Docker Tmpfs Mounts

A tmpfs mount stores data in host memory, not on disk.

Syntax

# Mount tmpfs
docker run -d --tmpfs /app/temp myapp

# With options
docker run -d --tmpfs /app/temp:rw,size=100m,noexec myapp

Tmpfs Options

# Read-write
docker run -d --tmpfs /app/temp:rw myapp

# Size limit
docker run -d --tmpfs /app/temp:size=100m myapp

# No execute
docker run -d --tmpfs /app/temp:noexec myapp

# No suid
docker run -d --tmpfs /app/temp:nosuid myapp

# Combined
docker run -d --tmpfs /app/temp:rw,size=100m,noexec,nosuid myapp

Use Case: Temp Files

# Store temporary files in memory
docker run -d \
  --name app \
  --tmpfs /app/temp:rw,size=50m \
  --tmpfs /app/cache:rw,size=100m \
  myapp

Use Case: Application

version: '3.8'

services:
  api:
    build: ./backend
    tmpfs:
      - /app/temp:rw,size=50m
      - /app/cache:rw,size=100m

  worker:
    build: ./worker
    tmpfs:
      - /tmp:rw,size=200m

Storage Comparison

Everyday Use Case

Case: The application requires temp files.

# Run with tmpfs
docker run -d \
  --name app \
  --tmpfs /app/temp:rw,size=100m \
  myapp

# Data in /app/temp is stored in memory
# It is lost when the container restarts

Best Practices

1. Use for temp files: Not for important data
2. Set a size limit: Avoid excessive memory usage
3. Use noexec: For security
4. Consider alternatives: A volume or bind mount may be better

Troubleshooting

Tmpfs not available

# Make sure you are using Docker 17.06+
docker --version

# Check the mount
docker inspect container_name | grep Tmpfs

Conclusion

Tmpfs mounts are useful for temporary files that require high performance. Use them for cache or temp files, not for important data.