Containers & OpenShift (Docker & oc)

Practical runbook for daily Docker container management, resource inspection, and OpenShift image registry operations.

Docker Resource Inspection

System Disk Usage

Inspect how much disk space is consumed by images, containers, local volumes, and build caches:

docker system df

For verbose, per-item breakdown:

docker system df -v

Live Resource Utilization

Stream real-time CPU, memory, network I/O, and block I/O statistics across running containers:

docker stats

To format or stream specific containers:

docker stats --no-stream

Container Process Table

Display the running processes inside a specific container directly from the host:

docker top <container_id_or_name>

Host & Container File Transfer

Copy files or directories bidirectionally between a running container and the local filesystem:

# Copy from host to container
docker cp ./config.json <container_id>:/app/config.json

# Copy from container to host
docker cp <container_id>:/var/log/app.log ./app.log

OpenShift CLI (oc) Registry Workflows

When working with private OpenShift container registries, configure the local Docker daemon and authenticate using short-lived tokens.

1. Cluster Authentication

Log into the target OpenShift cluster via CLI:

oc login --server=<cluster-api-url> --token=<auth-token>

2. Insecure Registry Configuration

If the OpenShift internal image registry route uses self-signed or internal enterprise certificates, register the domain in Docker daemon’s configuration:

Edit /etc/docker/daemon.json (requires root privileges):

{
  "insecure-registries": [
    "default-route-openshift-image-registry.<cluster-domain>.com"
  ]
}

Reload and restart Docker:

sudo systemctl daemon-reload
sudo systemctl restart docker

3. Registry Authentication via CLI Token

Authenticate Docker directly against the OpenShift image registry using your active oc session token:

docker login -u openshift -p $(oc whoami -t) default-route-openshift-image-registry.<cluster-domain>.com

Reference Guides & Cheat Sheets