aladeeb / docker-learn

Docker

Docker notes.

---

Architecture

Docker Components:

• Images -> set of instructions to build the container configuration.
• Containers -> the running image.
• Registery -> like a repo.
• Client -> the CLI tool.
• Daemon -> takes the commands from the client and apply it on the runc.
• Namespaces -> isolate containers' resources from each other.

Docker Engine:

• Docker CLI
• REST API
• Docker Daemon

Running a container on a remote docker engine:

docker -H=remote-docker-engine-ip:2375 run -d nginx

---

Docker CLI

Commands:

• docker version: shows the details of docker components.
• docker info: gets an overview of the docker client/server.
• docker login: sets the dockerhub credentials to be able to pull/push from and to private repos.
• docker logout: logs out.

---

Images

Commands:

• docker build --tag imagename:version dockerfiledirectory: build a new image.
• docker images or docker image ls: list all the local images.
• docker pull imagename:version: pulls image from dockerhub.
• docker image inspect imagename: shows the details of the image.
• docker image rm imagename: removes the image locally.
• docker history imagename: gets the history/details of the image layers.
• docker tag sourceimage:!tag targetimage:!tag: create a tag target_image that refers to source_image.
• docker push imagename: push the image to the dockerhub.

Examples:

Saving an image as tar file.

docker save my-app:1.0 > my-app.tar

Loading an image from tar file.

docker load -i /home/ubuntu/my-app.tar

---

Containers

Commands:

• docker run [OPTIONS] imagename:version: runs a specific image from the local images, and if the image doesn't exist locally, it pulls it first from the dockerhub.
  • -d: runs the container in detached mode. -d equals --detach
  • -p port:port: defines the container with a specific port mapping. -p equals --publish
  • --name: defines the container name.
  • --restart: defines how the container will act in case of failure.
  • -v volumename/bindpath:destination: defines a friendly name for the volume.
  • --mount type=volume/bind/tmpfs,source=/data/myfolder,target=/var/lib/mysql: better option to add a volume or bind a directory.
  • -e: passing environment variables.
  • --cpus: allocates a specific cpu.
  • --memory: allocates a specific memory.
  • --network: defines the network of the container.
  • --link containername: links the container with another
• docker ps -all or docker container ls -all: list all the containers.
• docker stats containerid: gets the resources consumption for a specific container.
• docker container stop containerid: stops a container.
• docker container stop containerid: starts a container.
• docker container inspect --format='{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}': gets the IP of the container.
• docker logs containerid: gets the logs from the container.
• docker exec -it containerid command: runs interactive shell for a specific container. like docker exec -it containerid bash, opens a bash session.
• docker container rm containerid: removes the container, we can pass the first three letters of the container name.

---

Storage

there are different types of storage:

• Volumes
• Mount points
• tmpfs

Commands:

• docker volume ls: list all volumes.

Examples:

Attaching a volume while running a container

docker run -it -d -v myvolume:/mounted_folder alpine

---

Networking

types of networks:

• Bridge network: the default internal network for docker. Only containers inside the same network can see each other.
• Host: The host machine network, this is allowing containers to see each other.
• None: Isolation of the container, will not be published or even accessible by the other containers.
• Overlay
• Macvlan

Commands:

• docker network ls: list all networks.
• docker network inspect networkname: gets the details of the network and its attached containers.
• docker network create --driver drivername networkname: creates a network.
  • --subnet 172.120.0.0/16: defines the subnet of the network.
• docker network disconnect [OPTIONS] networkname containername: disconnects a container from the network.
• docker network connect [OPTIONS] networkname containername: connects a container from the network.

---

Docker Compose

Commands:

• docker compose build: rebuild the image/s if there's a change done on it.

---

Tips and Tricks

To stop all the running containers, use the below: (the same goes for the remove)

docker container stop $(docker container ps)

---

Popular Images:

• alpine -> lightweight linux image
• nginx -> webserver/proxy
• redis -> caching/in-memory database
• mariadb -> database
• timer -> prints timestamp every second---

---

Orchestration Tools:

• Docker Swarm
• Kubernetes
• Mesos
• Openshift