Docker container mongod error when starting via ss

问题:

I have installed mongodb on a docker container together with openssh on ubuntu 14.04. The container is running with ssh but when I ssh into the container I get the following error when trying to start mongod.

root@430f9502ba2d:~# service mongod start
Rather than invoking init scripts through /etc/init.d, use the service(8)
utility, e.g. service mongod start

Since the script you are attempting to invoke has been converted to an
Upstart job, you may also use the start(8) utility, e.g. start mongod

Also start mongod does not affect anything.

Tried looking at this also Mongo daemon doesn't run by service mongod start without it helping.

mongod --config /your/path/to/mongod.conf doesn't seem to work also, just locks up.

The error below is standard as of course there is no mongod server running.

root@430f9502ba2d:/# mongo
MongoDB shell version: 2.6.9
connecting to: test
2015-05-07T20:49:56.213+0000 warning: Failed to connect to 127.0.0.1:27017, reason: errno:111 Connection refused
2015-05-07T20:49:56.214+0000 Error: couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed at src/mongo/shell/mongo.js:146
exception: connect failed

回答1:

The problem here is your approach. Docker does not have an init system like you are used to on traditional systems. What docker does is replace PID 1 with the process you specify in the CMD or ENTRYPOINT Dockerfile commands. For now, ignore ENTRYPOINT, because it replaces what your CMD is run with (normally, it's /bin/sh -c). You need to instruct docker to start your mongod service in your Dockerfile with the CMD command, like:

CMD usr/bin/mongod

And when you run your container, mongod will be your PID 1. Now, you're probably wondering at this point "But what about my SSH server?" and the answer is: Don't run an SSH server on your docker containers. There are some use cases where running an SSH server is okay, but almost all of the "normal" reasons (debug, C&C, etc) are nullified with the "best practice" for getting a shell on your container:

docker exec -it myContainer /bin/bash

This will drop you into a shell on your running container. The recommendation here for managing configuration and changes in your docker container is to use something like Ansible. However, remember that docker containers are ephemeral, and you shouldn't be restarting services and changing configuration state on them. If you need a config change, change the Dockerfile or config data, and then start a new container. Good luck! Here is a little more information on Dockerizing MongoDB, but keep in mind that the method described there alters the ENTRYPOINT in the Dockerfile, which is a little more involved and requires a better understanding of what's going on in Dockerfiles.

回答2:

This is really helpful. I was trying to make old Ansible playbooks work with Docker by creating several blank containers and let Ansible do the rest.

It works through command mongod --dbpath /var/lib/mongodb --smallfiles