Linux lookup filtering and some examples of user and group management commands _linux

1. List the username of all logged-in users on the current system, and note that the same user logs on more than once, only one display at a time.

~]# who | cut -d' ' -f1 | sort | uniq

2. Lists information about the last user who logged on to the current system.

~]# last | head -1

3. List the most common shell that the user is currently on the system as the default shell.

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

4. Change all the information in the third field in the/etc/passwd to the top 10 users and save 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 address of the current host, hint: ifconfig The result of the command.

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

6. List all the file names in the/etc directory that end with. conf, and convert their 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. Displays the total number of subdirectories or files at the next level in the/var directory.

~]# ls -d /var/* | wc -l

8. Remove the name of the 10 group with the lowest numerical value in the third field in the/etc/group file.

~]# sort -t: -k3 -n /etc/group | cut -d: -f1 | head

9. The contents of the/etc/fstab and/etc/issue files are merged into the same content and saved to the/tmp/etc.test file.

~]# cat /etc/fstab /etc/issue > /tmp/etc.test

10. Summarize the methods used to describe user and group management commands and complete the following exercises:

(1) Create group distro with a GID of 2016

~]# groupadd distro -g 2016

(2) Create user Mandriva, whose ID number is 1005; basic group is distro;

~]# useradd mandriva -u 1005 -g distro

(3) Create user Mageia, its ID number is 1100, home directory is/home/linux;

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

(4) Add the password to the user Mageia, the secret is mageedu;

~]# echo "mageeu" | passwd –stdin mageia

(5) Delete Mandriva, but keep its home directory;

~]# userdel mandriva

(6) Create user Slackware, its ID number is 2002, Basic Group is distro, additional group Peguin;

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

(7) Modify the default shell of Slackware to/BIN/TCSH;

~]# usermod -s /bin/tcsh slackware

(8) Adding additional Group admins for user Slackware;

~]# usermod -a -G admins slackware

(9) Add a password for the Slackware, and require a minimum password of 3 days, up to 180 days, warning for 3 days;

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

(10) Add the user OpenStack, its ID number is 3003, the basic group is clouds, the additional group is Peguin and Nova;

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

(11) Add the system user MySQL, request its shell for/sbin/nologin;

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

(12) Use the Echo command to add a password for OpenStack;

~]# echo openstack | passwd –stdin openstack