Create or update passwords for existing users in Linux – passwd

guidesecurity

The `passwd` package in Linux is a command-line tool used to create or update passwords for existing user accounts. It’s an essential utility for maintaining system security by allowing users and administrators to manage passwords effectively.

The `passwd` package is crucial for securing user accounts by enabling strong password settings and regular updates. Common uses include user password resets and system administrators managing passwords across multiple accounts.

Written in C, `passwd` is typically included as a core utility in most Linux distributions.

Official Page of `passwd`

You can find the official documentation for `passwd` at this link: https://man7.org/linux/man-pages/man1/passwd.1.html

Installation

In most Linux distributions, `passwd` comes pre-installed. If it’s missing, you can install it using your distribution’s package manager.

Installing `passwd` on Ubuntu/Debian

Open a terminal and run:

sudo apt-get install passwd

Installing `passwd` on CentOS/RHEL

Open a terminal and run:

sudo yum install passwd

Common `passwd` Commands

Here are some of the most frequently used `passwd` commands:

1. `passwd`

Changes the password for the currently logged-in user. You’ll be prompted for your current password, followed by the new password.

2. `passwd [username]`

Changes the password for the specified user (requires appropriate permissions, usually root). You’ll be prompted for the new password.

3. `passwd -l [username]`

Locks the specified user’s account. The user will not be able to log in using their password. Requires root privileges.

4. `passwd -u [username]`

Unlocks a previously locked user account. The user will be able to log in using their password again. Requires root privileges.

5. `passwd -d [username]`

Removes the password for the specified user. The user will be able to log in without a password. This is generally discouraged for security reasons. Requires root privileges.

Similar Packages

Other packages provide similar or related functionality:

• `chpasswd`: Useful for updating passwords in batch mode using a file containing username/password pairs.
• `usermod`: A more general utility for modifying user account settings, including password policies and expiry.
• `chage`: Specifically designed for managing password expiry information for users.

Example Scripts

Here are example scripts demonstrating automated `passwd` usage:

1. Script to change passwords for multiple users

#!/bin/bash

users=("user1" "user2" "user3")

for user in "${users[@]}"
do
  echo "Changing password for $user"
  sudo passwd "$user"  # Requires sudo for non-current user
done

This script iterates through a list of users and prompts for a new password for each. Note: This script will require `sudo` and potentially interaction to enter the new passwords. A less interactive approach would use `chpasswd`.

2. Script to lock user accounts

#!/bin/bash

users=("user1" "user2" "user3")

for user in "${users[@]}"
do
  echo "Locking account for $user"
  sudo passwd -l "$user"
done

This script locks the specified user accounts, preventing login.

3. Script to unlock user accounts

#!/bin/bash

users=("user1" "user2" "user3")

for user in "${users[@]}"
do
  echo "Unlocking account for $user"
  sudo passwd -u "$user"
done

This script unlocks the specified user accounts, allowing login.

List of `passwd` Functions and Constants

Conclusion

The `passwd` package is a fundamental tool in Linux for managing user account passwords. It allows users and administrators to control access to the system. Understanding its commands and options is crucial for maintaining a secure Linux environment. From changing individual passwords to locking and unlocking accounts, `passwd` provides the necessary functionality for basic user account management.

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