Storage and Volumes (10%)

Question 1

What is the pluggable architecture that Docker supports for the container writable layer storage?

Answer 1

Storage Drivers

Question 2

What is the preferred storage driver for all Linux distributions which need no extra configuration?

Answer 2

Overlay2

Question 3

Which device-mapper driver is used for production environments?

Answer 3

direct-lvm

Question 4

Which device-mapper driver is used for testing environments?

Answer 4

loopback-lvm

Question 5

How do you check the current storage driver information?

Answer 5

docker info

Question 6

How do you configure device-mapper?

Answer 6

// stop 
dockersudo systemctl stop docker

// set the device-mapper in /etc/docker/daemon.json file
{  "storage-driver": "devicemapper"}

//start 
dockersudo systemctl start docker

Question 7

What is the option that sets the direct-lvm for production device-mapper?

Answer 7

dm.directlvm_device

Question 8

What do you set the device-mapper and all configurable options in the daemon.json?

Answer 8

{
  "storage-driver": "devicemapper",
  "storage-opts": [
    "dm.directlvm_device=/dev/xdf",
    "dm.thinp_percent=95",
    "dm.thinp_metapercent=1",
    "dm.thinp_autoextend_threshold=80",
    "dm.thinp_autoextend_percent=20",
    "dm.directlvm_device_force=false"
  ]
}

Question 9

What are the different available storage options available for containers?

Answer 9

Block Storage
File System Storage
Object Storage

Question 10

Do containers create a writable layer on top of Image read-only layers?

Answer 10

Yes

Question 11

Where is the Docker’s local storage area?

Answer 11

/var/lib/docker/

Question 12

What is the difference between bind mounts and volumes?

Answer 12

Volumes are completely managed by docker

Bind Mounts are dependent on the host directory structure

Question 13

Volumes don’t increase the size of the containers. Is this statement correct and why?

Answer 13

Yes. Because volumes live outside of containers

Question 14

What should we use if we want to persist the data beyond the lifecycle of the containers?

Answer 14

Volumes

Question 15

How to create a Volume?

Answer 15

docker volume create my-volume

Question 16

How to list docker volumes?

Answer 16

docker volume ls

Question 17

How to inspect docker volume?

Answer 17

docker volume inspect my-vol

Question 18

How to remove docker volumes?

Answer 18

docker volume rm my-vol

Question 19

If you start a container with a volume that does not yet exist, Docker creates the volume for you. Is this statement correct?

Answer 19

Yes

Question 20

How to create a volume myvol2 with a docker run?

Answer 20

docker run -d \

• -name devtest \
• v myvol2:/app \
  nginx: latest

Question 21

How to verify the volume is created with the container?

Answer 21

// Look for the mounts sectiondocker inspect devtest

Question 22

How to create a volume with the –mount flag?

Answer 22

docker run -d \

• -name devtest \
• -mount source=myvol2,target=/app \
  nginx: latest

Question 23

How to remove all unused images not just dangling images?

Answer 23

docker system prune –all