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Linux passwd Command: Change User Password

The passwd command is a Linux utility for managing user passwords. It allows users to change their passwords, while administrators can update, lock, or unlock user accounts. In this tutorial, we'll go over some common use cases for the passwd command.

Change your password:

To change your own password, simply run the passwd command with no arguments:

passwd

You will be prompted to enter your current password, followed by the new password, and a confirmation of the new password.

Change another user's password (requires root privileges):

If you're an administrator (root user) or have the appropriate permissions, you can change another user's password. To do this, use the passwd command followed by the target username:

sudo passwd username

Replace "username" with the appropriate user account. You will be prompted to enter a new password and confirm it.

Lock a user's account:

To lock a user account, which prevents them from logging in, use the passwd command with the --lock flag:

sudo passwd --lock username

Replace "username" with the user account you want to lock. This command will prepend an exclamation mark ! to the password field in the /etc/shadow file, effectively disabling the account.

Unlock a user's account:

To unlock a previously locked user account, use the passwd command with the --unlock flag:

sudo passwd --unlock username

Replace "username" with the user account you want to unlock. This command will remove the exclamation mark ! from the password field in the /etc/shadow file, re-enabling the account.

Set password expiration:

You can set the password expiration date for a user account with the chage command. To force a user to change their password every 90 days, for example, run:

sudo chage -M 90 username

Replace "username" with the appropriate user account.

Display password aging information:

To display the current password aging information for a user account, use the chage command with the -l flag:

sudo chage -l username

Replace "username" with the appropriate user account. This command will display information such as the date the password was last changed, the password expiration date, and the number of days before the password expires.

That's it! This tutorial provided an overview of the passwd command and some of its common use cases. For more advanced usage and a complete list of options, refer to the passwd man page by running man passwd in your terminal.

How to use passwd to change user passwords: To change your own password, simply run:
```
passwd
```
Changing user passwords in Unix-like systems with passwd: Use passwd followed by the username to change another user's password:
```
sudo passwd username
```
Managing user authentication with passwd in Linux: passwd is a vital tool for managing user authentication. Administrators can use it to change user passwords and set policies:
```
sudo passwd username
```
Setting password policies using passwd in the terminal: Password policies can be set using passwd. For example, to set a minimum password length:
```
sudo passwd --minlen=8 username
```
Advanced options for the passwd command in Linux: passwd has advanced options. For instance, expire a user's password:
```
sudo passwd --expire username
```
Force password change with passwd in Linux: Force users to change their password at the next login using passwd:
```
sudo passwd --expire username
```
Changing root password using passwd in Ubuntu/Linux: To change the root password, use sudo passwd root and follow the prompts:
```
sudo passwd root
```