This sucks when it happens I know. I've had this happen when creating a USB installer from a Mac OS DMG that was downloaded with Safari. For some reason safari treats certain files differently especially iPhone firmware but also in some cases Mac OS dmg's. Don't ask me why because I can't remember the info since it was so long ago when I read it. Download the DMG with Firefox or Chrome and then Recreate the Installer USB. Stuff happens and DMG's get corrupted so my "go to" when creating a USB installer and things go wrong is to redownload the DMG and don't use Safari. Once you've rooted out that the DMG is good then you can move on to all the other helpful suggestions. Good luck! Oh and once you get that installer working HIDE IT FOR NEXT TIME SO THAT YOU DON'T ERASE IT HA HA!

If you have a working Mac and you aren't Terminal Savvy then just use DiskMaker X to create the bootable USB installer.

This sucks when it happens I know. I've had this happen when creating a USB installer from a Mac OS DMG that was downloaded with Safari. Before we start you need to MAKE SURE you are creating an installer USB from a Mac OS Sierra installer that is around 5.2GB. If you are trying to do it from one downloaded from the App store that is smaller than that then you are downloading an incomplete installer meant to be used only for upgrading within the Operating system (i.e. clicking on it in the Applications folder to install)

Here is a link on how to download the actual "Full" installer:

https://mycyberuniverse.com/macos/how-download-complete-macos-high-sierra-installer-app.html

So to continue. For some reason safari treats certain files differently especially iPhone firmware but also in some cases Mac OS dmg's. Don't ask me why because I can't remember the info since it was so long ago when I read it. Download the DMG with Firefox or Chrome and then Recreate the Installer USB. Stuff happens and DMG's get corrupted so my "go to" when creating a USB installer and things go wrong is to redownload the DMG and don't use Safari. Once you've rooted out that the DMG is good then you can move on to all the other helpful suggestions. Good luck! Oh and once you get that installer working HIDE IT FOR NEXT TIME SO THAT YOU DON'T ERASE IT HA HA!

If you have a working Mac and you aren't Terminal Savvy then just use DiskMaker X to create the bootable USB installer.

This sucks when it happens I know. I've had this happen when creating a USB installer from a Mac OS DMG that was downloaded with Safari. For some reason safari treats certain files differently especially iPhone firmware but also in some cases Mac OS dmg's. Don't ask me why because I can't remember the info since it was so long ago when I read it. Download the DMG with Firefox or Chrome and then Recreate the Installer USB. Stuff happens and DMG's get corrupted so my "go to" when creating a USB installer and things go wrong is to redownload the DMG and don't use Safari. Once you've rooted out that the DMG is good then you can move on to all the other helpful suggestions. Good luck! Oh and once you get that installer working HIDE IT FOR NEXT TIME SO THAT YOU DON'T ERASE IT HA HA!

This sucks when it happens I know. I've had this happen when creating a USB installer from a Mac OS DMG that was downloaded with Safari. For some reason safari treats certain files differently especially iPhone firmware but also in some cases Mac OS dmg's. Don't ask me why because I can't remember the info since it was so long ago when I read it. Download the DMG with Firefox or Chrome and then Recreate the Installer USB. Stuff happens and DMG's get corrupted so my "go to" when creating a USB installer and things go wrong is to redownload the DMG and don't use Safari. Once you've rooted out that the DMG is good then you can move on to all the other helpful suggestions. Good luck! Oh and once you get that installer working HIDE IT FOR NEXT TIME SO THAT YOU DON'T ERASE IT HA HA!

If you have a working Mac and you aren't Terminal Savvy then just use DiskMaker X to create the bootable USB installer.