Common commands for Linux users and management classes

1. List the user name of all the users who have been waiting on the system, note: The same user login more than once, only once can be displayed.
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2 , remove information about the user who last logged on to the current system
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3 , take out the current system on the user as its default shell Most of the shell

4 /etc/passwd The third field in the largest value after 10 Span style= "font-family: ' The song Body '; Each user's information is changed to uppercase and saved to /tmp/maxusers.txt

5 , remove the current host's Ip address, tip: Slice the ifconfig command.
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6 , take out /etc/ directory all under . Com 650) this.width=650; "height=" 640 "src=" http://b200.photo.store.qq.com/psb?/V14ApF1036yr41/ einmm2fcmhhjqjcqfn59j9dxxph9luotyym0ymx0ds4!/b/dmgaaaaaaaaa&bo=6wkaagaaaaafaeg! "width=" 747 "style=" vertical-align:top; "alt=" dmgaaaaaaaaa&bo=6wkaagaaaaafaeg! "/> 

7 , display /var 650) this.width=650, "height=", "src=" http://b200.photo.store.qq.com/psb?/v14apf1036yr41/ewvh5ojld* Qwhi3sish7lsxwyy.tr83j34ghzsnxwlm!/b/dmgaaaaaaaaa&bo=gge7aaaaaaafajs! "width=" 386 "style=" vertical-align:top ; "alt=" dmgaaaaaaaaa&bo=gge7aaaaaaafajs! "/> 

8 , take out /etc/group The third field in the file has the lowest value 10 Span style= "font-family: ' The song Body '; > The name of the group.
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9 /etc/fstab and /etc/issue  650) this.width=650; "height=" 289 "src=" http://b264.photo.store.qq.com/psb?/V14ApF1036yr41/ ix5ezdf8ygllnolque9rtq9wslfgxzn7flj9vedtgv0!/b/dagbaaaaaaaa&bo=2aihaqaaaaafank! "width=" 728 "style=" vertical-align:top; "alt=" dagbaaaaaaaa&bo=2aihaqaaaaafank! "/>

10     (1), create group distro, its GID is 2016; 
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(2), create user Mandriva, whose ID number is 1005; basic group is distro;
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(3), create user Mageia, whose ID number is 1100, home directory is/home/linux;
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(4), to the user mageia add password, password for mageedu;
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(5), delete Mandriva, but retain their home directory;
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< Span style= "font-family: ' The song Body '; >    (6), create user Slackware, its ID number is 2002, Basic Group is distro, additional group Peguin;
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< Span style= "font-family: ' The song Body '; >    (7), modify Slackware default shell is/bin/tcsh; 
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(8), add additional Group admins for user Slackware;
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(9), add password for Slackware, and require the minimum password age of 3 days, the maximum is 180 days, warning for 3 days;
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< Span style= "font-family: ' The song Body '; >    (10), add user OpenStack, whose ID number is 3003, base Group is clouds, additional group is Peguin and Nova;
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(11), add the system user MySQL, request its shell for/sbin/nologin;
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(12), use the echo command, non-interactive add a password for OpenStack.
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There are 4 groups of Linux users associated with the configuration file:

/ETC/PASSWD: Saving users and their property information

Meaning of each field

Root:x:0:0:root:/root:/bin/bash

User name: Password dot: uid:gid: Comment Information: Home directory: User default Shell

/etc/group: Group and its attribute information

The meaning of each field:

Root:x:0:root

Group name: group password dot: GID: comma-delimited list of users belonging to this group

/etc/shadow: User passwords and their associated properties

The meaning of each field:

Root:$1$mq0q9ij0$mjtq5cavkibpd5pvbflnp0:16521:0:99999:7:::

Username: encrypted Password: the date of the most recent password change: Minimum password Age: Maximum password Age: Password Disable period: Account expiration Date: Reserved field

/etc/gshadow: group password and its related properties

User and group-related administrative commands:

Useradd: Create User

-U: Specify UID

-G: Specify GID

-C: User's comment information

-D: Specify the user's home directory

-S: Specify the user's default shell program

-G: Specify additional groups for users

-r: Create a System user

Groupadd: Creating Groups

-G: Indicates GID

-R: Creating a System Group

Usermod: User Property modification

-U: New UID

-G: New GID

-G: The new Add-on group, the original additional group will be overwritten, if the original, you want to use the-a option, indicating append

-S: New default shell

-C: New annotation information

-D: New home directory, files in the original home directory are not moved to the new home directory at the same time, to move, use the-M option

-L: New name

-L: Lock the specified user

-U: Unlock the specified user

passwd: Change Password

--stdin: Don't change passwords interactively

Userdel: Deleting users

-r: Delete User home directory

Groupmod: Group Property Modification

-N: New group name

-G: New GID

Groupdel: Group Delete

GPASSWD: Group Password

-A User: Add user to the specified group

-D User: Removes additional groups of users with the current group as the group name

-A User1,user2,... : Set up a list of users with administrative rights

Common commands for Linux users and management classes