An in-depth analysis of the functions and working principles of the Linux chage command

The chage command in the Linux system is a command used to modify the password expiration date of a user account. It can also be used to modify the longest and shortest usable date of the account. This command plays a very important role in managing user account security. It can effectively control the usage period of user passwords and enhance system security.

How to use the chage command:

The basic syntax of the chage command is:

chage [选项] 用户名

For example, to modify the password expiration date of user "testuser", you can use the following command:

chage -l testuser

chage command options:

• -E DATE: Set the password expiration date.
• -M DAYS: Set the maximum number of days for password use.
• -m DAYS: Set the minimum number of days for password use.
• -I DAYS: The number of warning days before the password expires.
• -W DAYS: The number of warning days before the account is locked after the password expires.

Principle of the chage command: The

chage command is actually implemented by modifying the /etc/shadow file of the user account. In Linux systems, user passwords are stored in encrypted form in the /etc/shadow file, and the chage command changes the values ​​of relevant fields in the /etc/shadow file, thereby modifying attributes such as the password expiration date.

The following uses a specific example to illustrate the use and principle of the chage command:

Assume that the password expiration date of user "testuser" is to be modified on December 31, 2022, and the maximum number of days of use is 90 days, the minimum number of days is 7 days, the number of warning days before the password expires is 14 days, the number of warning days before the account is locked after the password expires is 7 days, you can follow the steps below:

1. View The current account information of "testuser":

chage -l testuser

2. Modify the relevant attributes of the account:

chage -E 2022-12-31 -M 90 -m 7 -I 14 -W 7 testuser

3. Check the account information of "testuser" again to confirm the modification Effective:

chage -l testuser

Through the above operations, you can successfully modify the password expiration date and other related attributes of user "testuser".

In general, the chage command is a very practical command that can help administrators flexibly manage the security of user accounts and strengthen system security by controlling attributes such as password expiration dates.

The above is the detailed content of An in-depth analysis of the functions and working principles of the Linux chage command. For more information, please follow other related articles on the PHP Chinese website!