CODEWITHSUNDEEP
mongodbmacosdockerdocker-composedocker-volume
Narfanator
Narfanator

Reputation: 5813

Can't start mongo with docker command, but can with /bin/bash inside container (with data volume)

This docker-compose.yml:

services:
  database:
    image: mongo:3.2
    ports:
      - "27017"
    command: "mongod --dbpath=/usr/database"
    networks:
      - backend
    volumes:
      - dbdata:/usr/database

volumes:
  dbdata:

results in this error (snipped):

database_1  | 2016-11-28T06:30:29.864+0000 I STORAGE  [initandlisten] exception in initAndListen: 98 Unable to create/open lock file: /usr/database/mongod.lock errno:13 Permission denied Is a mongod instance already running?, terminating

Ditto for just trying to run the command in a container using that image directly:

$ docker run -v /usr/database mongo:3.2 mongod --dbpath=/usr/database

But, if I run /bin/bash when starting the container, and THEN start mongo, we're OK:

$ docker run -it -v /usr/database mongo:3.2 /bin/bash
root@8aab722fad89:/# mongod --dbpath=/usr/database

Based on the output, the difference seems to be that in the second scenario, the command is run as root.

So, my questions are:

  1. Why does the /bin/bash method work, when the others do not?
  2. How can I replicate that reason, in the docker-compose?

Note: On OSX, since that seems to effect whether you can mount a host directory as a volume for Mongo to use - not that I'm doing that.

Upvotes: 2

Views: 6728

Answers (1)

Wan B.
Wan B.

Reputation: 18835

To clarify, this image  hub.docker.com/_/mongo is an official MongoDB docker image from DockerHub, but NOT an official docker image from MongoDB.

Now to answer your questions,

Why does the /bin/bash method work, when the others do not?

This answer is based on Dockerfile v3.2. First to point out that your volume mount command -v /usr/database , is essentially creating a directory in the container with the root ownership permission.

Your command below failed with permission denied because the the docker image is running the command as user mongodb (see this dockerfile line) . As the directory /usr/database is owned by root. 

$ docker run -v /usr/database mongo:3.2 mongod --dbpath=/usr/database

While if you execute below /bin/bash then manually run mongod: 

$ docker run -it -v /usr/database mongo:3.2 /bin/bash

Your are logged in as root and executing mongod as root, and it has the permission to create database files in /usr/database/.

Also, if you're executing the line below, it works because you're pointing to a directory /data/db which the permission has been corrected for user mongodb (see this dockerfile line)

$ docker run -v db:/data/db mongo:3.2

How can I replicate that reason, in the docker-compose?

The easiest solution is to use command: "mongod --dbpath=/data/db" because the permission ownership has been corrected in the Dockerfile.

If you are intending to use a host volume, you probably would have to add mongodb user on your host OSX and change appropriate directories permission. Modifying the permission ownership of a volume mount is outside the scope of docker-compose.

Upvotes: 2

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