After running "find . -mount | cpio -pvdm /Applications/Install\ macOS\ High\ Sierra.app/Contents/SharedSupport" command it uses ALL of my disc space on my HD, then ends with "Write failed: No space left on device"
Any way to fix this??
Hey, before you run that command make sure you're in the directory "/macOS Install Data" you can go to it by copying and pasting:
Note: Keep the quotes around the directory name, there's spaces so you won't have to escape them with funky slashes like the OP did.
You can verify this is your current directory by using the command pwd (present working directory). Should look like this:
$ pwd
/macOS Install Data
The reason you're most likely running out of disk space is because you're trying to copy whatever your present directory is. For example your home folder perhaps, maybe even the root which is your entire hard drive contents!
If you get a message saying that the directory /macOS Install Data doesn't exist, then don't proceed with the find . -mount [...] command. You can make sure this directory exists and has contents by carefully following OPs instructions, and abandoning the install process at the end before reboot.
PS.
You can also verify the size of the download by running this command in the "/macOS Install Data" directory.
$ du -h
0B ./Locked Files/Boot Files
20K ./Locked Files
4.9G .