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passwd.md

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Here's a concise explanation for the passwd command in Linux, including options, usage, and a short explanation:

passwd Command Cheatsheet

The passwd command is used to change a user's password in Linux. It can be used by both normal users to change their own password and by the system administrator to manage passwords for other users.

Basic Usage

  • Syntax:

    passwd [options] [username]

  • Examples:

    passwd
    • Prompts the current user to change their password.
    sudo passwd username
    • Changes the password for the specified username (requires superuser privileges).

Common Options

  • -l or --lock:

    • Locks the password of the specified user, effectively disabling their account.
    sudo passwd -l username
    • Locks the account of username, preventing them from logging in.

  • -u or --unlock:

    • Unlocks the password of the specified user, re-enabling their account.
    sudo passwd -u username
    • Unlocks the account of username, allowing them to log in again.

  • -d or --delete:

    • Deletes the password for the specified user, making it impossible to log in using a password.
    sudo passwd -d username
    • Deletes the password for username, allowing login only via other authentication methods.

  • -e or --expire:

    • Forces the user to change their password at the next login.
    sudo passwd -e username
    • Expires the password for username, requiring a password change at the next login.

  • -x [days] or --maxdays [days]:

    • Sets the maximum number of days a password is valid before it must be changed.
    sudo passwd -x 90 username
    • Sets the password for username to expire after 90 days.

  • -n [days] or --mindays [days]:

    • Sets the minimum number of days before a user can change their password again.
    sudo passwd -n 7 username
    • Prevents username from changing their password for 7 days after the last change.

  • -w [days] or --warndays [days]:

    • Sets the number of days before password expiration that the user will be warned.
    sudo passwd -w 7 username
    • Warns username 7 days before their password expires.

  • --help:

    • Displays help information about the passwd command.
    passwd --help
    • Shows usage information and available options.

Quick Tips

  • Changing Your Own Password:

    • Simply type passwd and follow the prompts to change your password.
    passwd
    • Prompts you to enter your current password and the new password.

  • Forcing a Password Change:

    • Use -e to require a user to change their password at the next login.
    sudo passwd -e username
    • Forces username to change their password upon the next login.

  • Locking and Unlocking Accounts:

    • Use -l to lock and -u to unlock user accounts.
    sudo passwd -l username
    • Locks the username account, preventing login.

  • Setting Password Expiration:

    • Control how often users must change their passwords with -x and -n options.
    sudo passwd -x 60 -n 1 username
    • Requires username to change their password every 60 days, with at least 1 day between changes.

Summary

The passwd command is essential for managing user passwords on a Linux system. It allows users to change their own passwords and administrators to enforce password policies, such as expiration and account locking. Proper use of passwd ensures secure and controlled access to user accounts.