Recently while setting up docker for Hyperledger in WSL2, I got the following error:

====> hyperledger/fabric-peer:2.3.2
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?

After a quick research, it turns out that if you are upgrading from WSL to WSL2, Windows leaves behind a few legacy settings from WSL that causes this issue.

Here is the fix that worked for me:

Step 1: Check if you have the same issue §

1. In WSL2 terminal, run the command: docker info | head -15
2. You should see the following error: ERROR: Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?

Step 2: Check if the fix works for you §

1. Run the command: unset DOCKER_HOST
2. Follow the previous step again. The error should be gone now.

Step 3: Make the fix permanent §

1. Edit the .bashrc script with: vi ~/.bashrc
2. Search for the line with DOCKER_HOST and comment it out like this: # export DOCKER_HOST=tcp://localhost:2375
3. Save the file and reload the terminal settings with source ~/.bashrc

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