Git server side hooks commit update file

Question

I am trying to implement git hook commit on a server using these instructions: https://git-scm.com/book/be/v2/Customizing-Git-An-Example-Git-Enforced-Policy

I created file "update" (make it executable, put in hooks folder), and found that this file is not executed when I do git commit -m "my message" and git push - all these commands work perfectly, but 'update' file is not working (I tried with simple script "echo "Hello World" >> somefile.txt)

Where is the problem?