch system destroy_运维_02

systemd-analyze

# 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

system 运行 roslaunch system destroy_List_03


system 运行 roslaunch system destroy_system 运行 roslaunch_04


system 运行 roslaunch system destroy_运维_05

hosnametctl

# 显示当前主机的信息
$ hostnamectl

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

system 运行 roslaunch system destroy_system 运行 roslaunch_06

localectl

# 查看本地化设置
$ localectl

# 设置本地化参数。
$ sudo localectl set-locale LANG=en_GB.utf8
$ sudo localectl set-keymap en_GB

system 运行 roslaunch system destroy_linux_07

timedatectl

# 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

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loginctl

#查看当前登录的用户
$ loginctl

system 运行 roslaunch system destroy_List_09

journalctl

管理日志的命令

# 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）
$ sudo journalctl -k

# 查看系统本次启动的日志
$ 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
$ sudo journalctl -n

# 显示尾部指定行数的日志
$ sudo journalctl -n 20

# 实时滚动显示最新日志
$ sudo journalctl -f

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

# 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

如：

system 运行 roslaunch system destroy_centos_10


system 运行 roslaunch system destroy_List_11