Okay, my Macbook came with Lion. The internal hard drive has failed, so I got a new one, and when I try to install Lion via internet recovery it just gives me "This item is temporarily unavailable." for days now. It came with Lion, but it supports Sierra and when I installed Sierra I did have the presence of mind to save the InstallESD.dmg file to an external hard drive. So I've also tried to make a boot USB drive using InstallESD, by several means. I've copied the dmg file to the internal hard drive, and then used Disk Utility to format the USB drive (GUID partition table, single partition with Mac OS Extended file system), then Restore the dmg file to the formatted USB drive. This seems to work, but I can't get the Macbook to recognize the drive as bootable. I also have a Linux laptop and have tried making a boot drive by converting the dmg file to ISO, then doing the same thing. With the same results. Would appreciate any ideas. I've been stuck on this for days now. (Why does the internet restore not work?!? It has one job!) I also have the Sierra BaseSystem.dmg, if that's... useful for anything. If there was a SHA hash for InstallESD somewhere I could check it to see if it got corrupted.