Linux text processing commands, user and group command exercises

1. List the usernames of all logged-on users on the current system. Only one user logon is displayed.

[Root @ localhost ~] # Who
Root tty1
Root pts/0 2016-08-26 05:09 (172.16.16.201)
User1 pts/1 2016-08-26 05:11 (172.16.16.201)
[Root @ localhost ~] # Who | cut-d ''-f1 | uniq root
User1

2. Retrieve the information about the user logging on to the current system.

[User1 @ localhost ~] $ Last | head-1
User1 pts/1 172.16.16.201 Fri Aug 26 05:36 still logged in

3. Retrieve the shell on the current system that the user uses as the largest default shell.

# Sort and count the 7th fields in/etc/passwd
 
[Root @ localhost ~] # Cut-d:-f7/etc/passwd | sort | uniq-c
2/bin/bash
4/bin/sh
1/bin/sync
1/sbin/halt
15/sbin/nologin
1/sbin/shutdown
      
# Sort by value
 
[Root @ localhost ~] # Cut-d:-f7/etc/passwd | sort | uniq-c | sort-n
1/bin/sync
1/sbin/halt
1/sbin/shutdown
2/bin/bash
4/bin/sh
15/sbin/nologin
      
# Obtain the shell of the last row
# Final result
 
[Root @ localhost ~] # Cut-d:-f7/etc/passwd | sort | uniq-c | sort-n | tail-1 | grep-o [^ [: space:] * $
/Sbin/nologin
4. Change the information of the last 10 users with the maximum value of the Third Field in/etc/passwd to uppercase and save the information to the/tmp/maxusers.txt file.

# Sort the fields in the/etc/passwd file by colons (:) and sort the values of the 3rd Fields. The last 10 rows are obtained.
 
[Root @ localhost ~] # Sort-n-t:-k3/etc/passwd | tail
Vcsa: x: 69: 69: virtual console memory owner:/dev:/sbin/nologin
Sshd: x: 74: 74: Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
Postfix: x: 89: 89:/var/spool/postfix:/sbin/nologin
Nobody: x: 99: 99: Nobody: // sbin/nologin
Saslauth: x: 499: 76: Saslauthd user:/var/empty/saslauth:/sbin/nologin
User1: x: 500: 500:/home/user1:/bin/bash
Gentoo: x: 4001: 4001:/home/gentoo:/bin/sh
Fedora: x: 4002: 4002: Fedora Core:/home/fedora:/bin/sh
User2: x: 4003: 4003:/home/user2:/bin/sh
User3: x: 4004: 4004:/home/user3:/bin/sh
 
# Send the above results to the command "tr" in an upper-case mode through the pipeline and redirect to/tmp/users.txt.
# Final result
 
[Root @ localhost ~] # Sort-n-t:-k3/etc/passwd | tail | tr 'A-z'' a-Z'>/tmp/maxusers.txt

5. Split the command ifconfig result to retrieve the IP address of the current host.

# Retrieve the addr address in the command "ifconfig" result
 
[Root @ localhost ~] # Ifconfig | grep-E-o "addr: [0-9] {1, 3 }\. [0-9] {1, 3 }\. [0-9] {1, 3 }\. [0-9] {1, 3 }"
Addr: 172.16.16.1
Addr: 127.0.0.1
 
# Pipeline sends the command "cut" to retrieve the address
# Final result
 
[Root @ localhost ~] # Ifconfig | grep-E-o "addr: [0-9] {1, 3 }\. [0-9] {1, 3 }\. [0-9] {1, 3 }\. [0-9] {1, 3} "| cut-d:-f2
172.16.16.1127.0.0.1

6. List all file names ending with. conf in the/etc directory, convert the names to uppercase, and save them to/tmp/etc. conf.
1
[Root @ localhost ~] # Ls/etc/*. conf | tr 'A-z'' a-Z'>/tmp/etc. conf

7. Display the total number of first-level subdirectories or files under the/var Directory

[Root @ localhost ~] # Ls/var | wc-l19

8. Retrieve the names of the 10 groups with the minimum value of the 3rd fields in the/etc/group file.

# 3rd the fields are sorted by numerical values, and the first 10 rows are obtained.
 
[Root @ localhost ~] # Sort-t:-k3-n/etc/group | head
Root: x: 0:
Bin: x: 1: bin, daemon
Daemon: x: 2: bin, daemon
Sys: x: 3: bin, adm
Adm: x: 4: adm, daemon
Tty: x: 5:
Disk: x: 6:
Lp: x: 7: daemon
Mem: x: 8:
Kmem: x: 9:
 
# Send it to "cut" via MPs queue and get the group name
# Final result
 
[Root @ localhost ~] # Sort-t:-k3-n/etc/group | head | cut-d:-f1
Root
Bin
Daemon
Sys
Adm
Tty
Disk
Lp
Mem
Kmem

9. Merge the/etc/fstab and/etc/issue files into the same content and save it to the/tmp/etc. test file.

[Root @ localhost ~] # Cat/etc/fstab>/tmp/etc. test
[Root @ localhost ~] # Cat/etc/issue>/tmp/etc. test
10. User and group management command exercises

10.1 create a distro group whose GID is 2016

[Root @ localhost ~] # Tail/etc/group
[Root @ localhost ~] # Tail-1/etc/group
Distro: x: 2016:

10.2 Create a user named mandriva with the ID number 1005 and the BASIC group named distro.

[Root @ localhost ~] # Useradd-u 1005-g distro mandriva
[Root @ localhost ~] # Id mandriva
Uid = 1005 (mandriva) gid = 2016 (distro) groups = 2016 (distro)
10.3 create mageia user. The ID number is 1100, and the home directory is/home/linux

[Root @ localhost ~] # Useradd-u 1100-d/home/linux mageia
[Root @ localhost ~] # Tail-1/etc/passwd
Mageia: x: 1100: 1100:/home/linux:/bin/sh

10.4 add a password for mageia to the user. The password is mageedu.

[Root @ localhost ~] # Echo "mageedu" | passwd -- stdin mageia
Changing password for user mageia.
Passwd: all authentication tokens updated successfully.

10.5 delete mandriva but keep its home directory

You can directly delete the user's mandriva, because the default home directory is retained.

[Root @ localhost ~] # Userdel mandriva
[Root @ localhost ~] # Ls/home
Fedora gentoo linux lost + found mandriva user1 user2 user3

10.6 create the slackware user. The ID number is 2002, the BASIC group is distro, and the additional group is peguin.

[Root @ localhost ~] # Useradd-u 2002-g distro-G peguin slackware
[Root @ localhost ~] # Id slackware
Uid = 2002 (slackware) gid = 2016 (distro) groups = 2016 (distro), 5001 (peguin)

10.7 modify slackware's default shell to/bin/tcsh

[Root @ localhost ~] # Usermod-s/bin/tcsh slackware
[Root @ localhost ~] # Grep ^ slackware/etc/passwd
Slackware: x: 2002: 2016:/home/slackware:/bin/tcsh

10.8 add an additional group admins for slackware

[Root @ localhost ~] # Groupadd admins
[Root @ localhost ~] # Usermod-a-G admins slackware
[Root @ localhost ~] # Id slackware
Uid = 2002 (slackware) gid = 2016 (distro) groups = 2016 (distro), 5001 (peguin), 5003 (admins)

10.9 add a password for slackware. The minimum password validity period is 3 days, the maximum password is 180 days, and the warning is 3 days.

[Root @ localhost ~] # Echo "slackware" | passwd -- stdin slackware
Changing password for user slackware.
Passwd: all authentication tokens updated successfully.
[Root @ localhost ~] # Grep ^ slackware/etc/shadow | cut-d:-f4-6
3: 180: 3

10.10 add an openstack user. The ID number is 3003, the BASIC group is clouds, and the additional groups are peguin and nova.

[Root @ localhost ~] # Useradd-u 3003-g clouds-G peguin openstack
[Root @ localhost ~] # Usermod-a-G nova openstack
[Root @ localhost ~] # Id openstack
Uid = 3003 (openstack) gid = 5004 (clouds) groups = 5004 (clouds), 5001 (peguin), 5005 (nova)
10.11 add the system user mysql and require the shell to be/sbin/nologin.

[Root @ localhost ~] # Useradd-r-s/sbin/nologin mysql
[Root @ localhost ~] # Tail-1/etc/passwd
Mysql: x: 498: 498:/home/mysql:/sbin/nologin

10.12 use the echo command to add a password for openstack in non-interactive mode

[Root @ localhost ~] # Echo "openstack" | passwd -- stdin openstack
Changing password for user openstack.
Passwd: all authentication tokens updated successfully.