Installing Docker CE on Rocky Linux 9.6

This guide walks you through installing Docker Community Edition on a Rocky Linux 9.6 VM. If you're using GitHub Codespaces, skip this—Docker is already installed.

Prerequisites

Rocky Linux 9.6 VM with sudo access
Internet connectivity
At least 2GB RAM, 10GB disk space

Step 1: Remove Old Docker Versions (if any)

If you have older Docker packages installed, remove them first:

sudo dnf remove -y docker \
    docker-client \
    docker-client-latest \
    docker-common \
    docker-latest \
    docker-latest-logrotate \
    docker-logrotate \
    docker-engine \
    podman \
    runc

Note: Rocky Linux 9.6 comes with Podman by default. We're removing it to avoid confusion, though Docker and Podman can coexist.

Step 2: Install Required Packages

Install dnf-plugins-core to manage repositories:

sudo dnf install -y dnf-plugins-core

Step 3: Add the Docker Repository

Add the official Docker CE repository:

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

Why RHEL repo? Rocky Linux 9 is binary-compatible with RHEL 9, so the RHEL Docker packages work perfectly. For Rocky 9.x, we use the RHEL repository instead of CentOS.

Step 4: Install Docker CE

Install Docker Engine, CLI, containerd, and Compose plugin:

sudo dnf install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

When prompted about GPG keys, verify the fingerprint matches:

060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35

Type y to accept.

Step 5: Start and Enable Docker

Start the Docker service and enable it to start on boot:

sudo systemctl start docker
sudo systemctl enable docker

Verify it's running:

sudo systemctl status docker

You should see active (running) in green.

Step 6: Add Your User to the Docker Group

By default, Docker requires root. Add your user to the docker group to run without sudo:

sudo usermod -aG docker $USER

Important: Log out and log back in for this to take effect, or run:

newgrp docker

Step 7: Verify Installation

Test that Docker works without sudo:

docker --version
docker run hello-world

Expected output:

Hello from Docker!
This message shows that your installation appears to be working correctly.
...

Also verify Docker Compose:

docker compose version

Troubleshooting

"Permission denied" when running docker

You either:

Didn't add your user to the docker group
Didn't log out and back in after adding

Fix:

sudo usermod -aG docker $USER
# Then log out and log back in

Docker service won't start

Check the logs:

sudo journalctl -u docker.service -n 50

Common causes:

Conflicting container runtime (podman)
Disk space issues
SELinux blocking (check with sudo ausearch -m avc -ts recent)

"No space left on device"

Docker stores images and containers in /var/lib/docker. Check disk space:

df -h /var/lib/docker

Clean up unused resources:

docker system prune -a

SELinux Issues

If you see SELinux denials, you have options:

Option 1: Set SELinux to permissive (not recommended for production):

sudo setenforce 0

Option 2: Install Docker SELinux policy (usually pre-installed on Rocky 9.6):

sudo dnf install -y container-selinux

Note: Rocky Linux 9.6 typically has better SELinux integration with containers out of the box.

Optional: Configure Docker

Change Docker's Storage Location

If you want Docker to store data on a different disk:

Stop Docker:
```
sudo systemctl stop docker
```

Create/edit /etc/docker/daemon.json:

{
  "data-root": "/path/to/new/location"
}

Move existing data (if any):

sudo mv /var/lib/docker /path/to/new/location

Start Docker:
```
sudo systemctl start docker
```

Enable Live Restore

Keep containers running when Docker daemon restarts:

Edit /etc/docker/daemon.json:

{
  "live-restore": true
}

Restart Docker:

sudo systemctl restart docker

Verification Checklist

Before proceeding to the labs, verify:

docker --version shows Docker version 24.x or newer (25.x recommended for Rocky 9.6)
docker compose version shows Compose v2.x
docker run hello-world works without sudo
docker ps returns an empty list (no errors)

Next Steps

Return to the Week 1 README and proceed to Lab 1.