A checksum is a calculation of all the data on a disk or disk image. You can use checksums to make sure that a disk image, CD, or DVD was copied correctly. Open Disk Utility for me. In the Disk Utility app on your Mac, choose Images > Add Checksum, then select the disk image to add the checksum to.

What is ADD checksum?

A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data integrity but are not relied upon to verify data authenticity.

How do you tell if your Mac is corrupted?

Reboot in single user mode by holding the Command + S during boot. When you see a prompt (should look like root # or something similar), type fsck -f and press Return . This is Mac's built-in filesystem consistency check tool and allows you to find and repair errors with the startup file system.