How to fix Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running? in Docker

First, verify whether the Docker service is active:

# On Linux with systemd
sudo systemctl status docker

# Or check if the process is running
ps aux | grep dockerd

If the service is inactive or the process isn't running, proceed to start it.

Start the Docker daemon using your system's service manager:

# On Linux with systemd
sudo systemctl start docker

# On older systems with SysVinit
sudo service docker start

# On macOS/Windows
# Open Docker Desktop application

After starting, verify it's running with docker info.

To prevent this issue after reboots, enable the Docker service:

sudo systemctl enable docker

This creates a symlink so Docker starts automatically when your system boots.

If Docker runs with sudo but not without it, add your user to the docker group:

sudo usermod -aG docker $USER

Important: Log out and log back in for the group change to take effect. Alternatively, run newgrp docker to activate the group in your current session.

Check that the Docker socket exists and has correct permissions:

ls -la /var/run/docker.sock

The socket should be owned by root:docker with permissions srw-rw----. If permissions are wrong:

sudo chmod 660 /var/run/docker.sock
sudo chown root:docker /var/run/docker.sock