Network and Volume Commands

Commands for creating, inspecting, and troubleshooting Docker networks and volumes.

Network Commands

Listing and Inspecting

# List all networks
docker network ls

# Detailed network info (shows connected containers)
docker network inspect my-network

# List networks with filters
docker network ls --filter driver=bridge
docker network ls --filter scope=local

Creating Networks

# Create a bridge network
docker network create app-net

# Create with subnet
docker network create --subnet=172.20.0.0/16 app-net

# Create internal-only network (no internet access)
docker network create --internal backend

# Create with labels
docker network create --label project=myapp app-net

Connecting and Disconnecting

# Connect a running container to a network
docker network connect app-net my-container

# Connect with alias (additional DNS name)
docker network connect --alias api-service app-net my-container

# Disconnect from a network
docker network disconnect app-net my-container

Removing Networks

# Remove a specific network
docker network rm app-net

# Remove all unused networks
docker network prune

# Remove with force
docker network prune -f

Network Troubleshooting

DNS and Connectivity Testing

# Test DNS resolution from inside a container
docker exec -it my-app nslookup db
docker exec -it my-app ping -c 3 db

# Check which networks a container is on
docker inspect my-app --format '{{json .NetworkSettings.Networks}}'

# Check a container's IP address
docker inspect my-app --format '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}'

# Check port mappings
docker port my-app

# Detailed port mapping
docker inspect my-app --format '{{json .NetworkSettings.Ports}}'

Use a Debug Container

When your container does not have networking tools:

# Launch a debug container on the same network
docker run --rm -it --network app-net nicolaka/netshoot

# Inside netshoot:
nslookup db
curl http://api:8080/health
dig api

Troubleshooting Quick Reference

Symptom	Check Command
Container can't resolve service name	docker exec CONTAINER nslookup SERVICENAME
Containers can't communicate	docker inspect CONTAINER --format '{{json .NetworkSettings.Networks}}'
Port not accessible from host	docker port CONTAINER
Need full network topology	docker network inspect NETWORK
Need all published ports	docker ps --format 'table {{.Names}}\t{{.Ports}}'

Volume Commands

Listing and Inspecting

# List all volumes
docker volume ls

# List with filters
docker volume ls -f dangling=true    # Unused volumes
docker volume ls -f driver=local

# Detailed volume info (mount point, labels, created date)
docker volume inspect my-data

# Check which volumes a container uses
docker inspect my-app --format '{{json .Mounts}}'

Creating Volumes

# Create a named volume
docker volume create app-data

# Create with labels
docker volume create --label project=myapp --label env=prod app-data

Using Volumes

# Named volume mount
docker run -d -v app-data:/var/lib/data my-app:1.0.0

# Bind mount (host directory)
docker run -d -v /host/path:/container/path my-app:1.0.0

# Read-only mount
docker run -d -v app-data:/data:ro my-app:1.0.0

# Tmpfs mount (in-memory, no persistence)
docker run -d --tmpfs /tmp my-app:1.0.0

Backup and Restore

# Backup a volume to a tar file
docker run --rm -v app-data:/source -v $(pwd):/backup alpine \
  tar czf /backup/app-data-backup.tar.gz -C /source .

# Restore from backup
docker run --rm -v app-data:/target -v $(pwd):/backup alpine \
  tar xzf /backup/app-data-backup.tar.gz -C /target

# Database-specific backup (PostgreSQL example)
docker exec my-postgres pg_dump -U postgres mydb > backup.sql

# Database restore
docker exec -i my-postgres psql -U postgres mydb < backup.sql

Removing Volumes

# Remove a specific volume
docker volume rm app-data

# Remove all unused volumes
docker volume prune

# Force remove
docker volume prune -f

Volume Prune Warning

docker volume prune deletes all volumes not attached to a running container. If your database container is stopped, its data volume will be deleted.

Mount Types Comparison

Type	Syntax	Persistence	Use Case
Named volume	-v vol_name:/path	Persistent, Docker-managed	Database data, app state
Bind mount	-v /host:/container	Persistent, host-managed	Dev hot-reload, config files
Read-only mount	-v vol:/path:ro	Read-only access	Config, certificates
Tmpfs	--tmpfs /path	In-memory, ephemeral	Temp files, caches, secrets

Combined Quick Reference

Goal	Command
List networks	docker network ls
Create network	docker network create NAME
Inspect network	docker network inspect NAME
Join container to network	docker network connect NET CONTAINER
Remove unused networks	docker network prune
Container's network membership	docker inspect CONTAINER --format '{{json .NetworkSettings.Networks}}'
Container's IP address	docker inspect CONTAINER --format '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}'
Port mappings	docker port CONTAINER
List volumes	docker volume ls
Create volume	docker volume create NAME
Inspect volume	docker volume inspect NAME
Check dangling volumes	docker volume ls -f dangling=true
Container's mounts	docker inspect CONTAINER --format '{{json .Mounts}}'
Backup volume	docker run --rm -v VOL:/src -v $(pwd):/bak alpine tar czf /bak/backup.tar.gz -C /src .
Remove volume	docker volume rm NAME
Remove unused volumes	docker volume prune (⚠ data loss)
DNS test	docker exec -it CONTAINER nslookup SERVICE

What's Next

• Continue to Compose Commands.