Day 1: Install Docker & Practice Container Commands

Install Docker

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
sudo yum install -y docker-ce docker-ce-cli containerd.io
sudo systemctl enable --now docker

Add user to docker group

sudo usermod -aG docker $USER

Test docker

docker run hello-world

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Run Docker with IPv4 only

Create file:

/etc/docker/daemon.json

Add configuration:

{
 "ipv6": false,
 "dns": ["8.8.8.8","1.1.1.1"]
}

Restart docker

systemctl restart docker

Verify

docker run hello-world

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Docker Basics

Pull Images

docker pull nginx
docker pull ubuntu
docker pull mysql

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Run Container

docker run -d --name mynginx -p 8080:80 nginx

Explanation

-d = run in background
--name mynginx = container name
-p 8080:80 = map container port 80 to host port 8080

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Enter Container

docker exec -it mynginx bash

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Stop / Start Containers

docker stop mynginx
docker start mynginx
docker restart mynginx

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View Logs

docker logs mynginx
docker logs -f mynginx

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Remove Containers

docker stop mynginx
docker rm mynginx

Remove all stopped containers

docker container prune

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Port Mapping Example

docker run -d --name mynginx -p 8081:80 nginx

Container port 80 → Host port 8081

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Volumes (Persistent Data)

Create configuration file

mkdir -p /data/docker
touch /data/docker/my.cnf

chown 999:999 /data/docker/my.cnf
chmod 644 /data/docker/my.cnf

Run MySQL container

docker run -d \
--name mydb \
-e MYSQL_ROOT_PASSWORD=pass123 \
-v /data/mysql:/var/lib/mysql \
-v /data/docker/my.cnf:/etc/mysql/conf.d/my.cnf \
-p 3306:3306 \
mysql:latest

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Build Your Own Docker Image

Create Dockerfile

cat > Dockerfile <<EOF
FROM mysql:8.0

LABEL maintainer="you@example.com"

COPY my.cnf /etc/mysql/conf.d/my.cnf

RUN apt-get update && apt-get install -y \
    vim \
    net-tools \
 && apt-get clean
EOF

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Useful Docker Commands

docker images        # list images
docker ps            # list containers
docker stats         # container resource usage
docker logs -f name  # view logs
docker inspect name  # container config
docker exec -it name bash  # enter container
docker top name      # processes inside container
docker system df     # disk usage

---

Run Container With CPU & Memory Limits

docker run -d \
--name mydb5 \
-e MYSQL_ROOT_PASSWORD=pass123 \
-p 3308:3306 \
--memory="1g" \
--cpus="1.5" \
mysql:8.0

Verify limits

docker inspect mydb5 | grep -i -E "memory|cpus"

Live resource usage

docker stats mydb5

Check inside container

docker exec -it mydb5 cat /sys/fs/cgroup/memory/memory.limit_in_bytes
docker exec -it mydb5 cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us
docker exec -it mydb5 cat /sys/fs/cgroup/cpu/cpu.cfs_period_us

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Restart Policies

docker run -d \
--name mydb10 \
--restart=always \
-e MYSQL_ROOT_PASSWORD=pass123 \
-p 3310:3306 \
mysql:latest

Restart options

no
on-failure
always
unless-stopped

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Docker Networking

Default network: bridge

Create network

docker network create mynet2
docker network inspect mynet2

Run container on network

docker run -d \
--name mydb12 \
--restart=always \
-e MYSQL_ROOT_PASSWORD=pass123 \
-p 3312:3306 \
--network mynet2 \
mysql:latest

Connect container to multiple networks

docker network connect mynet mydb9
docker network connect mynet1 mydb9
docker network connect mynet2 mydb9
docker network connect mynet3 mydb9

Network types

bridge   : containers on same host
host     : use host network
none     : isolated container
overlay  : multi-host cluster networking

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Docker Health Checks

Example

docker run -d \
--name web2 \
--restart unless-stopped \
--health-cmd="curl -f http://localhost:80 || exit 1" \
--health-interval=30s \
--health-retries=3 \
--health-timeout=5s \
nginx

Exit codes

0 = success
1 = failure
command missing = failure

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Copy Files From Container

docker cp temp-tomcat:/usr/local/tomcat/conf /data/mytomcat

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Production MySQL Container Example

docker run -d \
--name mydb16v8 \
-e MYSQL_ROOT_PASSWORD=pass123 \
-e TZ="Asia/Kolkata" \
--restart unless-stopped \
--health-cmd="mysqladmin ping -h localhost -u root --password=pass123 || exit 1" \
--health-interval=5s \
--health-retries=5 \
-v /data/mysql16v8:/var/lib/mysql \
-v /data/docker/my.cnf:/etc/mysql/conf.d/my.cnf \
-p 3316:3306 \
--memory="1g" \
--cpus="1.5" \
--network mynet2 \
my-mysql-image:8.0

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Deploy Tomcat With WAR

docker run -d \
--name tomcat3 \
--restart unless-stopped \
--health-cmd="curl -f http://localhost:8080 || exit 1" \
--health-interval=30s \
--health-retries=3 \
--health-timeout=5s \
-e TZ="Asia/Kolkata" \
-e JAVA_OPTS="-Xms128m -Xmx256m -Duser.timezone=Asia/Kolkata" \
-p 8083:8080 \
--network mynet2 \
-v /data/tomcat_docker/tomcat_common/warfile/log-api-1.0.war:/usr/local/tomcat/webapps/log-api-1.0.war \
-v /data/tomcat_docker/tomcat3/logs:/usr/local/tomcat/logs \
-v /data/tomcat_docker/tomcat_common/db_properties/db.properties:/usr/local/tomcat/conf/db.properties \
tomcat:9.0.111-jdk8-corretto-al2

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Nginx Load Balancer Container

docker run -d \
--name nginxlb \
--restart unless-stopped \
--network mynet2 \
-p 80:80 \
-p 443:443 \
-v /data/nginx-lb/nginx.conf:/etc/nginx/nginx.conf:ro \
-v /data/nginx-lb/SSL:/etc/nginx/SSL:ro \
-v /data/nginx-lb/logs:/var/log/nginx \
--health-cmd="sh -c 'echo > /dev/tcp/127.0.0.1/80 || exit 1'" \
--health-interval=30s \
--health-retries=3 \
--health-timeout=5s \
-e TZ="Asia/Kolkata" \
nginx:stable

Test request

curl -k "https://localhost:443/log-api-1.0/log?msgtext=thisistest4011116&status=ok"

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Docker Compose Basics

Start containers

docker compose up -d

Stop containers

docker compose down

Rebuild containers

docker compose up -d --build

Force recreate

docker compose up -d --force-recreate