Troubleshooting

Sierra-specific

There is an ongoing problem where the installer, if used with tools like AutoDMG, does not 'cleanly' unmount InstallESD.dmg post-execution. The symptom manifests itself with the following output:

Examining and verifying source...
Error: "hdiutil: attach failed - Resource busy
" while mounting InstallESD.dmg.

You can help by duping this bug, but in the meantime a quick way to 'heal thyself' is: First, find where on your system that mount is sticking around at: diskutil list Then, after finding the one that looks like this...

/dev/disk2 (disk image):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        +5.8 GB     disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:                  Apple_HFS OS X Install ESD        5.4 GB     disk2s2

...remove it by running the following (example, customize this to match what you see): hdiutil eject /dev/disk2