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Troubleshooting Docker and Kubernetes Containers

Summary: Fixing Common Issues with Docker

Explore methods to troubleshoot common Docker problems including Compose orchestration, accessing files in images, handling YAML and package errors, reviewing container exit codes, and managing volume mounts for persistent data. This lesson equips you to efficiently debug Docker environments.

We'll cover the following...

Docker Compose overview

We introduced what Docker Compose is. We defined Docker Compose as an orchestrator for running multiple containers using a YAML script for configuring services. We stated that Docker Compose uses a declarative concept for defining services, i.e., we define the desired state of our application, and it gives us just that. We explained that the Docker Compose YAML script consists of multiple sections like version, services, networks, and volumes. Here’s how a Docker Compose file is structured:

YAML
version: '3'
services:
  apache:
    image: httpd:latest
    ports:
      - 80:80
    volumes:
      - ./httpd.conf:/usr/local/apache2/conf/httpd.conf
      - ./html:/usr/local/apache2/htdocs
    command: ["sh", "-c", "tail -f /dev/null"]
    stdin_open: true
    tty: true
  redis:
    image: redis:latest
    ports:
      - 6379:6379
networks:
  frontend:
  backend:

We used Docker CLI commands, some of which can be seen below.

Shell
# This command creates and starts containers defined in the Docker Compose file
docker-compose up -d
# This command gives us a list of services running in our Docker Compose file
docker-compose ps

Accessing files in an image

We look at reasons why files should be accessed or read in an image. Some of the reasons are:

  • Security

  • Debugging

  • Verifying build process

  • Inspecting contents

  • Extracting data

We discussed what to note when accessing files in an image:

  • Image layers

  • File permissions

  • Volumes

We concluded the lesson by accessing files in an image by spinning a ...