限制解锁Linux系统的Limit限制（linux修改limit）

Passwords are a key method of restricting user access to Linux systems. Restrictions are generally established by setting a limit on the number of failed unsuccessful login attempts. Usually, the login attempts that exceeds this limit, the account is then locked and reset. The limit, also known as “Limit”, is specified in the /etc/security/limits.conf file.

When setting up the Limit, administrators typically set a soft limit and a hard limit. The soft limit indicates the maximum number of unsuccessful login attempts that are tried before the account is locked. On the other hand, the hard limit is useful for preventing too many unsuccessful login attempts because it acts as an absolute account lockout.

In order to set up a Limit, the exact syntax should be followed:

For example, to set an account lockout limit of three unsuccessful login attempts and a lockout duration of 15 minutes:

* soft limit 3
* hard limit 3
* reset 15

In this example, if there are more than three unsuccessful login attempts within 15 minutes, the account will be locked and reset. Additionally, if the account is locked out, it will not be usable until the lockout duration is expired.

Once the Limit is set, it can be tested by attempting to log in to the account with an invalid or blank password until the locking limit is reached. Then, the user should wait for the lockout duration to expire before attempting to log in with a valid password. If the account was locked out successfully, then the Limit has been set up correctly.

It is important to note that these Limit settings are global and apply to all users, so administrators should be careful not to enable too restrictive a Limit. Additionally, it is recommended that administrators should use other methods of restricting access, such as two-factor authentication, in order to ensure the security of the system.

In conclusion, setting a Limit is a convenient and powerful way to help keep a Linux system secure by restricting user access. Administrators should consider setting a Limit using the syntax outlined above, in addition to other methods of restricting access, such as two-factor authentication, in order to ensure the system is as secure as possible.