I have tried once more.
Hopeless !
Always the same error message: "Failed to run shell script set_icon" and the iccon is lost.
Confirmation:
I have pasted the following text in the terminal, without removing anything.
Was I right ?
cp "/Volumes/Backup/.VolumeIcon.icns" "/Users/parents/Volume Icons/Backup.VolumeIcon.icns"
Thanks a lot for your patient help.
I appreciate.
Yours.