How to fix Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running? in Docker

DockerINTERMEDIATEMEDIUMUpdated Dec 1, 2025· 248 views

This error occurs when Docker is configured to connect via TCP on port 2375, but the daemon is not listening on that port. This commonly affects WSL, CI/CD pipelines, and Docker-in-Docker setups.

Quick fix

Fixes Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?

echo $DOCKER_HOST

Check your DOCKER_HOST environment variable
For WSL2 users: Use native Docker integration
For WSL1 or intentional TCP connection: Enable TCP in Docker Desktop
For Linux: Configure Docker daemon to listen on TCP

docker — error

$echo $DOCKER_HOST
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?

What this error means

When Docker commands fail with "Cannot connect to the Docker daemon at tcp://localhost:2375", the Docker CLI is attempting to communicate with the Docker daemon over TCP port 2375 instead of the default Unix socket. This TCP connection mode is typically used in specific scenarios: - **WSL (Windows Subsystem for Linux)**: To connect from WSL to Docker Desktop running on Windows - **CI/CD pipelines**: In GitLab CI, Jenkins, or other CI systems using Docker-in-Docker (dind) - **Remote Docker access**: When connecting to a Docker daemon on another machine - **Development tools**: Some IDEs and development tools require TCP access to Docker The error indicates either that the Docker daemon is not running at all, or that it is not configured to listen on the TCP port. By default, Docker listens only on a Unix socket (`/var/run/docker.sock`) for security reasons, as exposing the daemon over TCP without TLS allows anyone with network access to control Docker.

Typical symptoms

Docker commands fail with 'Cannot connect to the Docker daemon at tcp://localhost:2375'
DOCKER_HOST environment variable is set to tcp://localhost:2375
Docker works when run with sudo or on the host, but not from WSL or containers
CI/CD pipeline jobs fail at Docker commands with connection refused errors
Docker-in-Docker (dind) service containers cannot be reached
'docker version' shows only Client info, or fails with connection error

Common causes

DOCKER_HOST environment variable is set to TCP but daemon is not listening on TCP
Docker Desktop 'Expose daemon on tcp://localhost:2375' setting is disabled
WSL2 integration is enabled but DOCKER_HOST is still set to TCP (WSL1 configuration)
Docker daemon is not running at all
Firewall blocking port 2375
In CI/CD: Docker-in-Docker (dind) service is not properly configured
In CI/CD: Using tcp://localhost:2375 instead of tcp://docker:2375 for dind service
Port 2375 is already in use by another application

How to fix "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?"

1Check your DOCKER_HOST environment variable

First, verify if DOCKER_HOST is explicitly set:

bash

echo $DOCKER_HOST

If this returns tcp://localhost:2375 or similar, that's why Docker is trying to connect via TCP.

To unset it temporarily:

bash

unset DOCKER_HOST
docker version

If Docker works after unsetting, the fix is to remove DOCKER_HOST from your shell configuration files (~/.bashrc, ~/.zshrc, ~/.profile).

2For WSL2 users: Use native Docker integration

If you're using WSL2 with Docker Desktop, you should NOT use the TCP connection method. Docker Desktop provides native WSL2 integration:

1. Open Docker Desktop
2. Go to Settings (gear icon)
3. Navigate to Resources > WSL Integration
4. Enable integration for your WSL distribution
5. Click Apply & Restart

Then in your WSL terminal:

bash

# Remove DOCKER_HOST from your shell config
sed -i '/DOCKER_HOST/d' ~/.bashrc
sed -i '/DOCKER_HOST/d' ~/.zshrc

# Reload your shell
source ~/.bashrc

# Verify Docker works
docker version

With WSL2 integration, Docker commands work natively without any environment variables.

3For WSL1 or intentional TCP connection: Enable TCP in Docker Desktop

If you specifically need TCP access (WSL1, or accessing Docker from another application):

1. Open Docker Desktop
2. Go to Settings (gear icon)
3. Check "Expose daemon on tcp://localhost:2375 without TLS"
4. Click Apply & Restart

Warning: This exposes Docker without encryption or authentication. Only use this on trusted networks, and never on publicly accessible machines.

Then verify the connection:

bash

export DOCKER_HOST=tcp://localhost:2375
docker version

4For Linux: Configure Docker daemon to listen on TCP

On Linux, you need to configure the Docker daemon to listen on TCP:

Method 1: Using systemd override (recommended)

Create a systemd drop-in file:

bash

sudo mkdir -p /etc/systemd/system/docker.service.d
sudo nano /etc/systemd/system/docker.service.d/override.conf

Add the following content:

ini

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// -H tcp://127.0.0.1:2375

Then reload and restart Docker:

bash

sudo systemctl daemon-reload
sudo systemctl restart docker

Method 2: Using daemon.json

Edit /etc/docker/daemon.json:

json

{
  "hosts": ["unix:///var/run/docker.sock", "tcp://127.0.0.1:2375"]
}

Then restart Docker:

bash

sudo systemctl restart docker

Security Note: Binding to 127.0.0.1 restricts access to localhost only. Never bind to 0.0.0.0 without TLS and authentication.

5For GitLab CI/CD: Use the correct DOCKER_HOST

In GitLab CI with Docker-in-Docker (dind), the Docker daemon runs as a separate service, not on localhost:

yaml

# .gitlab-ci.yml
image: docker:latest

services:
  - docker:dind

variables:
  # Use 'docker' hostname, not 'localhost'
  DOCKER_HOST: tcp://docker:2375
  # For Docker 19.03+ with TLS:
  # DOCKER_HOST: tcp://docker:2376
  # DOCKER_TLS_CERTDIR: "/certs"

build:
  script:
    - docker version
    - docker build -t myimage .

Important: The hostname docker refers to the dind service container. Using localhost or 127.0.0.1 will fail because the daemon is in a different container.

6For other CI/CD systems: Check service configuration

Different CI/CD systems have different configurations for Docker-in-Docker:

Jenkins:

groovy

pipeline {
  agent {
    docker {
      image 'docker:dind'
      args '--privileged'
    }
  }
  environment {
    DOCKER_HOST = 'tcp://localhost:2375'
  }
}

GitHub Actions:

yaml

jobs:
  build:
    runs-on: ubuntu-latest
    services:
      docker:
        image: docker:dind
        options: --privileged
    steps:
      - name: Build
        env:
          DOCKER_HOST: tcp://docker:2375
        run: docker build .

Bitbucket Pipelines:
Enable Docker in your pipeline configuration and use the default socket, or configure TCP access on the runner.

7Verify the daemon is running and listening

To debug further, check if Docker is running and listening on the expected port:

Check if Docker daemon is running:

bash

# On Linux
sudo systemctl status docker

# On Windows (PowerShell)
Get-Service *docker*

Check if port 2375 is listening:

bash

# On Linux
ss -tlnp | grep 2375
# or
netstat -tlnp | grep 2375

# On Windows (PowerShell)
netstat -an | findstr 2375

Test TCP connection:

bash

curl http://localhost:2375/version
# or
nc -zv localhost 2375

If nothing is listening on port 2375, the daemon needs to be configured to listen on TCP (see previous steps).

8Check for port conflicts

If Docker fails to bind to port 2375, another application might be using it:

Find what's using port 2375:

bash

# On Linux
sudo lsof -i :2375
# or
sudo ss -tlnp | grep 2375

# On Windows (PowerShell as Administrator)
netstat -ano | findstr 2375
# Then find the process
Get-Process -Id <PID>

Common conflicts:
- Another Docker daemon instance
- Docker Desktop already running
- Kubernetes or minikube
- Development tools that proxy Docker

Stop the conflicting application or configure Docker to use a different port.

Advanced notes

Security considerations for TCP access:

Exposing Docker over TCP without TLS (port 2375) is a significant security risk. Anyone who can reach the port can:
- Run arbitrary containers with full root access to the host
- Access all images, containers, and volumes
- Modify Docker networks and potentially pivot to other systems

For production or untrusted networks, always use TLS (port 2376):

1. Generate TLS certificates:

bash

# Create CA and certificates
openssl genrsa -aes256 -out ca-key.pem 4096
openssl req -new -x509 -days 365 -key ca-key.pem -sha256 -out ca.pem
# ... (full certificate generation process)

2. Configure Docker daemon:

json

{
  "hosts": ["unix:///var/run/docker.sock", "tcp://0.0.0.0:2376"],
  "tls": true,
  "tlscacert": "/etc/docker/ca.pem",
  "tlscert": "/etc/docker/server-cert.pem",
  "tlskey": "/etc/docker/server-key.pem",
  "tlsverify": true
}

3. Configure Docker client:

bash

export DOCKER_HOST=tcp://hostname:2376
export DOCKER_TLS_VERIFY=1
export DOCKER_CERT_PATH=~/.docker

WSL1 vs WSL2:
- WSL1 required TCP connection to Docker Desktop
- WSL2 uses native integration (no TCP needed)
- If you upgraded from WSL1 to WSL2, remove old DOCKER_HOST settings

Docker context for managing connections:

bash

# Create a context for TCP connection
docker context create tcp-docker --docker "host=tcp://localhost:2375"

# Switch to it
docker context use tcp-docker

# Switch back to default
docker context use default

Frequently asked questions

What does "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the do" mean?: When Docker commands fail with "Cannot connect to the Docker daemon at tcp://localhost:2375", the Docker CLI is attempting to communicate with the Docker daemon over TCP port 2375 instead of the default Unix socket. This TCP connection mode is typically used in specific scenarios: - WSL (Windows Subsystem for Linux): To connect from WSL to Docker Desktop running on Windows - CI/CD pipelines: In GitLab CI, Jenkins, or other CI systems using Docker-in-Docker (dind) - Remote Docker access: When connecting to a Docker daemon on another machine - Development tools: Some IDEs and development tools require TCP access to Docker The error indicates either that the Docker daemon is not running at all, or that it is not configured to listen on the TCP port. sock) for security reasons, as exposing the daemon over TCP without TLS allows anyone with network access to control Docker.
How do I fix "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the do"?: This error occurs when Docker is configured to connect via TCP on port 2375, but the daemon is not listening on that port. This commonly affects WSL, CI/CD pipelines, and Docker-in-Docker setups.
What causes "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the do"?: DOCKER_HOST environment variable is set to TCP but daemon is not listening on TCP Docker Desktop 'Expose daemon on tcp://localhost:2375' setting is disabled WSL2 integration is enabled but DOCKER_HOST is still set to TCP (WSL1 configuration)
Is the "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the do" error serious?: It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading

📚Docker Official Documentation
📖
Configure the Docker daemon - Docker Docs(Official Docs)
📖
Common troubleshooting topics - Docker Desktop Docs(Official Docs)
💬
Cannot connect to the Docker daemon at tcp://localhost:2375 - Stack Overflow(Stack Overflow)
💬
Cannot connect to the Docker daemon on bash on Ubuntu windows - Stack Overflow(Stack Overflow)
💬
Cannot connect to the Docker daemon - GitLab CI/CD - Stack Overflow(Stack Overflow)
💬
WSL and Docker for Windows - Docker Community Forums(Stack Overflow)
🐙
[WSL] Cannot connect to the Docker daemon at tcp://127.0.0.1:2375 - GitHub Issue(GitHub)
🐙
Cannot connect to the Docker daemon at tcp://localhost:2375 - Docker for Mac(GitHub)
🐙
Expose daemon on tcp://localhost:2375 cannot take effect - GitHub Issue(GitHub)
🐙
MacOS dind can't connect to tcp://docker:2375 - GitHub Issue(GitHub)

How to fix Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running? in Docker

Quick fix

What this error means

Typical symptoms

Common causes

How to fix "Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?"

Advanced notes

Frequently asked questions

Related errors

Official resources & further reading