Volumes

Question 1

What are Volumes?

Answer 1

The way the filesystem of a docker container is stored and used

Question 2

Each volume act like a separate ___

Answer 2

Drive

Question 3

What are the types of volumes?

Answer 3

• Anonymous volume
• Named volume
• Bind Volume
• Tmpf Volume

Question 4

By default, Docker uses what kind of volume?

Answer 4

Anonymous volume

Question 5

What are the 2 ways we can create a new volume?

Answer 5

1. docker-compose.yml file

2. Docker Desktop app

Question 6

How do we create a volume in the docker-compose.yml file?

Answer 6

Need:

• Volumes section
• Declare name of new volume

Question 7

How do we create a volume in Docker Desktop app?

Answer 7

1. Click ‘New Volume’ button

2. Enter volume name

Question 8

Add the volume ‘my_volume’ to this docker-compose.yml file located at var/www/log

Answer 8

webserver:
     build: ./app1
     ports:
          - "80"
     volumes:
          - my_volume:/var/www/log

Question 9

Can the same volume be mounted on multiple containers?

Answer 9

Yes

Question 10

A file can only be written to ____ to avoid lockup/access issues

Answer 10

one container at a time

Question 11

A file can only be written to ____ to avoid lockup/access issues

Answer 11

one container at a time

Question 12

What are the 2 types of syntax you can use when declaring a volume?

Answer 12

1. Short syntax

2. Long syntax

Question 13

What is short syntax?

Give an example

Answer 13

volumes:

- new_volume:/var/www/log

Question 14

What is long syntax?

Give an example

Answer 14

volumes:

 - type: volume
   source: my_new_volume
   target: /var/www/log

Question 15

What is long syntax?

Give an example

Answer 15

volumes:

 - type: volume
   source: my_new_volume
   target: /var/www/log

Question 16

What can you use for the source in short syntax?

Answer 16

• Name

- Path

Question 17

What can you use for the source in long syntax?

Answer 17

• Name

Question 18

What can you use for the source in long syntax?

Answer 18

• Name

Question 19

What is are Bind Volumes?

Answer 19

Binds a local folder on the host to the container

Question 20

What is a pro to using Bind Volumes?

Answer 20

Allows easy access on the host

Question 21

What is a con to using Bind Volumes?

Answer 21

Risky when deploying between hosts as permissions may not work

Question 22

How can you make a volume read-only?

Why might you do this?

Answer 22

volumes:
     - type: volume
       source: my_new_volume
       target: /var/www/log
       read_only: true

You can config files that containers need by shouldn’t modify

Question 23

How can you make a volume nocopy?

Why might you do this?

Answer 23

volumes:
     - type: volume
       source: my_new_volume
       target: /var/www/log
       volume:
           nocopy: true

Good if you have a shared volume but you want it to occupy a space that would have had others files in it already

Question 24

Which type of volume doesn’t use the source command?

Answer 24

Tmpf Volumes

Question 25

Why might you use tmpf?

Answer 25

If youre working with sensitive data

You want to limit size

Question 26

Declare a tmpf volume with max size of 100B

Answer 26

volumes:

 - type: tmpfs
   target: /var/www/log
   tmpfs:  
        size: 100B

Question 27

What is the peculiarity of using tmpfs on the WSL (Windows Subsystem for Linux)?

Answer 27

• Doesnt support tmpfs
• Writes to a file instead of memory, which isn’t cleared when the container is killed
• Doesnt respect the size command

Question 28

What is the peculiarity of using tmpfs on the WSL (Windows Subsystem for Linux)?

Answer 28

• Doesnt support tmpfs
• Writes to a file instead of memory, which isn’t cleared when the container is killed
• Doesnt respect the size command

Question 29

What type of volume would never have files be copied from the underlying container into the volume during setup? Why?

Answer 29

Bound Volumes

Security issue: Files could be copied anywhere on the host, meaning file can end up somewhere it shouldn’t