Linux系统重要文件(三)
一系统运行级别文件
文件路径:/etc/inittab
文件作用说明:定义系统启动后,自动开启哪些软件程序系统
runlevel 查看当前运行级别
centos6系统运行级别: 7个级别
0 -- 系统关机级别 init 0
1 -- 系统单用户级别
用于破解系统密码root,救援恢复系统数据,没有网络服务
2 -- 系统多用户级别 没有网络多用户级别
3 -- 系统多用户级别 拥有网络多用户级别,生产中使用最多
4 -- 未使用级别
5 -- 系统图形化级别
6 -- 系统重启级别 init 6
(一)查看当前运行级别
- [root@centos61 ~]# cat /etc/redhat-release
- CentOS release 6.8 (Final)
- [root@centos61 ~]# runlevel
- N
- [root@centos71 ~]# cat /etc/redhat-release
- CentOS Linux release 7.6. (Core)
- [root@centos71 ~]# runlevel
- N
(二)centos6设置系统级别
临时设置:init 级别数字
- [root@centos61 ~]# cat /etc/inittab
- # inittab is only used by upstart for the default runlevel.
- #
- # ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
- #
- # System initialization is started by /etc/init/rcS.conf
- #
- # Individual runlevels are started by /etc/init/rc.conf
- #
- # Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf
- #
- # Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,
- # with configuration in /etc/sysconfig/init.
- #
- # For information on how to write upstart event handlers, or how
- # upstart works, see init(), init(), and initctl().
- #
- # Default runlevel. The runlevels used are:
- # - halt (Do NOT set initdefault to this)
- # - Single user mode
- # - Multiuser, without NFS (The same as , if you do not have networking)
- # - Full multiuser mode
- # - unused
- # - X11
- # - reboot (Do NOT set initdefault to this)
- #
- id::initdefault:
此时断开远程连接
- [root@centos61 ~]# init
- [root@centos61 ~]#
- Connection closed by foreign host.
- Disconnected from remote host(centos61) at ::.
- Type `help' to learn how to use Xshell prompt.
- [c:\~]$
永久设置
对配置文件/etc/inittab修改
可以使用小工具进行修改,比如sed,awk,强化练习
- [root@centos61 ~]# sed -i s/::/::/g /etc/inittab
- [root@centos61 ~]# tail - /etc/inittab
- id::initdefault:
- [root@centos61 ~]# runlevel
- S
- [root@centos61 ~]# reboot
- Broadcast message from root@centos61.huawei.com
- (/dev/pts/) at : ...
- The system is going down for reboot NOW!
- [root@centos61 ~]#
- Connection closed by foreign host.
- Disconnected from remote host(centos6-) at ::.
- Type `help' to learn how to use Xshell prompt.
注意还要执行init 3才可以的
- [root@centos61 ~]# runlevel
- S
(三)centos7设置系统级别
和centos6有区别,使用target模式
- [root@centos7 ~]# ll /usr/lib/systemd/system/runlevel*target
- lrwxrwxrwx. 1 root root 15 Nov 26 17:33 /usr/lib/systemd/system/runlevel0.target -> poweroff.target
- lrwxrwxrwx. 1 root root 13 Nov 26 17:33 /usr/lib/systemd/system/runlevel1.target -> rescue.target
- lrwxrwxrwx. 1 root root 17 Nov 26 17:33 /usr/lib/systemd/system/runlevel2.target -> multi-user.target
- lrwxrwxrwx. 1 root root 17 Nov 26 17:33 /usr/lib/systemd/system/runlevel3.target -> multi-user.target
- lrwxrwxrwx. 1 root root 17 Nov 26 17:33 /usr/lib/systemd/system/runlevel4.target -> multi-user.target
- lrwxrwxrwx. 1 root root 16 Nov 26 17:33 /usr/lib/systemd/system/runlevel5.target -> graphical.target
- lrwxrwxrwx. 1 root root 13 Nov 26 17:33 /usr/lib/systemd/system/runlevel6.target -> reboot.target
- [root@centos7 ~]# runlevel
- N
- [root@centos71 ~]# ll /usr/lib/systemd/system/multi-user.target
- -rw-r--r--. root root Oct /usr/lib/systemd/system/multi-user.target
- [root@centos71 ~]# ll /usr/lib/systemd/system/rescue.target
- -rw-r--r--. root root Oct /usr/lib/systemd/system/rescue.target
- [root@centos71 ~]# cat /usr/lib/systemd/system/multi-user.target
- # This file is part of systemd.
- #
- # systemd is free software; you can redistribute it and/or modify it
- # under the terms of the GNU Lesser General Public License as published by
- # the Free Software Foundation; either version 2.1 of the License, or
- # (at your option) any later version.
- [Unit]
- Description=Multi-User System
- Documentation=man:systemd.special()
- Requires=basic.target
- Conflicts=rescue.service rescue.target
- After=basic.target rescue.service rescue.target
- AllowIsolate=yes
- [root@centos71 ~]# cat /usr/lib/systemd/system/rescue.target
- # This file is part of systemd.
- #
- # systemd is free software; you can redistribute it and/or modify it
- # under the terms of the GNU Lesser General Public License as published by
- # the Free Software Foundation; either version 2.1 of the License, or
- # (at your option) any later version.
- [Unit]
- Description=Rescue Mode
- Documentation=man:systemd.special()
- Requires=sysinit.target rescue.service
- After=sysinit.target rescue.service
- AllowIsolate=yes
- [Install]
- Alias=kbrequest.target
临时设置: init 级别数字
永久设置
- [root@centos71 ~]# cat /etc/inittab
- # inittab is no longer used when using systemd.
- #
- # ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
- #
- # Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
- #
- # systemd uses 'targets' instead of runlevels. By default, there are two main targets:
- #
- # multi-user.target: analogous to runlevel
- # graphical.target: analogous to runlevel
- #
- # To view current default target, run:
- # systemctl get-default
- #
- # To set a default target, run:
- # systemctl set-default TARGET.target



二系统登录前后提示文件
(一)登录系统前显示提示信息
- [root@centos71 ~]# ll /etc/issue*
- -rw-r--r--. root root Nov /etc/issue
- -rw-r--r--. root root Nov /etc/issue.net
- [root@centos71 ~]# cat /etc/issue*
- \S
- Kernel \r on an \m
- \S
- Kernel \r on an \m
- [root@centos71 ~]# cat /etc/issue
- \S
- Kernel \r on an \m
- [root@centos71 ~]# cat /etc/issue.net
- \S
- Kernel \r on an \m
- [root@centos71 ~]#
- [root@centos71 ~]# diff /etc/issue*
- 3d2
- <
- [root@centos71 ~]# wc /etc/issue.net
- /etc/issue.net
- [root@centos71 ~]# wc /etc/issue
- /etc/issue
(二)登录系统后显示提示信息
- [root@centos61 ~]# ll /etc/motd
- -rw-r--r--. root root Jan /etc/motd
- [root@centos71 ~]# cat /etc/motd
- (@@) ( ) (@) ( ) @@ () @ O @ O @
- ( )
- (@@@@)
- ( )
- (@@@)
- ==== ________ ___________
- _D _| |_______/ \__I_I_____===__|_________|
- |(_)--- | H\________/ | | =|___ ___| _________________
- / | | H | | | | ||_| |_|| _| \_____A
- | | | H |__--------------------| [___] | =| |
- | ________|___H__/__|_____/[][]~\_______| | -| |
- |/ | |-----------I_____I [][] [] D |=======|____|________________________|_
- __/ =| o |=-~~\ /~~\ /~~\ /~~\ ____Y___________|__|__________________________|_
- |/-=|___|=O=====O=====O=====O |_____/~\___/ |_D__D__D_| |_D__D__D_|
- \_/ \__/ \__/ \__/ \__/ \_/ \_/ \_/ \_/ \_/
- [root@centos71 ~]# ll /etc/motd
- -rw-r--r--. root root Dec : /etc/motd
三系统主机名配置文件
文件作用说明:修改主机名称
主机名称: 区域-机房-机柜号码-机器编号 BJ - pbs-010203 - 01
(一)centos6/7系统主机名称临时修改
hostname
- [root@centos61 ~]# hostname
- centos61.huawei.com
- [root@centos61 ~]# hostname centos6.com
- [root@centos61 ~]# exit
- logout
- Connection closed by foreign host.
- Disconnected from remote host(centos6-) at ::.
- Type `help' to learn how to use Xshell prompt.
- [c:\~]$
- Connecting to 10.0.0.61:...
- Connection established.
- To escape to local shell, press Ctrl+Alt+].
- Last login: Thu Dec :: from 10.0.0.1
- [root@centos6 ~]# hostname
- centos6.com
文件内容没有变化
- [root@centos6 ~]# cat /etc/sysconfig/network
- NETWORKING=yes
- HOSTNAME=centos61.huawei.com
- [root@centos7 ~]# hostname centos7.jd.com
- [root@centos7 ~]# exit
- logout
- Connection closed by foreign host.
- Disconnected from remote host(centos7-1) at 09:58:58.
- Type `help' to learn how to use Xshell prompt.
- [c:\~]$ ssh 10.0.0.72
- Connecting to 10.0.0.200:22...
- Connection established.
- To escape to local shell, press Ctrl+Alt+].
- WARNING! The remote SSH server rejected X11 forwarding request.
- Last login: Wed Dec 4 08:27:57 2019 from 10.0.0.1
- [root@centos7 ~]# hostname
- centos7.jd.com
- [root@centos7 ~]# cat /etc/hostname
- centos7.com
(二)centos6系统主机名称永久修改
注意修改之后要重启,注销没用
- [root@centos6 ~]# hostname
- centos6.com
- [root@centos6 ~]# cat /etc/sysconfig/network
- NETWORKING=yes
- HOSTNAME=centos61.com
- [root@centos6 ~]# exit
- logout
- Connection closed by foreign host.
- Disconnected from remote host(centos6-) at ::.
- Type `help' to learn how to use Xshell prompt.
- [c:\~]$
- Connecting to 10.0.0.61:...
- Connection established.
- To escape to local shell, press Ctrl+Alt+].
- Last login: Thu Dec :: from 10.0.0.1
- [root@centos6 ~]# hostname
- centos6.com
重启之后变成了centos61
- [root@centos6 ~]# hostname
- centos6.com
- [root@centos6 ~]# reboot
- Broadcast message from root@centos6.com
- (/dev/pts/) at : ...
- The system is going down for reboot NOW!
- [root@centos6 ~]#
- Connection closed by foreign host.
- Disconnected from remote host(centos6-) at ::.
- Type `help' to learn how to use Xshell prompt.
- [c:\~]$
- Connecting to 10.0.0.61:...
- Connection established.
- To escape to local shell, press Ctrl+Alt+].
- Last login: Thu Dec :: from 10.0.0.1
- [root@centos61 ~]# hostname
- centos61.com
- [root@centos61 ~]# cat /etc/sysconfig/network
- NETWORKING=yes
- HOSTNAME=centos61.com
(三)centos7系统主机名称永久修改
要修改两处
- [root@centos71 ~]# cat /etc/hostname
- centos71.com
- [root@centos71 ~]# sed -i s@@@g /etc/hostname
- [root@centos71 ~]# cat /etc/hostname
- centos7.com
- [root@centos71 ~]# hostnamectl set-hostname centos7.com
- [c:\~]$
- Connecting to 10.0.0.200:...
- Connection established.
- To escape to local shell, press Ctrl+Alt+].
- WARNING! The remote SSH server rejected X11 forwarding request.
- Last login: Thu Dec :: from 10.0.0.1
- [root@centos7 ~]# host
- -bash: host: command not found
- [root@centos7 ~]# hostname
- centos7.com
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