Restore error 254 is quite a common issue that Mac users face which can lead to data loss. You may encounter this particular error message “Could not validate source error 254” on Mac. This error generally shows up when you try to mount a disk image on the Mac drive. This image file can be of any software or backup disk so they must be really important to you. The error can be due to corruption of disk image issue with the mounting process. You can use the disk utility to restore error 254 due to improper mounting process but if does not detect any problem then there must be corruption in disk image file. The corruption might be caused at the time of creating disk image like any interruption or error or it was infected by virus later. You may look for another copy of that image but if it is not available then you can use Mac data recovery software to recover disk image and restore error 254. The software is quite useful and it can be used quite easily by any user. It will recover the image in the intact state so that it can be mounted properly after being recovered. And this you will not get the error as also you can restore error 254 any time it occurs again on any other file.