Docker tutorial for beginners

Docker is a containerized way of running different application with the same or different packages, tooks, source code without affecting one another in a same pc, instance or hypervisor. The docker run time will be the same for all of these docker images provided they are running on the same pc.

Docker basics

Running the docker image

This is the first way to run a docker image

docker run -p <pc_port>:<docker_port> <docker_image_name>
docker run --publish <pc_port>:<docker_port> <docker_image_name>

The image above will stop if you click ctrl + c on your pc

if you want to run a docker image in the background without interuption use the following command

docker run -p -d <pc_port>:<docker_port> <docker_image_name>
docker run --publish --detach <pc_port>:<docker_port> <docker_image_name>

Note that -p = --publish and -d = --detach

Examples are given below

1. Running a docker-nginx image

docker run -p -d 8000:80 nginx

2. Running an apache web server

docker run -p -d 8000:80 apache
# could be wrong

3. Running custom images

# will add more notes on this one

List running containers

If you want to see all containers running in your pc use the following commands

dcoker containers ls # returns running containers
dcoker ls
dcoker ls -a
docker ps # this is an old way of doing it but it still works

-a means all or irrespective of their status

To stop a container

if you a container is running in the image and you want to stop it use

docker container stop <container-id>
docker stop <container-id>
docker container stop <container-name>
docker stop <container-name>
docker container stop <container-first-four-charectors-on-id>
docker stop <container-first-four-charectors-on-id>

Instances when a container is hidden

when an instance has been stopped it will be hidden to see it use docker ls -a

To search images on dockerhub

To search images on dockerhub

docker search <image-name>

To start existing images

This will start only existing stopped images

docker start <image-name or id>

To restart existing images

This will restart only existing stopped or running images

docker restart <image-name or id>

Defining a static container name

When running a container using docker run without providing a name for the container,dcker will create an assign a default name to that container of some famous scientists however if you want to assign a name for a container use '--name '

e.g

docker run -p -d 8000:80 --name <name-you-want> nginx
docker run -p -d 8000:80 --name web_server nginx

To see the result of this use

docker ps
docker ps -a

To see problems or logs on a container

docker logs <container name>

To see processes in a container

docker top <container-name> or < container-id>

also try this for all

ps -ef | grep <container-name>
ps -ef | grep nginx

To remove or delete a container

rm to running containers will give you an error

docker rm <container-id>
docker rm <container-id> <...id2> <id3>

Differences between Containers and Virtual Machines

1. They both have resource allocation and allocation benefits but the memory allocation for VMs is static where for containers it's static

2. Containers virtualizes operating systems where as VMs virtualizes hardware

3. Containers are more portable (1 creation multiple execution on different machines)

4. Containers are just processes

5. Contianers are limited to resources they can access

6. Containers can be killed on exit

Execute a container with user supplied arguments

docker run --name custom-mysql -e MYSQL_ROOT_PASSWORD=#Mulalo96 -d mysql

Docker Monitoring

Resource Consuption Stats

docker stats <container_name or container_id>

Get detail information about a container (running)

Get a detailed information about docker container when running

docker inspect <container_name or container_id>

Execute the container in interactive mode

docker run -it <image_name> <commands>

• using -i: means it will keep the stdin open if not attached
• using -t: Allow a pseudo-TTY terminal open

examples

docker run -it nginx /bin/bash # to access the terminal of the container
docker run -it nginx ls
docker run -it nginx pwd

this works when launching only

Execute the bash commands on container that is already created

docker exec -it <image-name or id> touch /tmp/carrie
docker exec -it <image-name or id> /bin/bash
# docker run -it --name mysql_name -e MYSQL_ROOT_PASSWORD=#Mulalo96 mysql -uroot -p
docker run -it --name mysql_client -e MYSQL_ROOT_PASSWORD=#Mulalo96 mysql

To stop all containers

docker stop $(docker ps -a -q)

To remove all containers

docker rm $(docker ps -a -q)
docker container prune # all stopped containers
docker image prune # not tagged latest

Useful commands for Docker

Before I leave you, I have prepared a list of commands that may be useful to you on Docker.

List your images.

docker image ls

Delete a specific image.

docker image rm [image name]

Delete all existing images.

docker image rm $(docker images -a -q)

List all existing containers (running and not running).

docker ps -a

Stop a specific container.

docker stop [container name]

Stop all running containers.

docker stop $(docker ps -a -q)

Delete a specific container (only if stopped).

docker rm [container name]

Delete all containers (only if stopped).

docker rm $(docker ps -a -q)

Display logs of a container.

docker logs [container name]

Docker networks

if you want to connect two instances/containers to run on the same network interface then this is the way.

Networks connects a container to another container and two containers to a host machine

Bridge Network

By default all docker containers are connected to the bridge network which is th default network created by the runtime envrionment. All containers in the bridge network communicate with each other using ip-addresses.Containers on different host machine cannot communicate with each other without additional configuration

Overlay Network

This model enables communication between containers from two or more different host machines. Technlogies like VXLAN or IPSec are often used to create virtual machines that span multiple hosts.

Container Network Interfaces

CNI is a specification that defines how a container runtime interacts with networking plugins. it allows different container runtimes to be combined with various networking solutions.

To find port of a container

docker port <contianer_id>
docker port <contianer_name>

Find docker container ip

docker inspect <contianer_id or name>

filter one item

docker inspect <container_id> -f {{ .key.value }}

Docker Network CLI Commands

1. to see all networks are available

docker network ls

2. to create a network

dcoker network create my_bridge_net

To filter networks

To filter networks in the bridge

docker network -f drive=bridge

To finds all networks ids and drivers

docker network ls -f "{{ .ID }}: {{ .Driver }}"

Try

docker network --help

Docker DNS (Domain Name System)

DNS is a system in which domains to thier respective ip addresses

Dontainers use DNS to communicate

can add network to container when run using --network <network_name>

check if containers in the same network are connected

docker run -it <container1> ping <container_2>