Installing OS X or MacOS from old disk image files

What a pain in the tail. You tried to install Ubuntu on an old Mac Mini, then found that it really does not work well with all the devices (wireless) etc in the box. So you try to reinstall OS X on the machine. Well after you figure out how to make the install disks via the ‘createinstallmedia’ command

Inside the you will find in the Contents/Resources/ folder an application called createinstallmedia. This will make a USB drive into an install disk:

command to create the install USB is as follows:

<install file path>/<install>/Contents/Resources/createinstallmedia –volume <path and volume name of USB drive -> /Volumes/Blank> –applicationpath <install file path>/<install>

So if the your put your “Install” in the root and your USB is named “Blank” the command string would be:

/ –volume /Volumes/Blank –applicationpath /

Now comes the annoying part: Every time you create a disk, when you try to use it to reinstall the OS from the USB, that you just booted from because you know how to install the OS from the Recovery prompt….. you get the following “This copy of the Install OS X El Capitan application can’t be verified. It may have been corrupted or tampered with during downloading.”

What I ended up having to do it roll back the system date on the computer. To do this just open up the terminal from the command prompt and change the date with the date command (use a date that was not too far from the original date the OS was released).


To do this type:

$ date MMDDHHmmYY

MM – 2 digit month 01 – 12
DD – 2 digit date 01 – 31
HH – 2 digit hour 01 – 24
mm – 2 digit minute 01 – 59
YY – 2 digit year > 15


I set the date back to 0101111115 (Jan 1st at 11:11 am 2015) and suddenly the install USB is no longer corrupt… :)



Apple changed the command line from Mojave (10.14) forward. The only difference is that you no longer need the –application path argument. So from the above example:

/ –volume /Volumes/Blank

You may also need to sudo it to run now

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