Linux notes Linux user, group management

1. Linux User, group management

1) user

I. Adding users

Useradd User Name

Useradd add users directly without parameters, home directory defaults to the bash shell

Example 1:

[Email protected] etc]# Useradd Testyx

[Email protected] etc]# Cd/home

[[email protected] home]# ls

Ads_yx Testyx

[Email protected] home]# passwd Testyx

Changing password for user Testyx.

New Password:

Bad Password:it is too simplistic/systematic

Bad Password:is too simple

Retype new Password:

Passwd:all authentication tokens updated successfully.

[Email protected] home]# Cat/etc/passwd|grep Testyx

Testyx:x:501:502::/home/testyx:/bin/bash

Useradd-d Home Directory-G Group name-group collection (comma interval)-p password-S shell user name

Example 2:

[Email protected] home]# useradd-d/home/test1-g test-p 123456-s/bin/bash testyx1

[Email protected] home]# Cat/etc/passwd|grep testyx1

Testyx1:x:502:501::/home/test1:/bin/bash

[Email protected] home]# Cat/etc/group|grep test

test:x:501:

testyx:x:502:

Ii. Modifying users

Usermod

-c< Notes > Modify the Notes text for the user account.
-D Login Directory > Modify user login directory.
-e< Expiration date > Modify the expiration date of the account.
-f< Buffer days > Modify the number of days after the password expires to close the account.
-g< Group > Modify the group to which the user belongs.
-g< Group > Modify the additional groups to which the user belongs.
-l< Account name > Modify user account name.
-L LOCKS the user password to invalidate the password.
-s<shell> modifies the shell used by the user when they log in.
-u<uid> Modify the User ID.
-U unlocks the password.

Note: When changing home directories, the destination home directory must exist and be an absolute path

Example 1: Modify the Testyx user name to Testyxc
# usermod-l Testyxc Testyx
Example 2: Lock account Testyxc
# usermod-l TESTYXC
Example 3: Unlocking the TESTYXC
# usermod-u TESTYXC

Iii. Deleting a user

Userdel User Name

Delete User only, do not delete home directory

Cases:

[Email protected] home]# Userdel Testyx

[Email protected] home]# Cd/home

[email protected] home]# LL

Total 12

DRWX------3 Ads_yx yxtest 4096 Sep 07:52 Ads_yx

DRWX------2 testyx1 test 4096 Sep 01:57 test1

DRWX------2 501 502 4096 Sep 01:50 Testyx

Userdel-r User Name

Delete User and home directory

Cases:

[Email protected] home]# Userdel-r testyx1

[email protected] home]# LL

Total 8

DRWX------3 Ads_yx yxtest 4096 Sep 07:52 Ads_yx

DRWX------2 501 502 4096 Sep 01:50 Testyx

You can see that the testyx1 user home directory test1 has been deleted

2) Switch User

i. su user name

Switch user's environment variables are not reloaded

Cases:

[Email protected] home]# cd/opt

[Email protected] opt]# pwd

/opt

[email protected] opt]# su Ads_yx

[Email protected] opt]$ pwd

/opt

You can see that the current directory has not changed after switching to the Ads_yx user

II. su– User name

The environment variable that will reload the switch user

[Email protected] opt]# pwd

/opt

[Email protected] opt]# Su-ads_yx

[Email protected] ~]$ pwd

/home/ads_yx

You can see that the current directory changes to Ads_yx's home directory after switching to the Ads_yx user, because the user's environment variable was reloaded when Su–ads_yx

III. sudo

Get Superuser privileges under normal user

configuration: Locate root all= (all) in the/etc/sudoers file and add and save the following:

Ads_yx all= (All) Nopasswd:all

　　　　　　

3) view Current user

I. Viewing the UID and GID of the current user

[[email protected] home]# ID

Uid=0 (Root) gid=0 (root) groups=0 (root)

II. See who the current user is

[Email protected] home]# WhoAmI

Root

4) environment Variables

i. system Environment Variables

The system environment variable is placed in the/etc/profile file, making the environment variable effective as the source command

　　　　　　

[Email protected] ~]# echo $PATH

/opt/lampp/bin:/opt/jdk1.7.0_75/bin:/opt/jdk1.7.0_75/jre/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/ Sbin:/usr/bin:/root/bin

II. User Environment variables

The user's own environment variable is placed in the. bash_profile file in the user's home directory * (the shell for this example is bash)

　　　　　　

[Email protected] ~]# Su-ads_yx

[Email protected] ~]$ echo $PATH

/opt/lampp/bin:/opt/jdk1.7.0_75/bin:/opt/jdk1.7.0_75/jre/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr /sbin:/sbin:/home/ads_yx/bin

iii. env viewing environment variables

[[Email protected] ~]$ env

Shell=/bin/bash

Term=xterm

histsize=1000

Jre_home=/opt/jdk1.7.0_75/jre

User=ads_yx

......

Path=/opt/lampp/bin:/opt/jdk1.7.0_75/bin:/opt/jdk1.7.0_75/jre/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin :/usr/sbin:/sbin:/home/ads_yx/bin

......

5) user Group

Iv. Adding a user group

GROUPADD-G Group ID Group name

Cases:

[Email protected] ~]# groupadd-g 580 TESTCC

[Email protected] ~]# Cat/etc/group|grep TESTCC

testcc:x:580:

V. Modifying a user group

Groupmod-g New Group Id–n group new name group old name

Cases:

[Email protected] ~]# groupmod-g 581 TESTCC

[Email protected] ~]# Cat/etc/group|grep TESTCC

testcc:x:581:

Vi. Deleting a user group

Groupdel Group Name

Cases:

[Email protected] ~]# Groupdel TESTCC

[Email protected] ~]# Cat/etc/group|grep TESTCC

[[Email protected] ~]#--Query not to group information

Linux notes Linux user, group management