Users and Groups for Linux

First, user and group of related files

/etc/passwd  :  user and its attribute information file format:    root:x:0:0:root:/root:/bin/bash      Username: Password: uid:gid: Description Information: Home directory: Default shell #============================================================ ==========================       /etc/shadow  :  User password store information file format:    root:xxxxx:17485:0:99999:7:::     user name: encrypted password: Password modification time: Minimum validity: Maximum period: Advance reminder number of days to change password: expired n days after the login: account validity #====================================================================== ================     /etc/group   :  Group and its attribute information file format:     root:x:0:     Group name: Group password: Group ID: team member #================================================== ====================================          /etc/gshadow  :  group Password and its attribute information file format:    root:x:x:     Group name: password: Group Administrator: Team member      #====================================================================================== 

Second, the user management of the relevant orders

1. User add: Useradd

Usage:useradd [options] login    -u uid:  Specify UID    -G  GID:  Specify a basic group, you can use the group name to specify     -d HOME_DIR:  specify the home (nonexistent) directory      -s SHELL:  specify default shell    -g group1[,group2,...]: To specify additional groups for the user, the group must exist      -r :  Create System User (default does not create home directory)     -m :  Force home Directory, with-R use      -N :  do not create basic groups with the same name, use the Users group to do basic groups     -M :  do not create home directories      -o :  with-u use, do not check UID uniqueness     -c :  Add description information newusers  file :  batch create user, need to be prepared with passwd format file chpasswd :  Bulk Modify user password, file format: User name: Password      Example: cat password.txt | chpasswd    /etc/default/useradd :  Create a user's default file     useradd -d: Show default values     useradd -D -s  shell  :  Modifying the default SHELL    USERADD -D -B BASE_DIR &NBSP: Modify default home directory      Useradd -d -g group: Modify the default group/etc/login.defs  :  detailed create user profile/etc/skel/ :  User home directory of the. BASHRC ... Documents, etc. #======================================================================================

2. Modify User password: passwd

Usage: passwd [options] UserName passwd: Modify your own password options:-L: Lock specified user-u: Unlock specified user-e: Force user to change password at next logon--stdin: Receive from standard input User Password Example: echo "PASSWORD" | passwd--stdin USERNAME #======================================================================================

3. Modify user information: Usermod

Usage: usermod [options] login-g GID: Modify user base Group-G GID,GID1: Modify user Additional group-a: With-G use, add additional group-L New_name: Modify user logon Name-     L: Lock the user, will be added in the/etc/shadow password bar! -U: Unlock user-E yyyy-mm-dd: Specify user account expiration date-D DIR: Modify home Directory-M: with-D, modify and move data to the new home directory #================================== ====================================================

4. Delete User: Userdel

Usage: Userdel [options] login-r: Delete home directory-F: Force Delete #==================================================================== ==================

5. View user-related ID information

ID: Show User ID number usage: id [OPTION] ... [User]-U: Display uid-g: Display gid-g: Displays the id-n of the group to which the user belongs: Display name, with-G use #=============================================== =======================================

Iii. related commands for group management

1. Create and delete groups: Groupadd, Grupdel

Create group: Usage: groupadd [options] Group option:-G GID: Specify GID-R: Create System Group Delete Group: Groupdel Group #============================== ========================================================

2. Modify Group Properties: Groupmod

Usage: groupmod [options] Group options:-N group_name: Modify group name-G GID: Modify gid#================================================= =====================================

3. Change group Password: gpassed

Usage: gpassed [options] Group options:-A User: Add users to Group-D User: Remove user from group-a user1,user2 ...: Set group Administrator #=========== ===========================================================================

4. Change Group members: Groupmems

Usage: groupmems [options] [action] option:-G,--group groupname: Change to specified group-a,--add Username: Add user to Group-d,--Delete Usern Ame: Remove users from Group-P,--purge: Clears all members of the group-l,--list: Displays the group member list #================================================== ====================================

This article is from the "Bigboss" blog, make sure to keep this source http://bigboss.blog.51cto.com/12113895/1982128

Users and Groups for Linux