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Rootless Docker installation steps in Linux terminal

Installing Docker on Linux

by BinarybrainsContainerization

1. What Is Docker & Why Install It on Linux?

Docker is a containerization platform enabling lightweight, isolated environments to build, ship, and run applications consistently. Since it relies on Linux kernel features like namespaces and cgroups, native Linux distributions deliver best performance, compatibility, and security.

Use Docker on Linux to:

  • Simplify development and deployment, identical across environments

  • Maximize resource efficiency, with lightweight virtualization

  • Leverage open-source ecosystems like Ubuntu, CentOS, Fedora, and more

2. Pre-Installation Essentials

Before installing Docker, make sure you:

  • Run a 64-bit, up-to-date Linux kernel

  • Have sudo/admin rights

  • On Ubuntu/Debian: add Docker’s GPG key, apt repository 

  • On RHEL distros: enable EPEL and yum/dnf repositories

  • Optionally install Docker’s get.docker.com convenience script (optional)

3. Installing Docker on Ubuntu (20.04 / 22.04 / 24.04)

1. Update packages:

sudo apt update
sudo apt install \
ca-certificates \
curl \
gnupg \
lsb-release

2. Add Docker’s GPG key & stable repo:

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

3. Install Docker Engine:

sudo apt update
sudo apt install docker-ce docker-ce‑cli containerd.io docker-compose-plugin

4. Verify installation:

sudo docker run hello‑world

4. Installing on CentOS / RHEL / AlmaLinux

Set up repo:

sudo dnf install -y yum-utils
sudo yum-config-manager \
–add-repo \
https://download.docker.com/linux/centos/docker-ce.repo

Install Docker:

sudo dnf install docker-ce docker-ce-cli containerd.io

Start services:

sudo systemctl start docker
sudo systemctl enable docker

Test:

sudo docker run hello‑world

5. Installing on Fedora

Fedora is well-supported for Docker CE.

1. Add Docker repo:

sudo dnf config-manager \
–add-repo \
https://download.docker.com/linux/fedora/docker-ce.repo

2. Install packages:

sudo dnf install docker-ce docker-ce-cli containerd.io

3. Enable & verify:

sudo systemctl enable –now docker
sudo docker run hello‑world

6. Rootless Docker – Running Without Root

Most Docker setups need root. Rootless Docker enables the daemon and containers to run under a normal user, enhancing security 

Steps to install:

  1. Ensure support packages are installed (uidmap, dbus-user-session, fuse-overlayfs) 

  2. As a normal user:
    curl -fsSL https://get.docker.com/rootless | sh

  3. Follow script instructions to add env vars to .bashrc or .zshrc, then enable the systemd user service:
    systemctl –user enable docker
    loginctl enable-linger $(whoami)

  4. Test:
    docker run hello‑world
    docker run -p 8080:80 nginx

7. Running Docker Without Sudo: Docker Group

To manage Docker as a normal user (without rootless mode), add your user to the docker group:
sudo groupadd docker
sudo usermod -aG docker $USER
newgrp docker # Or logout/login
docker run hello-world

8. Post-Install Configuration

Configure essential settings after installation :

  • Start on boot:
    sudo systemctl enable docker containerd

  • Configure log rotation in /etc/docker/daemon.json:
    {
    “log-driver”: “json-file”,
    “log-opts”: {
    “max-size”: “10m”,
    “max-file”: “3”
    }
    }

  • User namespace mapping for security
  • Proxy settings, if required

9. Security & Best Practices

Docker Host Hardening

  • Use minimal Linux distros (Alpine, Fedora CoreOS) 

  • Keep kernel & packages patched

  • Enable SELinux / AppArmor / Seccomp

Container Best Practices

  • Run as non-root inside containers (USER appuser) 

  • Drop unnecessary Linux capabilities (--cap-drop=ALL) 

  • Scan images regularly (Trivy, Docker Scout)

  • Use read-only file systems: --read-only

  • Manage secrets securely (not env vars)

Rootless Mode

  • Suitable for developer environments

  • Be aware of networking and driver limitations

  • Podman may be a better rootless alternative

Conclusion

You now have a full-featured Docker setup on Linux:

  • Stable installation on Ubuntu, CentOS, Fedora

  • Rootless Docker for enhanced user-space security

  • Post-configurations to optimize usability

  • Security guidance for safe container operations

  • Group-based access via Docker group

  • Image placement best practices for readability

🚀 Take Action:

  • Deploy your first container

  • Apply security settings

  • Consider rootless or Podman for sandboxed dev work

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