Disk validator

The Disk-Validator is a program developed by Commodore for the standard file systems of the AmigaOS , which is loaded dynamically from diskette and automatically executed if a data carrier has been inserted whose file system is in an inconsistent state. The disk validator then automatically checks the data carrier and rebuilds the so-called bitmap block, which provides information on occupied and free blocks. This function is required because the standard Amiga file systems are not journaling file systems . This task of the disk validator corresponds to that of the Unix program fsck .

Up to Kickstart Version 1.3, the Disk-Validator can be found as an executable program in the L directory of a floppy disk or hard disk (L: Disk-Validator). Up to and including Kickstart Version 1.3 it has a file length of 1848 bytes.

The disk validator has been integrated in the Kickstart ROM since Kickstart Version 2.0 .

Some older Amiga viruses took advantage of the automatic execution of the disk validator in order to spread. They marked the root block of the host disk as not validated and overwritten the original disk validator with the virus code. When an infected floppy disk is inserted, the operating system checks the root block. Since the file system was marked as not validated, the disk validator on it was loaded and executed; however, this was the virus. Such viruses were only functional up to and including Kickstart version 1.3.