Setup Docker on Ubuntu 25.10

To set up Docker on Ubuntu 25.10 (Questing Quokka), follow these steps. These instructions use the official Docker repository to ensure you get the latest version.

Step 1: Uninstall Old Versions

Conflicting packages (like docker.io or podman-docker) might be installed by default. Remove them to prevent conflicts:

sudo apt-get remove docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc

Step 2: Set Up the Docker Repository

1、Update your package index and install necessary dependencies:

sudo apt-get update
sudo apt-get install ca-certificates curl

2、Add Docker’s official GPG key:

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

3、Add the repository to your sources:
This command automatically detects your Ubuntu version codename (questing for 25.10) and adds the correct repository.

echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

4、Update the package index again to include the new Docker packages:

sudo apt-get update

Step 3: Install Docker Engine

Install the latest version of Docker Engine, containerd, and Docker Compose:

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 4: Verify the Installation

Run the “hello-world” image to verify that Docker is installed and running correctly:

sudo docker run hello-world

Step 5: Run Docker Without Sudo (Optional)

By default, running Docker requires sudo. To run Docker commands as your current user:

1、Create the docker group (it likely already exists):

sudo groupadd docker

2、Add your user to the group:

sudo usermod -aG docker $USER

3、Apply the changes:
Log out and log back in, or run the following command to activate the changes immediately:

newgrp docker

4、Test it:

docker run hello-world

(This should now work without sudo).

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Run a never-exit docker container of ubuntu20.04

The “Tail Null” (Classic)

This is a very common alternative often used in older scripts. It “watches” a file that never changes, keeping the process active.

docker run -d --name my-ubuntu ubuntu:20.04 tail -f /dev/null

How to enter the container

Once your container is running in the background, you can log into it using exec:

docker exec -it my-ubuntu bash