Creating and Managing User Passwords in Linux

Managing users is a fundamental part of Linux administration. The process usually begins with creating a new user and then setting or changing their password. In this article, we will focus on two key aspects: creating new users and managing their passwords. We'll look at the commands involved, primarily useradd and passwd, and explore the various options you can use with these commands.

User Creation with useradd

The useradd command in Linux is used to create a new user. The basic syntax for creating a new user is:

sudo useradd [OPTIONS] USERNAME

You can replace USERNAME with the username you want to assign to the new user.

Example

To create a new user called alice, run:

sudo useradd alice

This will create a new user with the default settings. To set a password for this user, we use the passwd command, which we'll explore in detail below.

Managing Passwords with passwd

The passwd command is used to change the password for a user account. A superuser can change the password for any account, whereas a regular user can only change their own password.

Syntax

The basic syntax of the passwd command is:

passwd [OPTIONS] [USERNAME]

Options and Their Descriptions

Here's a table of commonly used options with the passwd command:

Option	Shorthand	Description
--delete	-d	Delete the password for the specified user.
--expire	-e	Force expire the user's password immediately.
--lock	-l	Lock the password of the specified account.
--unlock	-u	Unlock the locked password of the specified user.
--status	-S	Display the status of the user's password.

Example: Setting a Password

To set a password for the user alice:

sudo passwd alice

You will be prompted to enter the new password twice for confirmation.

Example: Deleting a Password

To delete a user's password:

sudo passwd -d alice

Example: Locking and Unlocking a User Account

To lock a user account:

sudo passwd -l alice

To unlock a user account:

sudo passwd -u alice

Example: Checking Password Status

To check the password status of a user:

sudo passwd -S alice

Listing Users and Their Permissions in Linux

Sometimes, as an administrator or even as a curious user, you may want to list the users and their permissions on your Linux system. Various commands and files can help you accomplish these tasks.

getent

One of the most reliable ways to list users is by using the getent command:

getent passwd

This command will list all the users along with some other details like home directory, default shell, etc.

/etc/passwd

Alternatively, you can also view the /etc/passwd file, which contains details of all user accounts:

cat /etc/passwd

Each line represents a user and contains information separated by colons.

Checking Permissions

ls -l

To check file or directory permissions, you can use the ls -l command followed by the file or directory name. For example:

ls -l /path/to/file

This will show you the permissions in the form -rwxr-xr-x, along with the owner and the group.

stat

Another command you can use is stat, which provides detailed information about files or directories, including permissions.

stat /path/to/file

id

To list a user's groups and other related information, you can use:

id [username]

Replace [username] with the user you want to check. If left blank, it will show information about the currently logged-in user.

/etc/group

The /etc/group file contains details about groups and their memberships:

cat /etc/group

Examples

To check permissions for a file named example.txt:

ls -l example.txt

To list all groups that a user named alice is a part of:

id alice

Summary

Managing user accounts and passwords are crucial tasks for system administrators. The useradd and passwd commands provide a range of options to create new users and manage their passwords effectively. Understanding these options and how to combine them is key to maintaining a secure Linux environment.

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