How to mount a host directory in a Docker container

Question

I am trying to mount a host directory into a Docker container so that any updates done on the host is reflected into the Docker containers.

Where am I doing somethin

Answer 1

Had the same problem. Found this in the docker documentation:

Note: The host directory is, by its nature, host-dependent. For this reason, you can’t mount a host directory from Dockerfile, the VOLUME instruction does not support passing a host-dir, because built images should be portable. A host directory wouldn’t be available on all potential hosts.

So, mounting a read/write host directory is only possible with the -v parameter in the docker run command, as the other answers point out correctly.

Answer 2

How do I link the main_folder to the test_container folder present inside the docker container?

Your command below is correct, unless your on a mac using boot2docker(depending on future updates) in which case you may find the folder empty. See mattes answer for a tutorial on correcting this.

docker run -d -v /Users/kishore/main_folder:/test_container k3_s3:latest

I need to make this run automatically, how to do that without really using the run -d -v command.

You can't really get away from using these commands, they are intrinsic to the way docker works. You would be best off putting them into a shell script to save you writing them out repeatedly.

What happens if boot2docker crashes? Where are the docker files stored?

If you manage to use the -v arg and reference your host machine then the files will be safe on your host.

If you've used 'docker build -t myimage .' with a Dockerfile then your files will be baked into the image.

Your docker images, i believe, are stored in the boot2docker-vm. I found this out when my images disappeared when i delete the vm from VirtualBox. (Note, i don't know how Virtualbox works, so the images might be still hidden somewhere else, just not visible to docker).

Answer 3

Using command-line :

docker run -it --name <WHATEVER> -p <LOCAL_PORT>:<CONTAINER_PORT> -v <LOCAL_PATH>:<CONTAINER_PATH> -d <IMAGE>:<TAG>

Using docker-compose.yaml :

version: '2'
  services:
    cms:
       image: <IMAGE>:<TAG>
       ports:
       - <LOCAL_PORT>:<CONTAINER_PORT>
       volumes:
       - <LOCAL_PATH>:<CONTAINER_PATH>

Assume :

• IMAGE: k3_s3
• TAG: latest
• LOCAL_PORT: 8080
• CONTAINER_PORT: 8080
• LOCAL_PATH: /volume-to-mount
• CONTAINER_PATH: /mnt

Examples :

1. First create /volume-to-mount. (Skip if exist)

$ mkdir -p /volume-to-mount

2. docker-compose -f docker-compose.yaml up -d

version: '2'
  services:
    cms:
       image: ghost-cms:latest
       ports:
       - 8080:8080
       volumes:
       - /volume-to-mount:/mnt

3. Verify your container :

docker exec -it CONTAINER_ID ls -la /mnt

Answer 4

Jul 2015 update - boot2docker now supports direct mounting. You can use -v /var/logs/on/host:/var/logs/in/container directly from your Mac prompt, without double mounting

Answer 5

Note that in Windows you'll have to provide the absolute path.

• Host: Windows 10
• Container: Tensorflow Notebook

Below worked for me.

docker run -t -i -v D:/projects/:/home/chankeypathak/work -p 8888:8888 jupyter/tensorflow-notebook /bin/bash

Answer 6

Here's an example with a Windows path:

docker run -P -it --name organizr --mount src="/c/Users/MyUserName/AppData/Roaming/DockerConfigs/Organizr",dst=/config,type=bind organizrtools/organizr-v2:latest

As a side note, during all of this hair pulling, having to wrestle with figuring out, and retyping paths over and over and over again, I decided to whip up a small AutoHotkey script to convert a Windows path to a "Docker Windows" formatted path. This way all I have to do is copy any Windows path that I want to use as a mount point to the clipboard, press the "Apps Key" on the keyboard, and it'll format it into a path format that Docker appreciates.

For example:

Copy this to your clipboard:

C:\Users\My PC\AppData\Roaming\DockerConfigs\Organizr

press the Apps Key while the cursor is where you want it on the command-line, and it'll paste this there:

"/c/Users/My PC/AppData/Roaming/DockerConfigs/Organizr"

Saves a lot to time for me. Here it is for anyone else who may find it useful.

; --------------------------------------------------------------------------------------------------------------
;
; Docker Utility: Convert a Windows Formatted Path to a Docker Formatter Path
;                   Useful for (example) when mounting Windows volumes via the command-line.
;
; By:       J. Scott Elblein
; Version:  1.0
; Date:     2/5/2019
;
; Usage:    Cut or Copy the Windows formatted path to the clipboard, press the AppsKey on your keyboard
;           (usually right next to the Windows Key), it'll format it into a 'docker path' and enter it
;           into the active window. Easy example usage would be to copy your intended volume path via
;           Explorer, place the cursor after the "-v" in your Docker command, press the Apps Key and
;           then it'll place the formatted path onto the line for you.
;
; TODO::    I may or may not add anything to this depending on needs. Some ideas are:
;           
;           - Add a tray menu with the ability to do some things, like just replace the unformatted path
;               on the clipboard with the formatted one rather than enter it automatically.
;           - Add 'smarter' handling so the it first confirms that the clipboard text is even a path in
;               the first place. (would need to be able to handle Win + Mac + Linux)
;           - Add command-line handling so the script doesn't need to always be in the tray, you could
;               just pass the Windows path to the script, have it format it, then paste and close.
;               Also, could have it just check for a path on the clipboard upon script startup, if found
;               do it's job, then exit the script.
;           - Add an 'all-in-one' action, to copy the selected Windows path, and then output the result.
;           - Whatever else comes to mind.
;
; --------------------------------------------------------------------------------------------------------------

#NoEnv
SendMode Input
SetWorkingDir %A_ScriptDir%

AppsKey::

    ; Create a new var, store the current clipboard contents (should be a Windows path)
    NewStr := Clipboard

    ; Rip out the first 2 chars (should be a drive letter and colon) & convert the letter to lowercase
    ; NOTE: I could probably replace the following 3 lines with a regexreplace, but atm I'm lazy and in a rush.
    tmpVar := SubStr(NewStr, 1, 2)
    StringLower, tmpVar, tmpVar

    ; Replace the uppercase drive letter and colon with the lowercase drive letter and colon
    NewStr := StrReplace(NewStr, SubStr(NewStr, 1, 2), tmpVar)

    ; Replace backslashes with forward slashes
    NewStr := StrReplace(NewStr,  "\", "/")

    ; Replace all colons with nothing
    NewStr := StrReplace(NewStr, ":", "")

    ; Remove the last char if it's a trailing forward slash
    NewStr :=  RegExReplace(NewStr, "/$")

    ; Append a leading forward slash if not already there
    if RegExMatch(NewStr, "^/") == 0
        NewStr :=  "/" . NewStr

    ; If there are any spaces in the path ... wrap in double quotes
    if RegExMatch(NewStr, " ") > 0
        NewStr :=  """" . NewStr . """"

    ; Send the result to the active window
    SendInput % NewStr