Docker - 4

 Docker volume and how to share it

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-> Volume is simply a directory inside our container.

-> Firstly, we have to declare the directory as a volume and then share the volume.

->Even if we stop container, still we can access volume.

-> volume will be created in one container.

-> you can declare a directory as a volume only while creating conatiner.

-> you can not create volume in existing container.

->  you can share one volume across any number of containers.

-> volume will not be included when you update an image.

you can mapped volume in two ways

1. Container <---> container

2. Host <-----> container.

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1)Docker create( to create the container)

2)Docker start(to run the container)

3)Docker run( to create and start the container)

benefits of volume

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-> Decoupling container from storage

->share volume among different containers

-> Attach volume to containers

-> on deleting container volume does not delete.

Creating volume from Dockerfile.

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1. Create a Dockerfile and Write

FROM ubuntu

VOLUME ["/myvolume1"]

then create image from this dockerfile

docker build -t myimage .

Now create a container from this image & run

docker run -it --name container1 myimage /bin/bash

Now do ls, you can set myvolume1

Now share volume with another container

 

        Container1 <-------> container2

docker run -it --name container2 --privileged=true --volumes-from container1 ubuntu /bin/bash

                       (new)    (old)

Now after creating container2, myvolume1  is visible whatever you do in one volume, can see from other volume

touch /myvolume1/samplefile

docker start container1

docker attach container1

ls /myvolume1

you can see samplefile here.

exist

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Now, try to create volume by using command

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docker run -it --name container3 -v /volume2 ubuntu /bin/bash 

do ls --> cd /volume2

Now create one file cont3file and exist

Now create one more container, and share volume2

-> docker run -it --name container4 --privileged=true --volumes-from container3 ubuntu /bin/bash

Now you are inside container, do ls , you can see volume2

Now create one file inside this volume and then check in container 3, you can see that file.

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Volume (Host - Container)

-> verify files in  /home/jatin

-> docker run -it --name hostcont -v /home/jatin/rajput --privileged=true ubuntu /bin/bash

-> cd /rajput

Do ls, now you can see all files of host machine.

-> touch rajputfile (in container)

exist

Now check in host machine , you can see the files

see other commands

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--> docker volume ls

--> docker volume create <volumename>

--> docker volume rm <volumename>

--> docker volume prune

{it removed all unused docker volume}

-> docker volume inspect <volumename>

-> docker container inspect <containername>