181 lines
6.1 KiB
Markdown
181 lines
6.1 KiB
Markdown
# Containerization with Docker
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## set up docker01 - Ubuntu 20.04 cloud server
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IP Address: 10.0.5.12 (change web01 address to 10.0.5.20) \
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Default Gateway: 10.0.5.2 \
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DNS: 10.0.5.5 \
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### changing hostname. it is different on Ubuntu Cloud
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- in `/etc/cloud/cloud.cfg`:
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```
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preserve_hostname: true
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hostname: docker01-charlotte (add this line under)
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fqdn: docker01-charlotte.charlotte.local (add this line under)
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```
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- change hostname for 127.0.1.1 in `/etc/hosts` file
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- finally, `sudo hostnamectl hostname docker01-charlotte`
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- update DNS records on mgmt01 (remember to change web01 record too)
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## docker installation
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https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-20-04
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update and install prerequisite packages, this will let apt use packages over HTTPS
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```
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sudo apt update
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sudo apt install apt-transport-https ca-certificates curl software-properties-common
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```
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add the GPG key
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```
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curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
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```
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add docker repo to APT sources
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```
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sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"
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```
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validate installation is from docker repo. Notice that docker-ce is not installed,
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but the candidate for installation is from the Docker repository for Ubuntu 20.04 (focal).
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```
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apt-cache policy docker-ce | head
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```
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install docker
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```
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sudo apt install docker-ce
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```
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check status
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```
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sudo systemctl status docker
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```
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### executing the docker command without sudo:
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add user to the docker group, apply the new group membership, and logout/log back in
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```
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sudo usermod -aG docker charlotte
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su - charlotte
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```
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## using docker
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### downloading images
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search for images availabe on Docker Hub
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```
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docker search <image-name>
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```
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download from Dockuer Hub
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```
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docker pull <image-name>
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```
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see installed images
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```
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docker images
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```
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## docker-compose
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- https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-compose-on-ubuntu-20-04
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> "Docker Compose is a tool that allows you to run multi-container application environments based on definitions set in a YAML file."
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download the 1.29.2 release and save the executable file at /usr/local/bin/docker-compose
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```
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sudo curl -L "https://github.com/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
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```
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make docker-compose executable:
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```
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sudo chmod +x /usr/local/bin/docker-compose
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```
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verify installation
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```
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docker-compose --version
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```
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The following command pulls down an Arch Linux based docker image, invokes it in a container, and runs /bin/echo "HELLO SYS265 SNOWY DAYS '' before deleting the container.
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```
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docker run --rm archlinux:latest /bin/echo "HELLO SYS265 SNOWY DAYS"
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```
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___
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## docker run command syntax (example)
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- e.g. The following command will pull down the image, application and dependencies associated with a simple python web application. `docker run -d -P training/webapp python app.py`
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- `docker`: CLI for interacting with docker
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- `run`: create and start a new container
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- `-d` (or `--detach`): the container runs in the background.
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- useful for non-interactive services, like webservers and databases
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- `-P` (or `--publich-all`): automatically publishes all exposed ports of the container to random host ports.
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- This allows external access to the services running in the container without having to specify port mappings manually.
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- `training/webapp`: the docker image from which the container is created
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- In this case, an image named `webapp` that is located in the `training` repository
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- `python`: command that will be executed inside the container once it starts
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- `app.py`: argument passed to the python command
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- the Python script `app.py` should be executed by the Python interpreter when the container starts.
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- `docker run httpd` will automatically set up an apache web server in the container
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### to stop docker process
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```
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docker stop <container ID>
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```
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## dockerized WordPress
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https://github.com/docker/awesome-compose/tree/master/wordpress-mysql
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- create a directory `docker-wp`
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- create compose.yml
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>[!Caution]
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> Absolutely never use a tab in a docker-compose.yml file
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```
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services:
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db:
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# We use a mariadb image which supports both amd64 & arm64 architecture
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image: mariadb:10.6.4-focal
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# If you really want to use MySQL, uncomment the following line
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#image: mysql:8.0.27
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command: '--default-authentication-plugin=mysql_native_password'
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volumes:
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- db_data:/var/lib/mysql
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restart: always
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environment:
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- MYSQL_ROOT_PASSWORD=somewordpress
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- MYSQL_DATABASE=wordpress
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- MYSQL_USER=wordpress
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- MYSQL_PASSWORD=wordpress
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expose:
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- 3306
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- 33060
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wordpress:
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image: wordpress:latest
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ports:
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- 80:80
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restart: always
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environment:
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- WORDPRESS_DB_HOST=db
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- WORDPRESS_DB_USER=wordpress
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- WORDPRESS_DB_PASSWORD=wordpress
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- WORDPRESS_DB_NAME=wordpress
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volumes:
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db_data:
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```
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- `docker compose up -d`
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- wait...it's really that easy?
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- yes
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___
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### showing how containers use the same kernel as the host
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- example: the following commands will:
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- Print out the current version of Ubuntu on docker01. `cat /etc/lsb-release`
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- Print out the current version of docker01's linux kernel. `echo "Current Kernel is: $(uname -a)"`
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- Invoke a container of the stored Ubuntu image as well as an interactive bash command prompt, and print out the kernel being used by the Ubuntu container. `docker run -it archlinux /bin/uname -a`
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- as you can see, both the docker container(archlinux) and the host(docker01-charlotte) are using the same kernels
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