Users and user groups under Linux

1, add a test group: Groupadd test

2. Rename the test group Test2:groupmod-n test2 test

3, delete test2 Group: Groupdel test2

4. View the group of the currently logged on user: groups

5, view APAC Group: Groups APAC

6. View all the groups in the system:cat/etc/group a group row with the group name: group Password: gid:[group user, if NULL indicates user group as GID user name]

If there is no/etc/group file, use this command to see: cat/etc/passwd |awk-f [:] ' {print $4} ' |sort|uniq | getent group |awk-f [:] ' {print $ } '

7. View all existing users in the system: Cat/etc/shadow This file is automatically generated by the Pwconv command according to the data in the/etc/passwd

Login: Encrypted password: Last modified: Minimum time interval: Maximum time interval: Warning Time: Inactivity time: Expiry time: Flag

cat/etc/passwd A user row, content is user name: password: uid:gid: User description: Home directory: Login Shell

The password value is x, the password is ciphertext, otherwise the password is plaintext.

Uid:0 is reserved for the root,1~99 system.

Login Shell value/sbin/nologin is not allowed to log on, such as pseudo-user and FTP user.

8, add Users: Useradd–help

Usage:useradd [Options] LOGIN

Options:

-b,–base-dir Base_dir Set the base path as the user's logon directory
-c,–comment comment comments to the user
-d,–home-dir Home_dir Setting the user's login directory
-d,–defaults changing settings
-e,–expiredate Expire_date Set the user's validity period
-f,–inactive inactive user expires, make password invalid
-g,–gid Group enables users to belong to only one group
-g,–groups groups enable users to join a group
-h,–help Help
-k,–skel Skel_dir Specify a different Skel directory
-k,–key key=value Overwrite/etc/login.defs configuration file
-m,–create-home Automatically create login directories
-L, do not add the user to the Lastlog file
-M, do not create the login directory automatically
-R, set up the system account
-o,–non-unique allows the user to have the same UID
-p,–password password using encrypted passwords for new users
-s,–shell Shell Login Time Shell
-u,–uid UID Specifies a UID for the new user
-z,–selinux-user Seuser use a specific seuser for the SELinux user mapping

Note: Useradd add a user, do not forget to give him a password (passwd username), otherwise you cannot log in.

9, delete User: Userdel test

10, modify User: usermod-d/home/test-g test2 Test Change the login directory of the test user to/home/test, and add the Test2 group, note that this is the big G.

11, modify user group: Gpasswd-a username groupname add

gpasswd-d username GroupName Delete

12, view current logged on User: W or who

View current Login user name: WhoAmI

13, view user information: ID username and finger username

14, view login record: Success: last failure: LASTB

15, view all users:cut-d:-F 1/etc/passwd cat/etc/passwd |awk-f \: ' {print $} '

16, modify user password: passwd username

User and user groups under Linux