ERROR in ngcc is already running at process with id 5196

Try deleting your ngcc_lock_file in the path: node_modules/@angular/compiler-cli/ngcc/ngcc_lock_file.

Or for Angular 9, the lock file to delete is node_modules/@angular/compiler-cli/ngcc/__ngcc_lock_file__.

I had the same issue and I and deleted that file and it started working for me.

I hope it helps!

 rm node_modules/@angular/compiler-cli/ngcc/__ngcc_lock_file__

Working Solution

Delete all node modules
Close any working terminal or you can shut down your PC if you cant make sure that you've closed all working terminals
run npm i to setup your modules
run ng s

It's working with me well !

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