Master Docker Persistence, Networking, and Resource Limits with Practical Examples

Docker Data Persistence

Docker provides three mechanisms to mount host data into a container:

Volumes : Managed by Docker under /var/lib/docker/volumes. Recommended for persistent data.

Bind mounts : Directly mount any host directory or file.

tmpfs : Stores data in host memory only; no writes to the host filesystem.

Creating and Using a Volume

docker volume create nginx_vol   # create a Docker‑managed volume
ls /var/lib/docker/volumes/nginx_vol/

docker run -d --name nginx-ceshi -p 888:80 \
  --mount source=nginx_vol,destination=/usr/share/nginx/html nginx
# short syntax
# docker run -d --name nginx-ceshi -p 888:80 -v nginx_vol:/usr/share/nginx/html nginx

docker inspect nginx-ceshi

After the container starts, the persisted files are located at /var/lib/docker/volumes/nginx_vol/_data. Adding a file demonstrates persistence:

cd /var/lib/docker/volumes/nginx_vol/_data
 echo "hello world nginx" > index.html
# Access http://HOST_IP:888/ to verify

Bind Mount Example

docker run -d --name nginx-test \
  --mount type=bind,src=/app/wwwroot,dst=/usr/share/nginx/html nginx
# equivalent short form
# docker run -d --name nginx-test -v /app/wwwroot:/usr/share/nginx/html nginx

Key points:

Using -v with an absolute host path triggers bind mode; a plain name triggers volume mode.

The source path must exist; otherwise the container fails to start.

If the container’s target directory is non‑empty, it is hidden by the mount.

Docker Network Modes

Bridge (default)

Docker creates a docker0 bridge; containers join this network unless another mode is specified.

Host

The container shares the host’s network namespace, using the host’s interfaces directly.

None

The container gets an isolated network namespace with no automatic configuration; manual setup is required.

Container

Shares the network namespace of another container:

docker run -d --name zd -p 99:80 busybox
docker run -d --name nginx-zd --net container:zd nginx
# nginx now uses zd’s network stack

Custom Networks

Like the bridge driver but with built‑in DNS discovery, allowing containers to reach each other by name.

docker network create zf-100

Docker Resource Limits

Limiting resources prevents a container from exhausting host capacity and adds isolation. -m, --memory: Maximum memory usage (e.g., 500m). --memory-swap: Total memory + swap allowed. --oom-kill-disable: Disable the OOM killer. --cpus: Number of CPU cores (e.g., 1 or .5). --cpuset-cpus: Specific CPU cores (e.g., 0-3). --cpu-shares: Relative CPU weight.

Memory Limit Example

docker run -d --name web03 \
  --memory="500m" --memory-swap="600m" \
  --oom-kill-disable nginx
# Verify limits
docker stats --no-stream web03

CPU Limit Examples

# Limit to one CPU
docker run -d --name web01 --cpus="1" nginx
# Limit to 50% of a CPU
docker run -d --name web01 --cpus=".5" nginx