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Volume management

Learn to manage volumes with docker volume ls and rm.

Volume management

The docker volume subcommands:

docker volume ls                 # list
docker volume inspect pgdata     # details: Mountpoint, creation
docker volume rm pgdata          # delete (no container must use it)
docker volume prune              # delete anonymous volumes no container uses
docker volume prune -a           # also the unused named ones

Deleting a volume can't be undone; take a backup first for database volumes.

Backing up a volume

The standard way to back up a volume is to mount it and a host folder into a temporary container and create a tar archive:

docker run --rm -v pgdata:/veri:ro -v "$PWD":/yedek alpine \
  tar czf /yedek/pgdata.tar.gz -C /veri .

# restoring
docker run --rm -v pgdata:/veri -v "$PWD":/yedek alpine \
  tar xzf /yedek/pgdata.tar.gz -C /veri

Copying a running database's files can be inconsistent; the database should also be backed up with its own tools (pg_dump).

Practice A volume backup

Write two commands: list the volumes; then in an alpine container deleted when done, mount pgdata read-only at /veri and the current folder ("$PWD") at /yedek, and run tar czf /yedek/pgdata.tar.gz -C /veri .

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker volume ls
docker run --rm -v pgdata:/veri:ro -v "$PWD":/yedek alpine tar czf /yedek/pgdata.tar.gz -C /veri .

Expected output

DRIVER    VOLUME NAME
local     pgdata
local     redisdata

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 After docker rm -f db, what happens to the pgdata volume db had mounted?

  • It is added to the image
  • It gets corrupted
  • It stays; it must be deleted separately Correct answer
  • It is deleted automatically

Explanation: docker rm -v only deletes anonymous volumes along with it.

2 Show the volume's details.

Question 
docker volume ____ pgdata
Answer 
docker volume inspect pgdata

Explanation: inspect gives information like the Mountpoint as JSON.

3 Match.

Term Meaning
volume ls List
volume inspect Details
volume rm Delete
tar czf Backup archive

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project