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Docker Notes For Fresh Learner

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centos-install.md
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# Docker Notes - Best Practices

## Table Content
```
1. Docker Architecture
3. Cheat Sheet
4. Docker CLI
4.1. List all docker image
4.2 Running ubuntu bash
4.3. List of containers
4.4. Docker commit
5. Running processes in container
5.1. View output of container
5.2. Kill a container
6. Manage container
6.1. Memory limits
6.2. CPU limits
7. Networking
7.1. Getting container ip
7.2. UDP ports
8. Connecting between Containers
8.1. host -> container
8.2. container --> container
9. container connects to other container directly.
10. Listing images
10.1. Getting images
10.2. Removing images
11. Volumes
11.1. Sharing data with the host
11.2. Sharing Data between Containers
12. Docker Registries
12.1. Finding Images
13. Dockerfile
14. References
```

## 1. Docker Architecture
![](http://apachebooster.com/kb/wp-content/uploads/2017/09/docker-architecture.png)

## 2. Setup
* [CentOS](centos-install.md)

## 3. Cheat Sheet

https://github.com/wsargent/docker-cheat-sheet#why-docker

![](http://extremeautomation.io/img/cheatsheets/cheat_sheet_docker_page_1.png)

## 4. Docker CLI

### 4.1. List all docker image
```
docker images
```
### 4.2 Running ubuntu bash
- image --> docker run --> running container --> stopped container --> docker commit --> new images
- image is not change.

#### -ti = terminal keyboardInteractive
```
docker run -ti ubuntu:latest
```
### 4.3. List of containers
```
docker ps
```
#### List of docker with format
```
docker ps --format $FORMAT
```
#### List all (-a)
```
docker ps -a
```
#### List last (-l)
```
docker ps -l
```
### 4.4. Docker commit
- create new image from container
```
docker commit <docker id | name> [<new-image-name>]
```
- set tag for new images
```
docker tag < sha256 > < tag-name >
```
ex:
```
docker tag 52caa40054059fc07e4148337efa0a937799dc25ddc6b2e9f4d7deec4cf63177 my-image
```
test:

```
docker run -ti my-image
```

## 5. Running processes in container

* --rm : do not keep container after finish process
```
docker run --rm -ti ubuntu sleep 5
docker run --rm -ti ubuntu cat /etc/hosts
docker run -ti ubuntu bash -c "sleep 5; echo done"
```
* -d : (detach) run docker process in background
```
docker run -d -ti ubuntu bash
```
* attach
```
docker ps -l [--format $FORMAT]
docker attach <container-name>
```
* detach, leave it running in background
Control P + Control Q

* add another process in existed container
```
docker exec -ti <container-name> <command>
```
ex:
```
docker exec -ti gifted_kirch bash
```

### 5.1. View output of container
```
docker logs <container-name>
```
ex:
```
docker run --name my-container -d ubuntu bash -c "more /etc/hosts"
docker logs my-container
```
### 5.2. Kill a container
```
docker kill <container-name>
```

## 6. Manage container
### 6.1. Memory limits
```
docker run --memory <maxium-allowed> <image-image> <command>
```
### 6.2. CPU limits
```
docker run --cpu-shares relative to other containers
docker run --cpu-quota to limit it in general
```
## 7. Networking

![](https://goldmann.pl/images/docker-network/network.png)

ex:
- echo-server ( -p port_in[:port_out] )
```
docker run --rm -ti -p 45678:45678 -p 45679:45679 --name echo-server ubuntu:14.04 bash

nc -lp 45678 | nc -lp 45679
```
### 7.1. Getting container ip
```
docker ps
docker inspect <container-id> | grep IP
```
```
nc <container-ip> <port>
```
ex1:
```
nc 172.17.0.2 45678
nc 172.17.0.2 45679
```
ex2:
```
docker run --rm -ti -p 45678 -p 45679 --name echo-server ubuntu:14.04 bash

docker port echo-server
```
### 7.2. UDP ports
```
docker run -p ousite-port:insite-port/protocol(tcp/udp)
```
ex:
```
docker run -p 1234:1234/udp
```
## 8. Connecting between Containers

Client Container-->Host Network--->Virtual Network ---> Server Container

ex:
```
docker run -ti --rm -p 1234:1234 unbuntu:14.04 bash
nc -lp 1234
```
### 8.1. host -> container
```
docker ps -l
docker inspect <container-id> | grep IP
nc <container-ip> 1234
```
### 8.2. container --> container
```
docker run -ti --rm ubuntu:14.04 bash
nc <container-id> 1234
```
## 9. container connects to other container directly.

- server
```
docker run -ti --rm --name server ubuntu:14.04 bash
nc -lp 1234
```
- client
```
docker run --rm -ti --link server --name client ubuntu:14.04 bash
nc server 1234
```
- Link directly:
+ A service with its DB - not good
+ Automatically assigns a hot name
+ That links can break when containers restart

### 9.1. Making Links Not Break

- Docker has private networks.
- Fix the Links
- Must create the networks in advance
```
docker network create <network-name>
```
ex:
* server
```
docker network create example
docker run --rm -ti --net=example --name server ubuntu:14.04 bash
nc
nc -lp 1234
```
* client
```
docker run --rm -ti --link server --net=example --name client ubuntu:14.04 bash
nc server 1234
```
- Now kill the server and restart again.
- The link between server and client does not break.

### 9.2. Limiting access to only host

```
docker run -p 127.0.0.1:1234:1234/tcp
```

## 10. Listing images
- List downloaded images
```
docker images
```
- Tagging gives images
```
docker commit <container-id|name> <new-image-name>[:<tag>]
```
ex:
```
docker ps -l
docker commit b5938fe91f4c my-image-now
docker images
```
### 10.1. Getting images
- for offline work
```
docker pull
```
### 10.2. Removing images
```
docker rmi <image-name|id>
```
ex:
```
docker images
docker rmi my-image
```

## 11. Volumes
- Sharing data between containers and containers and host.
- Virtual "dicsc"
- Two types:
  + Persistent : Keep when container went away.
  + Ephemeral: exists in container life.
- Volumes is not a part of image.

### 11.1. Sharing data with the host
- like VMware.
- Sharing folders with the host
ex:
```
mkdir /home/docker/my-volume
docker run -ti -v=/home/docker/my-volume:/shared-folder ubuntu bash
cd /shared-folder
touch my-data
Press Crtl + D

ls ./my-volume/shared-folder
```
- Sharing a "single file" into a container

### 11.2. Sharing Data between Containers
* volumes-from
* Shared disks that exist only as long as they are being used
* Can be shared between containers

ex
- Container #1
```
docker run -ti -v /shared-data ubuntu bash
echo "hello, is it great!" > /shared-data/my-file
```
- Container #2
```
docker ps -l
docker run -ti --volumnes-from jovial_goodall ubuntu bash
cat /shared-data/my-file
```

## 12. Docker Registries

- Registries and distributes images.

### 12.1. Finding Images

https://hub.docker.com

```
docker search centos
```

- Push image to the world.
```
docker login
docker pull centos
docker tag centos:123 test/test-image-32:v123.1234
docker push test/test-image-32:v123.1234
```
Note: Do not push password with the image

## 13. Dockerfile
- What is it ?
+ code to create image

docker build -t name-of-result .

+ each line takes the image of previous line and makes another images.
+ the previous image is unchanged.

## 14. References
1. https://docs.docker.com/engine/reference/builder/
2. http://apachebooster.com/kb/wp-content/uploads/2017/09/docker-architecture.png
3. https://github.com/wsargent/docker-cheat-sheet#why-docker
4. http://extremeautomation.io/img/cheatsheets/cheat_sheet_docker_page_1.png

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