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Linux supports a special password protection technique by maintaining a shadow password file. A Shadow password file is a special version of password files that only root can read.
The password information is left out of the password file. You can determine weather the system users shadow password file by checking the password file. Type the following command on the command prompt.
# more /etc/passwd
It will display the content of the password file. Each line in the file represents information about a particular user. A colon (:) separates each information in a line. The second field is for password. If the password exists in the file then shadow password technique is not used by the system.
The shadow password technique can be implemented by converting the password file. You can do this by using the pwconv command. Log in as root and enter pwconv command at the prompt. It will not display any message, but when the shell prompt returns, your system will have a /etc/shadow file and /etc/passwd file encrypted password data is replaced with an x. The password data is now moved to /etc/shadow.
