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Docker-concepts-and-commands

concepts

Docker VS VM's

VMWare, VitualaBox

Has VM's that this vm's is complete vm's that has cernel and ultimate virtual infrastructure(Resources like ram,cpu,.. and cernel files)

Using hypervisor to interpretaion between vm's and HW/OS

Isolate

Load is high

Docker

Has containers that using needed os infrastructure and have not complete infrastracture(Resources like ram,cpu,.. and cernel files) itself

Has containers

Using docker engine

Scalable

Less complex

Easy to deploy

Docker

In docker images can be downloaded from docker hub or make images with Dockfile

Docker command lines and utilities

sudo docker pull <docker name>
sudo docker images

show running containers

sudo docker ps 

show all containers that were runned and exited

sudo docker ps -a
sudo docker run <docker name> if doesn't exist it pulls it
sudo docker run busybox [collection of common linux commands(ls, cat, sleep,...)] ------  > like sudo docker run busybox ls
sudo docker rm <CONTAINER ID> ---> delete contaiers that exited in <sudo docker ps -a>

Killed all containers (Than ones not running but were runned before)

sudo docker container prune
sudo docker rmi <image name> ---> remove image
sudo docker container prune ---> delete all contaiers that exited in <sudo docker ps -a>
sudo docker system prune --all --volumes --force ----> It's very important it's for deleting all storage occuped by docker in the above approached your storage doesn't chages

Automatically remove the container when it exits

sudo docker run --rm 
-i = --interactive:     Keep STDIN open even if not attached
-t = --tty:                  Allocate a pseudo-TTY
sudo docker run --rm -it busybox

When the above command is running you can use this command to run sum commad with busybox commands

sudo docker exec 9f14f56a57d1 touch /hi  ------> 
sudo docker exec -it f6ee306b43b7 bash (Go to the image running shell or connect to f6ee306b43b7(This is running redis container) by bash (This is like ssh))
sudo docker stop f6ee306b43b7 (stop running images)

If you want to set name to docker run and use it by ecex

sudo docker run --rm --name redis redis

Connect to above run image by its name

sudo docker exec -it redis bash
sudo docker exec -it redis bash redis-cli (run command line directly)

When you run a docker image on special port(e.i 6379 --> redis) you con connect it to your lacal's ip

sudo docker run --rm --name redis -p6379:6379 redis

When you run a docker image on special port(e.i 6379 --> redis) you con connect it to your lacal's ip and use redis your local (e.i use it in your flask app)

sudo docker run --rm --name redis -p6379:6379 redis

Persistence data

Above methods had a problem, that is when you disconnect your redis, its data removed and when you run it again you haven't previous data of redis.

To resolve this type of problem you should read image on docker hub and find "persistent storage" section that creator told us how to use his image to maintain data, for example in redis we have this command:

docker run --rm --name  redis -p6379:6379 redis redis-server --appendonly yes

When you run docker by above command after exitition of redis and go to bash you can see appendonly.aof is created in /data

But again we hava a problem that is data stored is in docker not in your local the solution is 'VOLUM' :

As you can see in this picture you can store piece of your stored data of docker in your local by -v or --mount(more information) this command connect your local /tmp/data/redis(your create it) to /data(from your redis conrainer):

docker run --rm --name  redis -p6379:6379 -v /tmp/data/redis:/data redis redis-server --appendonly yes

Now to run our app.py by docker we shoul use ubunto or Alpine (light linux), python, flask, nginx, wsgi(for connect nginx to our flask) dockers but a docker to this, its name is tiagolo/uwsgi-nginx-flask tiangolo :)

We create a Dockfile contain below content and build it with sudo docker build .:

# use this tiangolo image
FROM tiangolo/uwsgi-nginx-flask 
# Add flask requirements to run flask                                          
COPY ./requirements.txt /tmp/      
# By RUN you can run any linux commands
RUN pip install -r /tmp/requirements.txt  
                                                                                    
# Copy our app.py to app/main.py(from tiangolo docker image that tiangolo made it)
COPY app.py /app/main.py

To add name to your image you can use sudo docker build -t myapp:v1 .

As you can see in below picture we have two containers myapp and redis and two contaiers can be seen by OS but thay can't see each gether and now we want to connect them by create a network:

Using this command you can create a network

sudo docker network create flask
# You can see your network by
sudo docker network ls

Now you should run your dockers on this network like this

sudo docker run --rm --name  redis -p6379:6379 --network flask -v /tmp/data/redis:/data redis redis-server --appendonly yes
sudo docker run --rm -p80:80 --name myapp --network flask myapp:v3

But it doesn't work because two container connect to OS that it's not necessary anymore and dockers can see each other by container names.

# removing p6379:6379
docker run --rm --name  redis --network flask -v /tmp/data/redis:/data redis redis-server --appendonly yes
# Notic that we dont change p80:80 in our image

we should change our app to:

localhost ---> redis
r = redis.Redis(host='redis', port=6379, db=0)

And Done and you can run curl 0.0.0.0:80 and see your result also you can ping redis in your myapp bash like this:

sudo docker exec -it myapp bash
> ping redis

Docker-compose

Docker-compose is for managing containers.

By docker-compose we can use some different containers in one service

It's format is yml look at the sample --> docker-comose.yml

version: "3"

services: 
  app: 
    build: 
      context: .
    ports: 
      - "8000:8000"
    volumes: 
      - ./app:/app
    command: >
      sh -c "python manage.py runserver 0.0.0.0:8000"