How to

Install Docker Community Edition ( DockerCE )

sudo apt remove docker docker-engine docker.io containerd runc ; \
sudo apt install ca-certificates curl gnupg lsb-release ; \
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

sudo apt update ; \ 
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin


sudo groupadd docker ; \
sudo usermod -aG docker $USER ; \
newgrp docker

# Optional
sudo chown "$USER":"$USER" /home/"$USER"/.docker -R ; \
sudo chmod g+rwx "$HOME/.docker" -R


sudo systemctl enable docker.service ; \
sudo systemctl enable containerd.service

sudo gpasswd -a $USER docker

Uninstall Docker

sudo apt-get remove docker docker-engine docker.io containerd runc
sudo apt-get purge docker-ce docker-ce-cli containerd.io
sudo rm -rf /var/lib/docker

Remove all non-used docker containers

docker system prune

Removing "<none>" images

docker rmi $(docker images -f "dangling=true" -q)

Show real-time logs from the initialized container

docker logs -f container-name

Size of container

docker ps --size

Get running containers

Name

docker ps -f status=running --format "{{.Names}}"

JSON

docker ps -f status=running --format "{{json .}}"

Show online/offline containers

#!/bin/sh
list_of_containers="container1 container2container3"
containers=`docker ps -f status=running --format "{{.Names}}"`
for container in $list_of_containers
do
  if echo $containers |grep -q $container
    then  echo "$container online "
  else echo "$container offline"
    #exit 1
  fi
done
exit 0

Create temporary containers

docker run -it --rm --name my-frontend-build -v "$PWD":/home/node/app -w /home/node/app node:13-alpine sh -c "npm run build"

Docker Service Providers DNS

nmcli dev show | grep IP4.DNS

Specify DNS servers for Docker

sudo nano /etc/docker/daemon.json
  
  {
    "dns": ["8.8.8.8", "8.8.4.4"]
  }
  
 sudo service docker restart

Set Memory limit

Memory

For instance, let's limit the memory that the container can use to 512 megabytes. To constrain memory, we need to use the m parameter:

$ docker run -m 512m nginx

We can also set a soft limit called a reservation. It's activated when docker detects low memory on the host machine:

$ docker run -m 512m --memory-reservation=256m nginx

CPU

By default, access to the computing power of the host machine is unlimited. We can set the CPUs limit using the cpus parameter. For example, let's constrain our container to use at most two CPUs:

$ docker run --cpus=2 nginx

We can also specify the priority of CPU allocation. The default is 1024, higher numbers are higher priority:

$ docker run --cpus=2 --cpu-shares=2000 nginx

Similar to the memory reservation, CPU shares play the main role when computing power is scarce and needs to be divided between competing processes.

Setting Memory Limit With the docker-compose File

We can achieve similar results using docker-compose files. Mind that the format and possibilities will vary between versions of docker-compose.

Versions 3 and Newer With docker swarm

Let's give the Nginx service limit of half of CPU and 512 megabytes of memory, and reservation of a quarter of CPU and 128 megabytes of memory. We need to create “deploy” and then “resources” segments in our service configuration:

services:
  service:
    image: nginx
    deploy:
        resources:
            limits:
              cpus: 0.50
              memory: 512M
            reservations:
              cpus: 0.25
              memory: 128M

To take advantage of the deploy segment in a docker-compose file, we need to use the docker stack command. To deploy a stack to the swarm, we run the deploy command:

$ docker stack deploy --compose-file docker-compose.yml bael_stack

Version 2 With docker-compose

In older versions of docker-compose, we can put resource limits on the same level as the service's main properties. They also have slightly different naming:

service:
  image: nginx
  mem_limit: 512m
  mem_reservation: 128M
  cpus: 0.5
  ports:
    - "80:80"

To create configured containers, we need to run the docker-compose command:

$ docker-compose up

Verifying Resources Usage

After we set the limits, we can verify them using the docker stats command:

$ docker stats
CONTAINER ID        NAME                                             CPU %               MEM USAGE / LIMIT   MEM %               NET I/O             BLOCK I/O           PIDS
8ad2f2c17078        bael_stack_service.1.jz2ks49finy61kiq1r12da73k   0.00%               2.578MiB / 512MiB   0.50%               936B / 0B           0B / 0B             2

MACOS

Set Bridge IP (docker bip)

cd ~/Library/Containers/com.docker.docker/Data/database/com.docker.driver.amd64-linux
echo '{"experimental": false,"debug":"true","bip":"172.18.19.1/24"}' > etc/docker/daemon.js

How to change the Docker default subnet IP address

If the Docker Engine default bridge network is conflicting with your internal network hosts access, you can change the default Docker subnet by following these steps:

1. First, you need to delete your old containers

   sudo docker-compose stop

2. Next, change the subnet IP inside "/etc/docker/daemon.json", by using this command:

   sudo vim /etc/docker/daemon.json

3. Type in the Netmask IP. With the following structure. Please keep in mind that the IP used here is an example:

   {
     "default-address-pools": [
       {"base":"10.10.0.0/16","size":24}
     ]
   }

4. Restart the Docker Daemon by using this command:

   sudo service docker restart

5. Create a new VSS container and postgres with the following command:

   sudo docker-compose up -d

And that’s it!

Docker unable to access from VPN

Linux

• Check your subnet IP here

• Reset your networks to set correct subnet ip

docker network prune

Using Docker Compose + OpenVPN

Set the content below inside your docker-compose file:

networks:
  default:
    driver: bridge
    ipam:
      config:
        - subnet: 10.10.1.0/24

Windows

• Set a "default-address-pool"

• Set a subnet network inside the docker-compose file