I'm trying to backup my MacOS computer onto an USB key, and when I run the restore command from the Disk Utility app, I get an error 254 :
Validating target... Validating source... Source volumt format on device "/dev/disk0" is not valid for restoring Could not validate source - error 254 The operation failed
For information, the title is really odd since it shows Restoring to "My Usb Key" from "(null)" (sorry the text is approximative (it's originally in French), but the main point here is the "from null")
What is wrong with my usb key? (it's a 8Gb, Apple asked for a "more than 1gb").
Thank you for your help.