What is Docker Volume? | DevOps Dictionary

Docker Volume — Persistent Storage That Outlives Containers

What Is a Docker Volume in Simple Terms?

Everything written inside a container is lost when the container is removed. A Docker volume is storage that lives outside the container — managed by Docker, stored on the host filesystem, and attached to the container at a specific path. The container can read and write to it normally, but the data persists even after the container is deleted.

Bash

Without volume:
  Container runs, writes data to /app/data
  docker rm container
  Data is GONE permanently
 
With volume:
  Container runs, writes data to /app/data
  /app/data is mounted from volume postgres-data
  docker rm container
  Volume postgres-data still exists with all data
  New container mounts same volume
  Data is still there

Volume vs Bind Mount vs tmpfs

Bash

Docker Volume (recommended for production data):
  -v postgres-data:/var/lib/postgresql/data
  Stored at: /var/lib/docker/volumes/postgres-data/_data
  Managed by Docker
  Survives container removal
  Portable between containers
 
Bind Mount (for development):
  -v /host/path:/container/path
  Uses actual host filesystem path
  Changes on host appear in container immediately
  Good for: code hot-reload, config injection
 
tmpfs (for temporary sensitive data):
  --tmpfs /tmp
  In-memory only — fastest I/O
  Lost when container stops
  Good for: secrets, caches that should not persist

Working With Volumes

Bash

# Create a named volume
docker volume create postgres-data
 
# Use in docker run
docker run -d \
  --name postgres \
  -v postgres-data:/var/lib/postgresql/data \
  -e POSTGRES_PASSWORD=secret \
  postgres:15
 
# List volumes
docker volume ls
# DRIVER    VOLUME NAME
# local     postgres-data
 
# Inspect — find where data is stored on host
docker volume inspect postgres-data
# "Mountpoint": "/var/lib/docker/volumes/postgres-data/_data"
 
# Remove a volume (permanent data deletion)
docker volume rm postgres-data
# Error if a container is using it
 
# Remove all unused volumes
docker volume prune
# WARNING: deletes volumes not used by any container
 
# In Docker Compose
services:
  postgres:
    volumes:
      * postgres-data:/var/lib/postgresql/data
 
volumes:
  postgres-data:    # top-level declaration — Docker manages it

Backing Up and Restoring Volumes

Bash

# Backup to tar file
docker run --rm \
  -v postgres-data:/source:ro \
  -v $(pwd):/backup \
  alpine \
  tar czf /backup/postgres-backup.tar.gz -C /source .
 
# Restore from tar file
docker volume create postgres-data-restored
docker run --rm \
  -v postgres-data-restored:/target \
  -v $(pwd):/backup:ro \
  alpine \
  tar xzf /backup/postgres-backup.tar.gz -C /target

PLACEMENT PRO TIP
**Tip:** Named volumes are the right choice for any data that must persist. Anonymous volumes (created without a name: `-v /var/lib/postgresql/data`) also persist but are hard to manage — they get random IDs and are difficult to back up or migrate. Always name your volumes.

COMMON MISTAKE / WARNING
**Common Mistake:** Storing database data in the container's own filesystem instead of a volume. The container filesystem uses OverlayFS which is slower for database I/O and is deleted with the container. Always use `-v named-volume:/db/data/path` for any database container.