Introduction

• The first thing you should do upon logging into a system for the first time is: change your password.
• Passwords are very important for security, especially in a "networked" environment.
• The UNIX command to change your password is passwd.
• It will ask for your current password before allowing you to change it.
• As with logging in, passwords will not be printed to your screen.
• It will ask for the new password twice to make sure you typed it right:

  
  	% passwd
  	passwd:  Changing password for kns
  	Enter login password: 
  	New password: 
  	Re-enter new password: 
  	passwd (SYSTEM): passwd successfully changed for kns
  	% 
  
  

• Depending on setup, this command may not work. If it doesn't work, see your sys-admin.
• It is very important to choose a good password:
  • Never make it your username.
  • Avoid dictionary words.
  • Avoid dictionary words spelled backwards.
  • Try to include numbers, mix up letter case, etc.
  • Passwords can be as long as you want but most UNIXes only pay attention to the first 8 characters.
• Change your password frequently.

References

1. http://en.wikipedia.org/wiki/Password
2. http://www.h-online.com/security/news/item/Crypto-tool-predicts-password...
3. https://www.hammerofgod.com/passwordcheck.aspx