Does your Mac show cannot validate source error 254? Then you must take proper measures otherwise the condition would be even more complicated than ever. Sometimes due to unknown reasons or human fault there is error appears on Mac. There is one such incident reported while attempting certain task related to restoring external volumes on Mac error message as cannot validate source error 254 emerges. Whenever this type of condition arises then it is difficult to perform any task related to file transfer into external drive and most importantly it might be possible that you even lose the access other precious file too in such case. So as a smart Mac user your first priority should be fix cannot validate source error 254. You can try to repair disk permissions through using disk utility. But if the error consistently occurring case formatting the hard disk is mere alternative. However by doing this there is file deletion takes place but luckily with having Mac Data Recovery Software you do not further worry about it. It lets you to regain the access of all kind of lost file successfully and effectively. Hence, resolve cannot validate source error 254 as quick as possible.