linux系统运行级别
Centos, Ubuntu系统运行级别、开机启动脚本的说明
Linux系统运行级别
| Centos 运行级别 | target信息 | 说明 |
|---|---|---|
| 0 | poweroff.target | 系统停机状态，系统默认运行级别不能设为0，否则不能正常启动 |
| 1, S | rescue.target | 单用户工作状态，只有root可以login，用于系统修复，重置密码信息, 没有网络, 禁止远程登陆 |
| 2 | multi-user.target | 状态(没有NFS), 没有网络 |
| 3 | multi-user.target | 完全的多用户状态(有NFS)，登陆后进入控制台命令行模式, 有网络 |
| 4 | multi-user.target | 系统未使用，保留 |
| 5 | graphical.target | X11控制台，登陆后进入图形GUI模式 |
| 6 | reboot.target | 系统正常关闭并重启，默认运行级别不能设为6，否则不能正常启动 |
查看运行级别:
$ runlevel
$ systemctl get-default
查看target以及依赖independency信息
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**查看可用target****
除了以上的运行级别外, linux系统还提供了70多种额外的targets, 大多数是以上5种级别的子集
**daniel@daniel-lib-ubuntu:~$ systemctl list-units --type=target **
daniel@daniel-lib-ubuntu:~$ systemctl list-units --type=target
UNIT LOAD ACTIVE SUB DESCRIPTION
basic.target loaded active active Basic System
cryptsetup.target loaded active active Local 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-lookup.target loaded active active Host and Network Name Lookups
nss-user-lookup.target loaded active active User and Group Name Lookups
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
swap.target loaded active active Swap
sysinit.target loaded active active System Initialization
time-set.target loaded active active System Time Set
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'.
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查看target需要的依赖服务
daniel@daniel-lib-ubuntu:~$ systemctl list-dependencies multi-user.target
绿点: service 或 target 处于运行(running)或活跃(active)状态
白点: service 或 target 处于非活跃状态(inactive or dead)
红点: service 或 target 启动失败或有致命错误
list-dependencies.png
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查询runlevels对应的targets
daniel@daniel-lib-ubuntu:~$ ls -l /usr/lib/systemd/system/runlevel{0..6}.target
daniel@daniel-lib-ubuntu:~$ ls -l /usr/lib/systemd/system/runlevel*target
lrwxrwxrwx 1 root root 15 Jan 7 04:47 /usr/lib/systemd/system/runlevel0.target -> poweroff.target
lrwxrwxrwx 1 root root 13 Jan 7 04:47 /usr/lib/systemd/system/runlevel1.target -> rescue.target
lrwxrwxrwx 1 root root 17 Jan 7 04:47 /usr/lib/systemd/system/runlevel2.target -> multi-user.target
lrwxrwxrwx 1 root root 17 Jan 7 04:47 /usr/lib/systemd/system/runlevel3.target -> multi-user.target
lrwxrwxrwx 1 root root 17 Jan 7 04:47 /usr/lib/systemd/system/runlevel4.target -> multi-user.target
lrwxrwxrwx 1 root root 16 Jan 7 04:47 /usr/lib/systemd/system/runlevel5.target -> graphical.target
lrwxrwxrwx 1 root root 13 Jan 7 04:47 /usr/lib/systemd/system/runlevel6.target -> reboot.target
临时调整runlevel级别:
init 3
telinit 3
systemctl isolate multi-user.target #isolate 动态改变对应target: 开启对应级别依赖,并立即停止新级别中不会使用的进程 参考 man systemctl
永久设置runlevel级别
centos 6
vim /etc/inittab
centos 7 , ubuntu
systemctl set-default multi-user.target
ubuntu自启动脚本目录/文件
daniel@daniel-lib-ubuntu:~$ ll /etc |grep rc..d
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc0.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc1.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc2.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc3.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc4.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc5.d/
drwxr-xr-x 2 root root 4096 Mar 31 20:58 rc6.d/
drwxr-xr-x 2 root root 4096 Jul 30 2020 rcS.d/
lrwxrwxrwx 1 root root 27 Jul 30 2020 K01speech-dispatcher -> ../init.d/speech-dispatcher*
lrwxrwxrwx 1 root root 15 Jul 30 2020 S01acpid -> ../init.d/acpid*
lrwxrwxrwx 1 root root 17 Jul 30 2020 S01anacron -> ../init.d/anacron*
lrwxrwxrwx 1 root root 16 Jul 30 2020 S01apport -> ../init.d/apport*
lrwxrwxrwx 1 root root 22 Jul 30 2020 S01avahi-daemon -> ../init.d/avahi-daemon*
lrwxrwxrwx 1 root root 19 Jul 30 2020 S01bluetooth -> ../init.d/bluetooth*
lrwxrwxrwx 1 root root 26 Jul 30 2020 S01console-setup.sh -> ../init.d/console-setup.sh*
lrwxrwxrwx 1 root root 14 Jul 30 2020 S01cron -> ../init.d/cron*
说明:
rc.0.d~rc.t6.d , rcS.d对应系统0-6个运行状态需要执行的脚本, 目录下的每个文件都是/etc/init.d/目录下文件的一个软链接, 命名规则为K+nn+服务名或S+nn+服务名，其中nn为两位数字
/etc/init.d/ 目录存放了所有开机自启动脚本
K, S 为init.d下的脚本传递了参数, K 传递 stop, S传递 start , 可以看到rc0.d中全部文件都以K开头.停止了所有服, 实现了关机
K, S后的数字 用来决定脚本执行顺序(从小到大)
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关于没有/etc/rc.local 文件: Ubuntu 16.04 版本开始去除了 rc.local 文件，自启动服务方面基本由 systemd 全面接管
实际上Ubuntu20.04 存在rc-local.service文件 位置为: /lib/systemd/system/rc-local.service, 用户可以自行创建rc.local
步骤如下:
$sudo vim /etc/rc.local#!/bin/sh # 这里添加要开机执行的脚本和命令等等 exit 0-
添加执行权限
$ sudo chmod +x /etc/rc.local -
创建软链接
$ sudo ln -s /lib/systemd/system/rc-local.service /etc/systemd/system/rc-local.service 重启系统使rc.local生效
参考:
https://blog.csdn.net/qq_41782149/article/details/89001226
https://www.answertopia.com/ubuntu/managing-ubuntu-systemd-units/
