Management of groups and users in Linux

The instructions for setting up a group in Linux are

Groupadd Group Name

Corresponding, delete the group of instructions:

Groupdel Group Name

To view the groups of your own users:

Groups

User management:

USERADD-S/BIN/BASH-G Group name User name

-S indicates that the user opened the terminal after landing, here is/bin/bash, if you want to disable logging, can be set to/sbin/nologin

-M does not establish the user's home folder, user login will run to/go. Can be created manually, if it is forbidden to login, it is recommended to add this parameter

Since there are useradd instructions, of course, there are corresponding Userdel ...

Users are used to see who is currently logged in. Only the user name is not detailed

You can use W or the WHO directive to view details, W information is more complete, including:

User name Terminal IP login time how long has not moved the operation consumes CPU time program consumes CPU time (the meaning of this two CPU time I am not sure, here may be wrong) in the running program (usually the only one running W is itself ~)

Terminal is a type of character device, it has many types, usually use TTY to short for various types of terminal equipment

--------------------------the following references from http://7056824.blog.51cto.com/69854/276610----------------------------

TTY: Commonly used serial cable connection, keyboard and mouse direct connection, and other ways to connect, called terminal

Pty: Virtual terminal, we will allocate virtual terminal when we connect remotely through the network.

PTS: is an implementation of Pty, implemented Pty with PTMX (Pseudo-terminal master).

--------------------------above are quoted from http://7056824.blog.51cto.com/69854/276610----------------------------

So many users, do not know which is their own?

Use Who am I to see which is my own

Use this instruction T to drop the user (requires permission):

PKILL-KILL-T Terminal

You can send a message to the specified user:

You may need to use the MESG y command to allow messages to be received, or others cannot actively connect

You can use MESG N to close

Input MESG card Current settings

Write User name Terminal

Enter the message input mode, enter the message return opposite to receive, CTRL + C exit.

You can also broadcast globally:

Wall + Message

You can do it as usual when you receive the message!

The terminal can be seen under dev, such as viewing pts:

ls/dev/pts/

echo Text to the PTS file, which will be displayed opposite.

But the appropriate permissions are required

Management of groups and users in Linux