CODEWITHSUNDEEP
dockercontainersdocker-volume
BRZ
BRZ

Reputation: 13

Strange issue about applying docker named volume for new container

As I understand from all the information I found, the docker host volume can be created from three ways:

1- by ignoring the host-path (it will automatically create a directory with random ID)

2- by specify the host-path (it will also automatically create a directory with random ID)

3- by named volume and specify to a host-path

So I was trying first 2 ways:

$ docker run --name mongo-docker -v /data/db -p 27017:27017 -d mongo
$ docker run --name mongo-docker2 -v $(pwd)/data/:/data/db -p 27222:27017 -d mongo

And I look at the docker volume list:

$ docker volume ls

DRIVER    VOLUME NAME
local     5b829a731245cb7fe3a1f28aca4c4c3c3791105be228182ccb9b2f72319180c8
local     fb058e804412fb56b2096e2cb903e3ae73647ef6ca076ad9003708b80f94ffc5

It looks just what I was expected.

But when I tried the last one, by created first a volume:

$ docker volume create mongoVol
mongoVol

$ docker volume ls
DRIVER    VOLUME NAME
local     mongoVol

and use it for host-volume path, came up like this:

$ docker run --name mongo-docker3 -v mongoVol:/data/db -p 27322:27017 -d mongo
86bea0e52c9f395268665e191edc59f795d07266f17667502c7fa32879a6e021

$ docker volume ls
DRIVER    VOLUME NAME
local     0de25c92be504d0a6b9bb9c83aa8a6fe17bf9bc195562314ca49edb1c4cf4377   <=== create a new one for new container?
local     mongoVol

Why is this create a new directory for it? Shouldn't it be just the "mongoVol" volume?

I can’t find answers to related questions on any forum, post nor any videos....

Upvotes: 1

Views: 148

Answers (1)

David Maze
David Maze

Reputation: 158647

The mongo image's Dockerfile has two directories named in a VOLUME statement. You're mounting content on /data/db but not on /data/configdb.

If the Dockerfile declares a directory as a VOLUME and nothing is explicitly mounted there, Docker automatically creates an anonymous volume (your first case). That's what results in the additional volume appearing in the docker volume ls listing.

Upvotes: 1

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