Mix phx.digest not working

I have a problem when i try to type this code in server :

_build/prod/rel/mywebapp/bin/mywebapp start

18:18:54.141 [error] Could not warm up static assets: could not find static manifest at “/var/www/myweb.com/mywebapp/_build/prod/rel/mywebapp/lib/mywebapp-0.1.0/priv/static/cache_manifest.json”. Run “mix phx.digest” after building your static files or remove the “cache_static_manifest” configuration from your config files.

The error gives you a hint: you have to manually run mix phx.digest (or rather programmatically as part of your build). phx_new adds a mix assets.deploy alias which you should use instead as it includes all the asset stuff that needs to be done.