How to Get Rid of the 'Cannot Connect to the Docker Daemon” Error - MiniTool

Five ways to solve the failure of Docker connection daemon

When building and running a software container with Docker, you may encounter an error message "Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the Docker daemon running?" This article will provide several solutions.

Docker is an open platform for developing, publishing, and running applications, which allows you to separate applications from your infrastructure to deliver software quickly. After installing Docker, you may encounter the above error. Possible reasons include:

• The Docker daemon is not running.
• Docker is not cleanly closed.
• Missing root permission to start Docker service.

Here are a few ways to fix this error:

Method 1: Use systemctl to start Docker service

If you have a new Docker installed on Ubuntu, the Docker service may not be running. systemctl command replaces the old SysV init system to manage systemd services running on Linux systems. If you do not have systemctl on your system, please install it first. This method is only for users who install Docker using the APT package manager. If you install Docker through SNAP, please refer to Method 2.

Step 1: Open the terminal.

Step 2: Execute the following commands in turn and press Enter after each command:

• sudo systemctl unmask docker
• systemctl start docker
• systemctl status docker

Then, check if the "Unable to connect to Docker daemon" issue is resolved.

Method 2: Use Snap to start Docker service

If you have Docker installed using Snap package manager, you can use the snap command to manage the docker daemon.

Step 1: Open the terminal.

Step 2: Execute the following commands in turn and press Enter after each command:

• sudo snap start docker
• sudo snap services

Step 3: If the above command is invalid, try connecting to the docker:home plugin (it will not automatically connect by default). After the connection is complete, start the Docker service. Then, run the following command:

• sudo snap connect docker:home :home
• sudo snap start docker

Method 3: Clean up "Docker pull failed" and start Docker service

In some cases, you may accidentally close Docker while pulling the container. This situation will block docker.service and docker.socket files. Before starting docker, you need to unmask two unit files - docker.service and docker.daemon .

Step 1: Start the terminal and execute the following command:

• systemctl unmask docker.service
• systemctl unmask docker.socket
• systemctl start docker.service

Step 2: Then, execute the following command:

• sudo su
• service docker stop
• cd /var/run/docker/libcontainerd
• rm -rf containerd/*
• rm -f docker-containerd.pid
• service docker start

Method 4: Start Docker for users without root permissions

You can try exporting Docker host variables to localhost via port 2375. You need to execute the command export DOCKER_HOST=tcp://localhost:2375 .

Method 5: Reinstall Docker

If the above solution is invalid, it is recommended to reinstall Docker. You can visit the official website to do it.

Summarize

The above are some common solutions to fix the Docker daemon in Docker that cannot connect to unix:///var/run/docker.sock. Is the Docker daemon running? If you have other useful ways to resolve this error, please leave a message below to let us know.

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