Linux provides several different types of users

Linux stipulates three different types of users, namely: 1. Super user. The super user’s user name is root, which has all operating rights; 2. System user. The system user is responsible for the normal operation of the Linux system. The necessary built-in users are generally used for management services; 3. Ordinary users. Ordinary users are created to allow users to use Linux system resources. The accounts created by users are generally ordinary accounts.

#The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

Linux provides several different types of users?

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Brief description of Linux user types

Linux system is a multi-user and multi-tasking operating system. Each user Everyone has an independent identity number, which is the user ID (UID). In Linux, the user does not know the user's user name, but it actually knows the user ID—UID.

Users under Linux are divided into three categories: super user (root), system user, and ordinary user.

The user name of the super user is root, which has all operating rights. Therefore, for the sake of security, it is recommended not to easily operate files under the root account. In the character interface of the Linux operating system, the prompt for the root account is #, and by default, the UID of the root user is 0.

The system user is a built-in user necessary for the normal operation of the Linux system. It is generally used for management services. System users cannot be used to log in, such as bin, daemon, lp and other users. The UID of system users is generally 1~499, and their shell is /sbin/nologin.

Ordinary users are created to allow users to use Linux system resources. The accounts created by users are generally ordinary accounts. In the character interface of the Linux operating system, the prompt for ordinary users is $, and the default UID for ordinary users is 1000~60000.

Linux system also inherits the practice of Unix system, using plain text files to save various account information. Users can manage users and groups by modifying text files.

The user-related files are:

/etc/passwd (user account file, accessible to all accounts) 7 sections in total, The format is as follows:

Username: Password: UID: GID: Account information: Account directory: Shell version

/etc/shadow ( User password file (can only be accessed by root), with a total of 9 paragraphs, the format is as follows:

Username: Password: Number of days since the last modification: Minimum number of days between two password modifications: How many days will it take to change the password again? Change password: The number of days from when the warning is issued to the official expiration of the password: The number of days the username is still valid before the login is prohibited: The time the user is prohibited from logging in: Flag field, unintentionalmeaning

Note: shadow In the password field, * indicates that the user is prohibited from logging in, "!!" indicates that the user has not set a password, and "!" indicates that the user is locked.

The password of passwd is the shadow password represented by X, and the shadow is the encrypted and saved ciphertext.

The file related to the user group is:

/etc/group (user group file, accessible to all accounts) , a total of 4 paragraphs, the format is as follows:

User group name: Group password: GID: Group member

/etc/gshadow (User group Password file, which can only be accessed with root permission) There are 4 paragraphs in total, the format is as follows:

User group name: Group password: Group manager: Group member

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