Install macOS High Sierra.app does not appear to be a valid OS installer application I downloaded High Sierra from the App Store, then tried creating a USB installer using Terminal but I get the following error:
# sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/My-USB-Name/ --applicationpath /Applications/Install\ macOS\ High\ Sierra.app 

/Applications/Install macOS High Sierra.app does not appear to be a valid OS installer application.

The High Sierra directory is present, I'm able to press tab on my keyboard to auto-complete the paths.
After Googling the error, I found this Reddit answer, but I'm not sure what he's talking about or why it should be done, so I haven't tried it.

&quot;Move the directory /macOS Install Data (which is downloaded after you run through the installation once) to be Install macOS High Sierra.app/Contents/SharedSupport&quot;

The USB I'm using is 64Gb and freshly formatted using Disk Utilities.
These answers didn't help solve my issue. I think I have the &quot;stub&quot; in my Applications folder as the High Sierra .app is only 14MB.
I can't figure out how to install the full High Sierra installer
My specifications:
sh-3.2# system_profiler SPSoftwareDataType
Software:

    System Software Overview:

      System Version: OS X 10.8.5 (12F45)
      Kernel Version: Darwin 12.5.0
      Boot Volume: lily
      Boot Mode: Normal
      Computer Name: lily’s MacBook Air
      User Name: System Administrator (root)
      Secure Virtual Memory: Enabled
      Time since boot: 12:37
Here's what you need to do (example follows High Sierra):


Format a USB stick with format Mac OS Extended, scheme GUID Partition Map and name it Untitled
Get and run the installer from https://support.apple.com/en-us/HT208969
Run through the installer all until you are asked to restart, but then exit the installer
sudo mkdir /Applications/Install\ macOS\ High\ Sierra.app/Contents/SharedSupport
sudo cp -R /macOS\ Install\ Data/ Applications/Install\ macOS\ High\ Sierra.app/Contents/SharedSupport/
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled


And... if you get an error while installing OSX, e.g. "Installer resource error", then follow these step:


ctrl+command+shift+alt+H and open the Terminal
cp -rf /Volumes/Install\ macOS\ High\ Sierra/Install\ macOS\ High\ Sierra.app/Contents/SharedSupport/* /Volumes/Untitled/macOS\ install\ data/
Reboot!


You're welcome!