Docker Volumes and Bind Mounts -9

Volumes is nothing  but the docker storage

Docker has multiple storage drivers that allow one to work with the underlying storage devices. 

Technology	Storage Driver
OverlayFS	overlay or overlay2
AUFS	aufs
Btrfs	brtfs
Device Manager	devicemanager
VFS	vfs
ZFS	zfs

In Docker, you have a separate volume that can shared across containers. These are known as data volumes

features of data volume are −

• They are initialized when the container is created.
• They can be shared and also reused amongst many containers.
• They exist even after the container is deleted.

docker info 

The command will provide all relative information on the Docker component installed on the Docker Host.

Listing all the Volumes
You can also list all the docker volumes on a docker host.
docker volume ls
The command will output all the volumes on the dockerhost




Creating a Volume
docker volume create –-name=volumename –-opt options





Let me go inside the volume folder

docker inspect is used to see the details of this image

By default it creates _data folder inside the IBM Volume.

Now, i want to add some file in this volume. 

I want to create  a text editor so we need to use "vi"

Once,  you click on Enter, the below screen gets displayed.

Type letter i, to enter the details

After entering the below details , and the last we will be

using linux cmd that is ":wq!" , to go back to prev screen

Then, it will exit from that window and go back to prev scren

Now, Type ls to check the details inside that folder as shown below

To see, the details, use the below command

 cat project.details.txt

Now, let us create one container and attach that volume

docker run -idt --name 007test1 -v IBM:/IBM nginx

(Source/Destination)

I am taking the entire folder .

Run docker ps 

Now, we need to go inside that container. So run the below command.

docker exec -it 007test1 bash

Run ls 

After running cat cmd, i was able to see my details

If we want to create a directory also we can create. 

Now exit from that 

Let me create one more container with the same volume. 

docker run -idt --name rose -v IBM:/tmp/tmpnginx nginx:latest 

Next run docker ps command

Let us run that container by using exec command

Let me run the cat command

Let me create few folders inside this, with any names as shown below

Let me go to docker ps again

Now, both the containers are having different data, let me check the volumes

Now, let me go to the container



Now, let us delete those two containers and check, what will happens to my volumes
docker rm -f 62f0b9dd126f 817110eec58f

Now, those two containers have been deleted. But my data still exists. Let us check 

Now, again we can create a new container and have that volume of data  inside that container

docker run -idt --name starfish -v IBM:/var/ibm bash 

In the same way, we can create a container ,and assign to that particular volume

Next, I am going  to delete all the containers and check, if my volume data is lost or not

Than also i can see my volume of data.

Let me check the Volumes by running the command docker volume ls

We also have a  command docker volume prune , which will delete the volumes.

We can also delete the volume by using the rm command.

Folder Sharing

Let me first create a directory and add some sample txt file inside it.

Now, i have created two files 1 and 2 

Now, i want to create a container and attached this folder to it.

docker run -idt --name ab123 -v  /root/mystore:/mystore nginx:latest

Now, i am inside this container

Exit from that

I am able to read the data, outside container . the file which i have created inside 

container, i am able to view it

Let me delete the container.

Now, i have deleted the container, then also i can access the shared folder data.

FYI

By Default all the data of the container are stored in the writable container layer

This data only exists, while the container is active. If the container no longer exists or 

deleted  the data is also deleted along with the container.

Data on the writable layer in the container is written using a storage driver.

The writable container layer is tightly coupled to the host machine.