Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Creating Big Sur Bootable USB - Not a valid OS installer app

A

ARK

macrumors 6502a
Original poster
Jul 20, 2008
539
103
Indianapolis, IN
As title states, Im trying to create the bootable USB using the "createinstallmedia" command in terminal. I've followed several directions including the one on Apple's site and all of them end with the "/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application."

This is the installer I'm using that downloaded from the software update window.

Terminal command I used is:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled

Any ideas here?
 
ResEdit_ResEdit said:
Does the installer app sit inside a protected folder or on a protected volume?
Click to expand...

It just sits in the Applications folder as it was downloaded.

Terminal command I used is:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled

Its the same command as shown on Apple's website for Big Sur: https://support.apple.com/en-us/HT201372
 
Last edited:
Just give it a try and click once on the installer (select it), do Copy (cmd c), klick on your desktop and do Paste (cmd v). Start again with installer sitting on your desktop with otherwise OK Terminal command:

sudo /Users/yourname/Desktop/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled
 
  • Love
Reactions: mudflap
ResEdit_ResEdit said:
Just give it a try and click once on the installer (select it), do Copy (cmd c), klick on your desktop and do Paste (cmd v). Start again with installer sitting on your desktop with otherwise OK Terminal command:

sudo /Users/yourname/Desktop/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled
Click to expand...

Well that worked. Though I will say it took a long time to finish out. I honestly think it worked before but I just didn't give it enough time to finish the job.
 
I had no problem getting the bootable installer onto an SD card connected through a Hub. The only trouble I had was getting the installer to work. There are some additional security measures that I had to disable by booting into recovery mode and using the Startup Security Utility to disable Secure Boot and Allow Booting from External Media. Without the setting, the installer failed to start.
 
I am glad I could help you out. Have you noticed that installer sitting in folder Application is write protected? In folder Desktop is not. That made the difference imho.
 
ARK said:
Well that worked. Though I will say it took a long time to finish out. I honestly think it worked before but I just didn't give it enough time to finish the job.
Click to expand...
Some USB thumbdrives are just awfully slow. I used to think the createinstallmedia command was slow until I ran it on a SATA SSD connected to the Mac via a USB 3.0 UAS adapter and the damn thing finished in 10 seconds. (Catalina).

If you find yourself doing installs and copies using thumbdrives often, it helps to invest in ones that have good transfer speeds. Lots of reviews out there, do the research. :)
 
  • Like
Reactions: Never mind and ARK
In my experience, the fastest USB flash key drives (and what I use to create USB installers) are the SanDisk Extremes and the Samsung BAR 128 GB drives. They have great write speeds and even better read speeds.

Using a generic no-name drive or other brand results in painfully slow installs in my experience.
 
  • Like
Reactions: ARK
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.
ARK said:
This one?

SanDisk Extreme Go USB 3.1 Flash Drive 64GB (SDCZ800-064G-G46) https://www.amazon.com/dp/B01NARBPI7/ref=cm_sw_r_cp_api_fabc_x6XSFb44W5XPR
Click to expand...
That will likely be much better than what you have, but the Extreme Pro series has the best performance. They cost a bit more, though.

Or, like myself, if you happen to have old SATA SSDs sitting around, buy one of these and use them as "thumbdrives". The speed will blow most thumbdrives away.

www.amazon.com

StarTech.com SATA to USB Cable - USB 3.0 to 2.5” SATA III Hard Drive Adapter - External Converter for SSD/HDD Data Transfer (USB3S2SAT3CB)

This SATA to USB cable is an external drive adapter that gives you quick and easy access to a SATA drive through the USB-A port on a laptop. This SATA solid-state (SSD) or hard drive (HDD) adapter lets you upgrade to an external 2.5"" SATA SSD or HDD. The cable lets you: add drive space,...
www.amazon.com
 
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.
  • Like
Reactions: ARK
ARK said:
This one?

SanDisk Extreme Go USB 3.1 Flash Drive 64GB (SDCZ800-064G-G46) https://www.amazon.com/dp/B01NARBPI7/ref=cm_sw_r_cp_api_fabc_x6XSFb44W5XPR
Click to expand...

That's a good one, I use this one as zorinlynx mentioned..

www.amazon.com

SanDisk 128GB Extreme PRO USB 3.2 Solid State Flash Drive - SDCZ880-128G-G46

With write speeds of up to 150MB/s, the SanDisk Extreme Go USB 3.1 Flash Drive lets you quickly copy and go. Up to 35X faster than standard USB 2.0 drives, so you can transfer a 4K movie to the drive in less than 40 seconds. The design keeps the retractable connector protected when not in use, an...
www.amazon.com

The Extreme Pro is about 2X the read speed of the Extreme Go..
 
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.
My guess is that the installer must be of a OS that is at or below the version you are running. I got the same message running Mohave and trying to use the Big Sur installer. I am going to upgrade the computer first and then try to create the bootable disk.
 
ResEdit_ResEdit said:
Just give it a try and click once on the installer (select it), do Copy (cmd c), klick on your desktop and do Paste (cmd v). Start again with installer sitting on your desktop with otherwise OK Terminal command:

sudo /Users/yourname/Desktop/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled
Click to expand...

Thank you so much. Totally worked for me, first try!
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back