Jenkins pipeline: permission denied on the Docker daemon socket

TL;DR

Add the agent user to the docker group with sudo usermod -a -G docker jenkins, then restart the Jenkins agent process, because group membership only takes effect in new sessions. Verify with the groups command or by checking the docker line in /etc/group.

Steps

1. Add the agent user to the docker group with sudo usermod -a -G docker jenkins, then restart the Jenkins agent process, because group membership only takes effect in new sessions. Verify with the groups command or by checking the docker line in /etc/group. If the agent itself runs in a container with the socket mounted, make sure the container user is in the docker group as well.

When to use

You are seeing this: Verify with the groups command or by checking the docker line in /etc/group. Use this skill when you run into "Jenkins pipeline: permission denied on the Docker daemon socket".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Source: Stack Overflow #47854463 (accepted answer, 642 votes): a pipeline step using docker.image(...).inside fails with Got permission denied while trying to connect to the Docker daemon socket. The agent process runs as the jenkins user, which is not a member of the docker group, so it cannot talk to the daemon.

Verified resolution: Add the agent user to the docker group with sudo usermod -a -G docker jenkins, then restart the Jenkins agent process, because group membership only takes effect in new sessions. Verify with the groups command or by checking the docker line in /etc/group. If the agent itself runs in a container with the socket mounted, make sure the container user is in the docker group as well.

Source URL: https://stackoverflow.com/questions/47854463/docker-got-permission-denied-while-trying-to-connect-to-the-docker-daemon-socke