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Docker Installation

4 min read

Has couple of ways, starting from the suggested

Default Way

Installing Docker is relatively straightforward. We can use the following script to install it on a Ubuntu host:

# Remove old docker installations
for pkg in docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc; do sudo apt-get remove $pkg; done
 
# Add Docker's official GPG key:
sudo apt-get update
sudo apt-get install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc
 
# Add the repository to Apt sources:
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "${UBUNTU_CODENAME:-$VERSION_CODENAME}") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
 
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Creating a Docker image is done by creating a Dockerfile, which contains all the instructions the Docker engine needs to create the container. We can use Docker containers as our “file hosting” server when transferring specific files to our target systems. Therefore, we must create a Dockerfile based on Ubuntu 22.04 with Apache and SSH server running. With this, we can use scp to transfer files to the docker image, and Apache allows us to host files and use tools like curl, wget, and others on the target system to download the required files. Such a Dockerfile could look like the following:

Dockerfile

# Use the latest Ubuntu 22.04 LTS as the base image
FROM ubuntu:22.04
 
# Update the package repository and install the required packages
RUN apt-get update && \
    apt-get install -y \
        apache2 \
        openssh-server \
        && \
    rm -rf /var/lib/apt/lists/*
 
# Create a new user called "student"
RUN useradd -m docker-user && \
    echo "docker-user:password" | chpasswd
 
# Give the htb-student user full access to the Apache and SSH services
RUN chown -R docker-user:docker-user /var/www/html && \
    chown -R docker-user:docker-user /var/run/apache2 && \
    chown -R docker-user:docker-user /var/log/apache2 && \
    chown -R docker-user:docker-user /var/lock/apache2 && \
    usermod -aG sudo docker-user && \
    echo "docker-user ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 
# Expose the required ports
EXPOSE 22 80
 
# Start the SSH and Apache services
CMD service ssh start && /usr/sbin/apache2ctl -D FOREGROUND

After we have defined our Dockerfile, we need to convert it into an image. With the build command, we take the directory with the Dockerfile, execute the steps from the Dockerfile, and store the image in our local Docker Engine. If one of the steps fails due to an error, the container creation will be aborted. With the option -t, we give our container a tag, so it is easier to identify and work with later.

Docker Build

  Docker Build

ataker@htb[/htb]$ docker build -t FS_docker

Once the Docker image has been created, it can be executed through the Docker engine, making it a very efficient and easy way to run a container. It is similar to the virtual machine concept, based on images. Still, these images are read-only templates and provide the file system necessary for runtime and all parameters. A container can be considered a running process of an image. When a container is to be started on a system, a package with the respective image is first loaded if unavailable locally. We can start the container by the following command docker run:

Docker Run - Syntax

  Docker Run - Syntax

ataker@htb[/htb]$ docker run -p <host port>:<docker port> -d <docker container name>

Docker Run

  Docker Run

ataker@htb[/htb]$ docker run -p 8022:22 -p 8080:80 -d FS_docker

In this case, we start a new container from the image FS_docker and map the host ports 8022 and 8080 to container ports 22 and 80, respectively. The container runs in the background, allowing us to access the SSH and HTTP services inside the container using the specified host ports.

From Repos (Not recommended)

sudo apt install docker.io 

sudo systemctl enable --now docker
sudo usermod -aG docker $USER

sudo apt install docker-compose-v2

Since maintained by the repo itself, not docker, can be old and conflicting

With Scrijpt (Not Recommended)

curl -sSL https://get.docker.com | sh

It does the same thing with manual install, but automize it so you can’t control.

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