How to add users in linux

How to add users in Linux: 1. Use the adduser method to create a user, with syntax such as "sudo adduser alvin"; 2. Use useradd method to create a user, with syntax such as "sudo useradd alvin -m -d /home/alvin" ...".

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

linux How to add users?

Creation and deletion of users under Linux:

We mainly create users under Linux There are two ways: adduser and useradd. Their differences and main usage are as follows:

adduser

The usage of adduser is very simple, just adduser username is enough, as follows:

sudo adduser alvin

This command is actually a perl script, and its bottom layer still calls the useradd command. Many tutorials on the Internet say that it can perform human-computer interaction, but now some distributions (such as centOS) have actually improved it. No cumbersome interaction is required, and users can be created with just the above command.

The adduser command will automatically create the user's home directory and specify the shell version . However, some distributions will ask you to set a user password when creating a user, while others will not and require you to set the password manually.

The method to create a password for a user is as follows:

sudo passwd alvin

useradd

useradd is a relatively complex command, and it has a higher degree of freedom. If you just run useradd username, it will create a three-no user, namely: no user home directory, no specified shell version, and no password .

In order to successfully create a user, we also need to complete its parameters through some options. Commonly used options for the useradd command are as follows:

-c0f1f756d08d8d8bb31a584182f9cef6e: Add comment text. The remark text will be saved in the remark field of passwd;

-dccadea5c81f2e24170fa05400dbf9748: Specify the starting directory when the user logs in;

-D: Change the default value;

-e23b1e640ef96db2e864669f3fb316311: Specify the validity period of the account;

-fa2895cf32cfb674e78e57d82c0889104: Specify the number of days after the password expires to close the account ;

-gf43ae4ec324e0c754c0154614174d75e: specifies the group to which the user belongs;

-Gf43ae4ec324e0c754c0154614174d75e: specifies the additional group to which the user belongs;

-m: Automatically create the user's login directory;

-M: Do not automatically create the user's login directory;

-n: Cancel the creation of the user's login directory Group;

-r: Create a system account;

-s: Specify the shell used by the user after logging in;

-u: Specify user id.

For us ordinary users, the more commonly used options are the three marked in red above. For managers, all of the above options need to be mastered. We are currently focusing on the three options highlighted in red above. The

-d option is used to specify the user's home directory, which is the directory the user enters when logging in. For example: -d /home/alvin means that the specified user's home directory is /home/alvin. Usually the -d option is used together with the -m option. The -m option is used to automatically create the specified directory if it does not exist.

The -s option specifies the user's default shell version. If not set, its default version is /bin/sh. Therefore, the classic usage when we use useradd to create a new user is as follows:

sudo useradd alvin -m -d /home/alvin -s /bin/bash

In this way, the user can be successfully created, but there is still no password. The way to create a password is still to use the passwd command, which will not be described again here.

userdel

To delete a user, just "userdel username". It is best to delete the files it leaves on the system as well, which can be done using "userdel -r username".

sudo userdel -r alvin

Recommended study: "linux video tutorial"

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