Docker&Celery - ERROR: Pidfile (celerybeat.pid) already exists

Another solution (taken from https://stackoverflow.com/a/17674248/39296) is to use --pidfile= (with no path) to not create a pidfile at all. Same effect as Siyu's answer above.

I believe there is a pidfile in your project directory ./ then when you run the container, it's mounted in. (therefore RUN find . -type f -name "celerybeat.pid" -exec rm -f {} \; had no effect).

You can use celery --pidfile=/opt/celeryd.pid to specify a non mounted path so that it is not mirror on the host.

Although not professional in the slightest, I found adding:

celerybeat.pid

to my .dockerignore file was what fixed said issues.