Linux search and filtering and user and group management command usage

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 | uniq

2. List the information about the users logging on to the current system.

~] # Last | head-1

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

~] # Cut-d:-f7/etc/passwd | 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/maxuser.txt file.

~] # Sort-t:-k3-n/etc/passwd | tail | tr 'A-z'' a-Z'>/tmp/maxuser.txt

5. List the IP addresses of the current host. The prompt is: split the result of the ifconfig command.

~] # Ifconfig | grep '[0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}\. [0-9] \ {1, 3 \}'

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.

~] # Find/etc/-name "*. conf" | tr 'A-z'' a-Z'>/tmp/etc. conf

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

~] # Ls-d/var/* | 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-n/etc/group | cut-d:-f1 | head

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/etc/issue>/tmp/etc. test

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

(1) create a distro group whose GID is 2016

~] # Groupadd distro-g 2016

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

~] # Useradd mandriva-u 1005-g distro

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

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

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

~] # Echo "mageeu" | passwd-stdin mageia

(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;

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

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

~] # Usermod-s/bin/tcsh slackware

(8) add an additional group admins for slackware;

~] # Usermod-a-G admins slackware

(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-n 3-x 180-w 3

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

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

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

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

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

~] # Echo openstack | passwd-stdin openstack