Linux /etc/shadow File Hack and crack

The /etc/shadow is a text-based password file. The shadow file stores the hashed passphrase (or “hash”) format for Linux user account with additional properties related to the user password. This shadow file is directly accessible only to the root user. However, some commands or programs (e.g., su, passwd, and others) with unique SetUID (SUID) are set on them to grant them access to the shadow file. Understanding /etc/shadow file format is essential for sysadmins and developers to debug user account issues.

Basically, the /etc/shadow file stores secure user account information. All fields are separated by a colon (:) symbol. It contains one entry per line for each user listed in /etc/passwd file.