Linux is an operating system kernel that lets you write programs for the computer. Linux is available for many types of computers and software, with most of its code being used to run the GNU operating system.
Shadow files are used in Linux to store encrypted versions of a corresponding file. The location where these files are stored depends on how the system installed, but it is usually in /etc/shadow under a file name ending with .pwd or .gdb.pwd/.gdb. This is because of the fact that these files are password protected, to prevent other users from viewing sensitive information.
How linux Shadow file format works
1. Linux has the ability to store encrypted passwords in a file called the shadow password file. If a user encrypts his or her password, then it cannot be recovered if forgotten. This is because the encrypted form of the password is stored in a shadow file, which is owned by root and not readable by normal users.
2. A shadow file is always owned by root. Only root can read its contents, as it assumes the owner of the file to be himself or herself.
3. User passwords are written using base64 characters in an encrypted form. This means that a password is written for a user in one base64 string. The shadow file does not hold plaintext passwords, and only the encrypted version of it.
Shadow file recovery methods
1. A shadow file is easy to recover: just type the correct password in. No matter how it was encrypted, the system will accept it and unlock the shadow file.
2. The system will ask you for a new password, but you don’t need to provide one; just restart the computer and log in again.
3. If there are no more passwords left on the system, you can use one of these methods to recover your old passwd (the one encrypted once) and/or remove it safely from your system:
4. There is no ‘un-decrypt’ function in Linux, so if you forget your password after logging into a Linux box, then all hope is lost!
5. Some distributions of Linux have poor security, and you can use simple brute-force methods to try all passwords until the right one is found.
Linux is one of the most powerful operating systems available and can be used to run almost anything imaginable. The shadow file allows you to store sensitive information safely, without the need for a password. It is a simple way of protecting valuable information against corruption or loss in case the system should crash or be lost.