how to debug docker

how to running (single)

• caddy

docker run -d --name caddy -p 2015:2015 caddy /caddy

• strace

pid && networkspace

docker run -t --pid=container:caddy --net=container:caddy --cap-add sys_admin --cap-add sys_ptrace  dalongrong/alpine-strace

with docker-compose

• start caddy service

docker-compose up -d caddy

• start alpine debug container

docker-compose up -d alpine

• inside alpine container && exec strace (or some utils)

ps -ef 
strace -p <pid>
pmap <pid>
....