Detailed explanation of Linux system user management and grep regular expressions

本文主要给大家介绍了关于linux系统用户管理与grep正则表达式的相关资料，文中通过示例代码介绍的非常详细，对大家学习或者使用linux系统具有一定的参考学习价值，希望能帮助到大家。

linux系统用户管理与grep正则表达式

1、复制/etc/skel目录为/home/tuser1，要求/home/tuser1及其内部文件的属组和其它用户均没有任何访问权限。

[root@suywien ~]# cp -rpv /etc/skel/ /home/tuser1/
‘/etc/skel/' -> ‘/home/tuser1/'
‘/etc/skel/.mozilla' -> ‘/home/tuser1/.mozilla'
‘/etc/skel/.mozilla/extensions' -> ‘/home/tuser1/.mozilla/extensions'
‘/etc/skel/.mozilla/plugins' -> ‘/home/tuser1/.mozilla/plugins'
‘/etc/skel/.bash_logout' -> ‘/home/tuser1/.bash_logout'
‘/etc/skel/.bash_profile' -> ‘/home/tuser1/.bash_profile'
‘/etc/skel/.bashrc' -> ‘/home/tuser1/.bashrc'
[root@suywien ~]# useradd tuser -d /home/tuser1/
useradd: warning: the home directory already exists.
Not copying any file from skel directory into it.
[root@suywien ~]# chmod -R go-rwx /home/tuser1/
[root@suywien ~]# ll -d /home/tuser1/
drwx------ 3 root root 74 Feb 12 03:04 /home/tuser1/

2、编辑/etc/group文件，添加组hadoop。

[root@suywien ~]# vim /etc/group
[root@suywien ~]# tail -1 /etc/group
hadoop:x:1029

3、手动编辑/etc/passwd文件新增一行，添加用户hadoop，其基本组ID为hadoop组的id号；其家目录为/home/hadoop。

[root@suywien ~]# vim /etc/passwd
[root@suywien ~]# tail -1 /etc/passwd
hadoop:x:1029:1029::/home/hodoop/:/bin/bash

4、复制/etc/skel目录为/home/hadoop，要求修改hadoop目录的属组和其它用户没有任何访问权限。

[root@suywien ~]# cp -fpv /etc/skel/ /home/hadoop
cp: omitting directory ‘/etc/skel/'
[root@suywien ~]# cp -fpvR /etc/skel/ /home/hadoop
‘/etc/skel/' -> ‘/home/hadoop'
‘/etc/skel/.mozilla' -> ‘/home/hadoop/.mozilla'
‘/etc/skel/.mozilla/extensions' -> ‘/home/hadoop/.mozilla/extensions'
‘/etc/skel/.mozilla/plugins' -> ‘/home/hadoop/.mozilla/plugins'
‘/etc/skel/.bash_logout' -> ‘/home/hadoop/.bash_logout'
‘/etc/skel/.bash_profile' -> ‘/home/hadoop/.bash_profile'
‘/etc/skel/.bashrc' -> ‘/home/hadoop/.bashrc'
[root@suywien ~]# chmod go-rwx /home/hadoop/
[root@suywien ~]# ls -ld /home/hadoop/
drwx------ 3 root root 74 Feb 12 03:04 /home/hadoop/

5、修改/home/hadoop目录及其内部所有文件的属主为hadoop，属组为hadoop。

[root@suywien ~]# chown -R hadoop:hadoop /home/hadoop/
[root@suywien ~]# ll -al /home/hadoop/
total 16
drwx------ 3 hadoop hadoop 74 Feb 12 03:04 .
drwxr-xr-x. 10 root root 4096 Mar 25 10:14 ..
-rw-r--r-- 1 hadoop hadoop 18 Nov 20 2015 .bash_logout
-rw-r--r-- 1 hadoop hadoop 193 Nov 20 2015 .bash_profile
-rw-r--r-- 1 hadoop hadoop 231 Nov 20 2015 .bashrc
drwxr-xr-x 4 hadoop hadoop 37 Feb 12 03:03 .mozilla

6、显示/proc/meminfo文件中以大写或小写S开头的行；用两种方式；

[root@suywien ~]# grep ^[S,s] /proc/meminfo 
 SwapCached:   0 kB
 SwapTotal:  2097148 kB
 SwapFree:  2097148 kB
 Shmem:    9100 kB
 Slab:    89476 kB
 SReclaimable:  53176 kB
 SUnreclaim:  36300 kB

[root@suywien ~]# grep -i "^s" /proc/meminfo 
 SwapCached:   0 kB
 SwapTotal:  2097148 kB
 SwapFree:  2097148 kB
 Shmem:    9100 kB

7、显示/etc/passwd文件中其默认shell为非/sbin/nologin的用户；

[root@suywien ~]# grep \/sbin\/nologin$ /etc/passwd
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
......

8、显示/etc/passwd文件中其默认shell为/bin/bash的用户；

[root@suywien ~]# grep \/bin\/bash /etc/passwd
root:x:0:0:root:/root:/bin/bash
roo:x:1000:1000:root:/home/roo:/bin/bash
gentoo:x:4001:4001::/home/gentoo:/bin/bash
mageia:x:1100:1100::/home/linux:/bin/bash
tuser:x:4003:4003::/home/tuser1/:/bin/bash
hadoop:x:1029:1029::/home/hodoop/:/bin/bash

9、找出/etc/passwd文件中的一位数或两位数；

[root@suywien ~]# grep "\<[0-9]\{2,3\}\>" /etc/passwd
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
......

10、显示/boot/grub/grub.conf中以至少一个空白字符开头的行；

[root@suywien ~]# grep "^[[:space:]]\+" /boot/grub2/grub.cfg 
 load_env
 set default="${next_entry}"
 set next_entry=
 save_env next_entry
 set boot_once=true
 ......

11、显示/etc/rc.d/rc.sysinit文件中以#开头，后面跟至少一个空白字符，而后又有至少一个非空白字符的行；

[root@suywien ~]# grep "^#[[:space:]]\+[^[:space:]]\+" /etc/rc.d/rc.local 
# THIS FILE IS ADDED FOR COMPATIBILITY PURPOSES
# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this file.
# In contrast to previous versions due to parallel execution during boot
# this script will NOT be run after all other services.
# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
# that this script will be executed during boot.

12、打出netstat -tan命令执行结果中以‘LISTEN'，后或跟空白字符结尾的行；

[root@suywien ~]# netstat -tan | grep "LISTEN[[:space:]]*$"
tcp  0  0 192.168.122.1:53  0.0.0.0:*    LISTEN  
tcp  0  0 0.0.0.0:22    0.0.0.0:*    LISTEN  
tcp  0  0 127.0.0.1:631   0.0.0.0:*    LISTEN  
tcp  0  0 127.0.0.1:25   0.0.0.0:*    LISTEN  
tcp6  0  0 :::22     :::*     LISTEN  
tcp6  0  0 ::1:631     :::*     LISTEN  
tcp6  0  0 ::1:25     :::*     LISTEN

13、添加用户bash, testbash, basher, nologin (此一个用户的shell为/sbin/nologin)，而后找出当前系统上其用户名和默认shell相同的用户的信息；

[root@suywien ~]# useradd bash
[root@suywien ~]# useradd basher
[root@suywien ~]# useradd -s /sbin/nologin nologin

[root@suywien ~]# grep -E "^([^:]+\>).*\1$" /etc/passwd
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
bash:x:4004:4004::/home/bash:/bin/bash
nologin:x:4006:4006::/home/nologin:/sbin/nologin

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