Linux user, group, and password management

This article mainly summarizes common commands and options for Linux users and group management.

I. User Management

1. Add a user

Command: useradd

-U	UID, valid range: 0-65536
-G	GID, which must already exist
-G	GID, additional group, must exist
-C	Note
-D	User directory
-S	Specify User shell
-R	System User UID creation is between 1 and), the System user does not automatically create a home directory
-M	You must create a home directory for the user.
-M	Do not create home directories for users

Passwd USERNAME: Set the password for the user

Passwd-l USERNAME: User locked

Passwd-u USERNAME to unlock a user

2. view User attributes

Command 1: id

-U	Show UID only
-G	Show only basic GID
-G	Show all gids
-N	It is displayed as data and used together with u, g, and other options

Command 2: finger this command tool needs to be installed separately)

3. Modify user attributes

Command: usermod

-U	Modify UID
-G	Modify GID
-A-G	Modify the extra group. Option-a can retain the original extra group.
-C	Modify comments
-S	Modify User shell
-L	Modify user name
-M-d	Modify the home directory. The-m option can be used to move the original home directory to a new home directory.

2. Group Management

1. Add a user group

Command: groupadd

-G	Specify GID
-N	Create System Group

Set the password for the gpasswd GROUPNAME group.

Newgrp GROUPNAME: temporarily switch the specified group to the basic group. The password has been set)

2. Modify group attributes

Command: groupmod

-G	Modify GID
-N	Modify group name

Iii. Password Management

Command 1: passwd

-E	The password expires and requires the user to change the password upon next login
-N	Minimum Password usage days
-X	Maximum days
-W	Warning days
-I	Inactive duration

Command 2: chage

-D	Last password modification time
-M, -- mindays MIN_DAYS	Shortest term
-M, -- maxdays MAX_DAYS	Maximum service life
-W, -- warndays WARN_DAYS	Warning days
-I, -- inactive INACTIVE	Inactive days
-E, -- expiredate EXPIRE_DATE	Expiration time

Command 3: usermod

-E YYYY-MM-DD

Expiration time of the specified account

This article from the "Linux/Unix O & M Technology" blog, please be sure to keep this source http://wangyc.blog.51cto.com/31193/1304826