Linux get started common command password-modify password, change user _unix Linux

Source: Internet
Author: User
passwd Command

For system security reasons, each user in a Linux system has a user password in addition to its user name. Therefore, when using the Useradd command, you also need to use the passwd command to set the password for each newly added user, and users can change their passwords at any time with the passwd command.

The general format for this command is: passwd [username] where the user name is the user who needs to modify the password. Only Superuser can use the "passwd username" to modify other user's password, ordinary users can only use passwd command without parameters to modify their password.

The command uses the following methods:

Input

passwd< enter>;

Under (current) UNIX passwd: Enter the password below

At the new password: Prompt to enter the password (not visible on the screen):

The system prompts you to enter this new password again.

After the input is correct, the new password is encrypted and placed in the/etc/shdow file. It is important to choose a password that is not easily deciphered.

Selecting a password should follow the following rules:

The password should have at least six digits (preferably eight-bit) characters;

The password should be a mixture of uppercase and lowercase letters, punctuation marks, and numbers.

The process by which a superuser modifies the password of another user (XXQ) is as follows,

# passwd Root

New UNIX Password:

Retype new UNIX Password:

Passwd:all Authentication Tokens updated successfully

#


SU command

This command is very important. It makes it possible for an average user to have Superuser or other user privileges, or to have a superuser do something as a regular user. A normal user must have the password of a superuser or another user when using this command. If you want to leave the current user's identity, you can play exit.

The general form of the command is: su [options] [?] [User Account]

Note: If you do not specify a user account, the system defaults to Superuser root. The meanings of the options in this command are:

C executes a command and ends.

The purpose of adding this minus sign is to make the environment variable the same as the user you want to convert.

M keeps the environment variable unchanged.
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