chpasswd Command in Linux

Introduction

In this guide, we'll delve into the Linux chpasswd utility, a powerful tool for systemadmin tasks, allowing for batch password modification. This tutorial covers grasping the fundamentals of the chpasswd command, implementing batch password changes, and automating these changes via shell scripts. This is especially beneficial in enterprise settings that require routine password updates for numerous users. You'll find practical examples and clear, step-by-step instructions to effectively manage user passwords within a Linux environment.

Understanding the chpasswd Command

This section focuses on demystifying the chpasswd command within Linux, a key tool for system administrators seeking to change passwords in bulk. The chpasswd command operates by reading username and password combinations from standard input and applying these updates to the system.

First, let's generate a file containing the user and password pairs we intend to modify:

labex:newpassword1
labuser:newpassword2

Next, we will invoke the chpasswd command to update the credentials for the listed users:

cat users_passwords.txt | sudo chpasswd

Example output:

labex:newpassword1
labuser:newpassword2

The chpasswd command processes the contents of the users_passwords.txt file, updating user passwords as specified. It's crucial to remember that passwords are transmitted in plain text using this method, necessitating its use only within secured environments and with appropriate caution. Using sudo allows a non-root user to execute the command with root privileges, which are required to modify other user's passwords. The systemadmin should be very careful when granting this right.

Automating Password Changes with Shell Scripts

In this final section, we will explore automating user password modifications through shell scripting. This technique proves invaluable for scenarios demanding regular password updates across a vast user base, common in larger organizations.

To begin, let's create a basic shell script utilizing the chpasswd command for password updates:

#!/bin/bash

## Define the list of users and their new passwords
users_and_passwords=(
  "labex:newpassword1"
  "labuser:newpassword2"
)

## Loop through the list and update the passwords
for user_and_password in "${users_and_passwords[@]}"; do
  user=$(echo "$user_and_password" | cut -d':' -f1)
  password=$(echo "$user_and_password" | cut -d':' -f2)
  echo "$user:$password" | sudo chpasswd
done

Save this script as update_passwords.sh within the ~/project directory and assign execute permissions:

chmod +x ~/project/update_passwords.sh

Now, execute the script to implement password changes for the specified users:

~/project/update_passwords.sh

Example output:

labex:newpassword1
labuser:newpassword2

The script iterates through the predefined user and password list, employing the chpasswd command to execute batch password updates.

Summary

This tutorial demonstrated the use of the chpasswd command in Linux for batch user password modification. We learned to create a file with user-password pairs and update passwords accordingly. We also explored automating these changes using shell scripts, particularly useful in corporate environments requiring frequent password updates for many users. The root user can manage and maintain the automated script.

Finally, you learned how to construct and execute a shell script leveraging the chpasswd command to streamline the user password update process. Remember the security implications of storing passwords as plain text.

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