Knowledge about user information and passwords in Linux

In Linux, if you modify the user information, password, group information, password, etc., in fact, in the modification of the contents of the /etc/passwd,/etc/shadow,/etc/group,/etc/groupshadow and other documents,

The meanings of these four documents are:

user account information file , user password file , user group information file , user group password information file

Specific content can be opened to see, are text files, clear structure

Here is a specific word about the password information file,

Shadow files (including user passwords and group password files) personally think that you can understand:

It originally does not exist, that is, it is not with the user's operation and the simultaneous production,

This file is generated by MD5 encryption of the password field in the passwd file or group file, and the password field in the passwd file is MD5 encrypted and no longer fully displays the password.

Instead of the character ' X ',

Is it possible to temporarily cancel the encryption of the shadow file? Of course, the answer is yes,

With the pwunconv command, the encryption is temporarily canceled, and after the encryption is canceled, the shadow file will disappear temporarily,

The password will appear in the passwd or group file as a full string

Restore encryption using the PWCONV command,

After recovering the encryption, the shadow file will appear, and the password in the passwd file will be replaced by ' X ' again.

Knowledge about user information and passwords in Linux