Basic knowledge of user ﹑ password ﹑ file access rights and security in Linux

User home directory ﹑ Super User and add other user

For a typical user, there may be only its own home directory where a write can be performed on a hard disk, which is under "/home/username."

The/home directory saves all user files, including user settings, program profiles, documents, data, Netscape cache files, and user mail. Ordinary users can simply create a new subdirectory under their home directory to organize your files. And without giving other users normal user rights, other users are not authorized to read or write content in your home directory.

In addition to their home directory, the average user can find ﹑ read ﹑ execute files in other directories within the system, but generally they cannot modify or move the files.

A superuser (also known as "root") is a special account that has the power to modify any file in the system. In daily work, it is best not to use the Super user account to enter the system, because any error operation can cause huge losses. Since the Superuser account is the only account that is available after the system is established, you need to establish and use a general user account for daily work.

Super User root can create a new user account, for example, the following command creates a new user named Joe. # AddUser Joe

# passwd Joe (type Joe's password)

Root can modify the password of any user without knowing the user's current password (the password is encrypted with a one-way encryption algorithm, and the encrypted result is saved in the file/etc/passwd, and the original password is not saved). When you register, the password you type is also computed by a one-way encryption algorithm, and the result is compared to the value saved in/etc/passwd.

Linux uses a strategy that separates administrators from ordinary users, which ensures robustness of the system and makes it difficult to write a virus under Linux (a user writes a program that only has write access to its own directory and is separated from other parts of the operating system).

In general, users need to modify their passwords immediately when they first register. The order is as follows: $ passwd

(current) Unix Password [type old password Word]

New Unix Password [type password Word]

Retype new UNIX password [again type the password Word]

For security reasons, the password you type is not displayed back on the screen.

Security of passwords

Weak passwords are the main cause of system insecurity, and here are examples of unsafe passwords.

1. The word "password" as a password;

2. Take the name of yourself or someone else as your password;

3. Take the company name, department name or group name as the password;

4. Take birthday as a password;

5. Write the password on the calendar or next to the computer;

6. Use words or common words in a dictionary;

A good password should be at least 6 letters long, containing letters and numbers, and should be modified frequently.

The system administrator can configure a program to set the security policy for the password. For example, you can start the linuxconf utility as root:

# linuxconf

Configure the password under menu user Accountêpoliciesêpassword & Account policies.