The passwd command in Unix-like operating systems is used for changing user passwords. It provides various options for password management. This cheat sheet covers essential passwd commands for users and system administrators.

Introduction:

The passwd command is a crucial tool for managing user passwords on Unix-based systems. It allows users to change their own passwords and administrators to modify other user accounts.

Basic Commands:

CommandDescription
passwdChange the password for the current user.
passwd [username]Change the password for a specific user (requires sudo).
passwd -l [username]Lock the password of a user account.
passwd -u [username]Unlock the password of a previously locked account.
passwd -d [username]Delete the password of a user account (set to empty).

Password Policies:

CommandDescription
passwd -e [username]Expire the password of a user, forcing them to change it on next login.
passwd -n [min_days] [username]Set the minimum number of days between password changes.
passwd -x [max_days] [username]Set the maximum number of days a password is valid.

Administrative Commands:

CommandDescription
passwd -S [username]Display the password status (age, expire, etc.) for a user.
passwd -l -e [date] [username]Lock and expire a user account on a specific date.
passwd -S -aDisplay password status for all user accounts.
`passwd -S -aawk ‘$2 ~ /LK/ {print $1}’`

Security Tips:

CommandDescription
passwd --stdin [username]Set the password from standard input (useful for scripts).
passwd --warndays [days] [username]Set the number of days before a password expires to give a warning.
passwd --mindays [days] [username]Set the minimum number of days between password changes.
passwd --maxdays [days] [username]Set the maximum number of days a password is valid.

Miscellaneous:

CommandDescription
passwd --statusDisplay the password status for the current user.
passwd --helpDisplay help and usage information for passwd.

Conclusion

The passwd command is a fundamental tool for managing user passwords on Unix-like systems. This cheat sheet provides essential commands for users and administrators to change passwords, set password policies, and perform administrative tasks. Whether you are an individual user or a system administrator, these commands will help you effectively manage user passwords on your Unix-based system.