Basic knowledge of Linux three

1. List the user name of all logged-in users on the current system, note: The same user logged in multiple times, only once.

Who | cut-d '-f1 | uniq

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2. Remove the information about the user who last logged in to the current system.

Last | tail-3 |head-1

If a login user name appears, you can use the ID command to see more details.

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3. Remove the shell that is the user's default shell on the current system.

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

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4, the third field in the/etc/passwd the value of the largest 10 users of the information is changed to uppercase and saved to the/tmp/maxusers.txt file.

sort-n-K 3-t ': '/etc/passwd | tail-n | tr [A-z] [a-z] >/tmp/maxusers.txt

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5, take out the IP address of the current host, hint: The result of ifconfig command is sliced.

Ifco nfig | grep ' inet ' | grep-o ' [0-9]\+.* ' | cut-d '-f1 | grep ^1

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

ls/etc | grep ". conf$" | tr ' A-Z ' A-Z ' >/tmp/etc.conf

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7. Displays the total number of sub-directories or files in the/var directory.

ls-l/var | grep "^[d|-]" | wc-l

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8. Remove the names of the 10 groups with the smallest number of the third field in the/etc/group file.

sort-n-T ":"-K 3/etc/group | Head-n 10 | cut-d:-f1

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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

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

(1), create group distro, its GID is 2016;

groupadd-g distro

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

useradd-u 1005-g distro Mandriva

(3), create user Mageia, whose ID number is 1100, home directory is/home/linux;

useradd-u 1100-d/home/linux Mageia

(4), to the user mageia add password, password for mageedu;

echo "magedu" | passwd--stdin Mageia

(5), delete Mandriva, but retain their home directory;

Userdel Mandriva

(6), create user Slackware, its ID number is 2002, the basic group is distro, additional group Peguin;

Groupadd Peguin

Useradd-u 2002-g distro-g Peguin Slackware

(7), modify the Slackware default shell for/BIN/TCSH;

usermod-s/bin/tcsh slackware

(8), add additional Group admins for user Slackware;

groupadd Admins

Usermod-ag Admins Slackware

(9), add password for Slackware, and require the minimum password age of 3 days, the maximum is 180 days, warning for 3 days;

echo "magedu" | passwd--stdin Slackware

usermod-m 3-m 180-w 3 Slackware

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

groupadd clouds groupadd Nova

useradd-u 3003 openstack-g clouds

Usermod-ag Nova,peguin OpenStack

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

useradd-s/sbin/nologin MySQL

(12), use the echo command, non-interactive add a password for OpenStack.

echo "magedu" | passwd--stdin OpenStack

* User-related commands: Useradd, Usermod, Userdel, and more, please use man to help find

* Group-related commands: Groupadd, Groupmod, Groupdel, and more, please use man help to find

This article is from "Bo Zi in the Water" blog, declined to reprint!

Basic knowledge of Linux three