Docker Tutorial — Post-Install Steps

After installing Docker Engine on Linux, there are a few important configuration steps to make Docker easier and safer to use.

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Run Docker Without sudo

By default, Docker commands require sudo. Fix this by adding your user to the docker group:

$ sudo usermod -aG docker $USER

# Apply the group change (or log out and back in)
$ newgrp docker

# Verify — no sudo needed
$ docker run hello-world

Why this matters: CI/CD systems and scripts shouldn’t need root access to build containers.

Security note: Members of the docker group have root-equivalent access. Only add trusted users.

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Configure the Docker Daemon

The Docker daemon reads configuration from /etc/docker/daemon.json:

$ sudo mkdir -p /etc/docker
$ sudo tee /etc/docker/daemon.json <<EOF
{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  },
  "storage-driver": "overlay2"
}
EOF

# Restart Docker to apply
$ sudo systemctl restart docker

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Enable Docker on Boot

$ sudo systemctl enable docker
$ sudo systemctl enable containerd

# Verify
$ sudo systemctl is-enabled docker
enabled

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Quick Reference

Add user to docker group:  sudo usermod -aG docker $USER
Daemon config:             /etc/docker/daemon.json
Enable on boot:            sudo systemctl enable docker
Restart daemon:            sudo systemctl restart docker

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