Common commands for Linux user and group management

1. List the usernames of all logged-on users on the current system. Note: Only one user can be logged on multiple times.

~] # Who | cut-d ""-f1 | sort-u

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

~] # Last-x | head-1

3. Retrieve the shell on the current system that is most used as the default shell.

~] # Cut/etc/passwd-d ":"-f7 | uniq-c sort-n tail-1

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-t ":"-k3-n/etc/passwd | tail-10 tr [[: lower:] [[: upper:]>/tmp/maxuser.txt

5. Retrieve the IP address of the current host. The prompt is: split the result of the ifconfig command.

~] # Ifconfig | grep 'inet '| grep-v '2017. 0.0.1' | cut-d:-f2 | awk '{print $2 }'

6. List all file names ending with. conf in the/etc directory, convert the names to uppercase, and save them to the/tmp/etc. conf file.

~] # Ls-a/etc | egrep *. conf $ | tr [[: lower:] [[: upper:]>/tmp/etc. conf

7. Display the total number of subdirectories or files under the/var directory.

~] # Find/var-type f wc-l

8. Retrieve the names of the 10 groups with the minimum value of the third field in the/etc/group file.

~] # Sort-t ":"-k3/etc/group | head-10 | cut-d ":"-f1

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

~] # Cat/etc/{fstab, issue}> tmp/etc. test

10. Summarize the usage of user and group management commands and complete the following exercises:

(1) create a distro group with a GID of 2016;

~] # Groupadd distro-g 2016

~] # Cat/etc/group | grep distro

(2) create a user named "mandriva", whose ID number is 1005, and the BASIC group is "distro;

~] # Useradd-u 1005-g 2016 mandriva

~] # Cat/etc/passwd | grep mandriva

Mandriva: x: 1100: 2016:/home/mandriva:/bin/bash

(3) create the mageia user. The ID number is 1100, and the home directory is/home/linux;

~] # Useradd-u 1100-d/home/linux mageia

~ [Root @ localhost tmp] # cat/etc/passwd | grep mageia

Mageia: x: 1100: 1100:/home/linux:/bin/bas

(4) add a password for mageia to the user. The password is mageedu;

~] # Passwd mageia

Changing password for user mageia.

New password:

Bad password: The password is shorter than 8 characters

Retype new password:

Passwd: all authentication tokens updated successfully.

(5) delete mandriva, but keep its home directory;

~] # Userdel mandriva

(6) create the slackware user. The ID number is 2002, the BASIC group is distro, and the additional group is peguin;

~] # Groupadd peguin

~] # Useradd-u 2002-g distro-G peguin slackware

~] # Cat/etc/passwd | grep slackware

Slackware: x: 2002: 2016:/home/slackware:/bin/bash

~] # Id slackware

Uid = 2002 (slackware) gid = 2016 (distro) group = 2016 (distro), 2017 (peguin)

(7) modify slackware's default shell to/bin/tcsh;

~] # Usermod-s/bin/tcsh slackware

~] # Cat/etc/passwd | grep slackware

Slackware: x: 2002: 2016:/home/slackware:/bin/tcsh

(8) add an additional group admins for slackware;

~] # Usermod-aG admins slackware

~] # Id slackware

Uid = 2002 (slackware) gid = 2016 (distro) group = 2016 (distro), 2017 (peguin), 2018 (admins)

(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;

~] # Passwd slackware

Changing password for user slackware.

New password:

Bad password: The password fails the dictionary check-it is too simplistic/systematic

Retype new password:

Passwd: all authentication tokens updated successfully.

~] # Passwd-n 3-x 180-w 3 slackware

Adjusting aging data for user slackware.

Passwd: Success

~] # Cat/etc/shadow | grep slackware

Slackware: $6 $ gk2px/TP

$ Response.: 17056: 3: 180: 3 :::

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

~] # Groupadd clouds

~] # Groupadd nova

~] # Useradd-u 3003-g clouds-G peguin, nova openstack

~] # Id openstack

Uid = 3003 (openstack) gid = 2019 (clouds) group = 2019 (clouds), 2017 (peguin), 2020 (nova)

(11) add the system user mysql and require the shell to be/sbin/nologin;

~] # Useradd-r-s/sbin/nologin mysql

~] # Cat/etc/passwd | grep mysql

Mysql: x: 988: 983:/home/mysql:/sbin/nologin

(12) use the echo command to add a password for openstack in non-interactive mode.

~] # Echo "12345678" | passwd-stdin openstack

Changing password for user openstack.

Passwd: all authentication tokens updated successfully.