Example of using supervisord in a container

Dockerfile

FROM debian:buster

# Install system dependencies
RUN apt update \
 && apt install -y \
        supervisor \
 && rm -rf /var/lib/apt/lists/*

COPY supervisord.conf /etc/supervisor/supervisord.conf

CMD ["/usr/bin/supervisord", "-c", "/etc/supervisor/supervisord.conf"]

supervisord.conf

[supervisord]
nodaemon=true

[program:proc_a]
command=python3 -m http.server
directory=/website

[program:proc_b]
command=/usr/bin/b

# Shut down supervisord if any process exits
# https://stackoverflow.com/a/64398319
[eventlistener:shutdown]
command=bash -c "echo READY; read LINE; echo Got event: $LINE >&2; kill -SIGQUIT $PPID"
events=PROCESS_STATE_STOPPED,PROCESS_STATE_EXITED,PROCESS_STATE_FATAL