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

Question

I'm using Gitlab and Docker to get continuous integration to my spring boot application and I'm getting this error:

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

.development.env:

export SPRING_ACTIVE_PROFILE='development'
export DOCKER_REPO='DOCKER_HUB_ID/app_name:dev'
export APP_NAME='app_name_dev'
export PORT='8080'
export SERVER_IP='xxx.xxx.xx.xxx'                 #SERVER_IP
export SERVER_SSH_KEY="$DEV_SSH_PRIVATE_KEY"
export DOCKER_HOST='tcp://xxx.xxx.xx.xxx:2375'    #SERVER_IP

.gitlab-ci.yml

services:
  - docker:19.03.7-dind

stages:
  - build and push docker image

docker build:
  image: docker:stable
  stage: build and push docker image
  before_script:
    - source .${CI_COMMIT_REF_NAME}.env    #.development.env
  script:
    - docker build --build-arg SPRING_ACTIVE_PROFILE=$SPRING_ACTIVE_PROFILE -t $DOCKER_REPO .
    - docker login -u $DOCKER_USER -p $DOCKER_PASSWORD docker.io
    - docker push $DOCKER_REPO

This is the whole logs from gitlab:

Running with gitlab-runner 13.5.0 (ece86343)
  on gitlab-server JuhWVkPJ
Preparing the "docker" executor
00:38
Using Docker executor with image docker:stable ...
Starting service docker:19.03.7-dind ...
Pulling docker image docker:19.03.7-dind ...
Using docker image sha256:14af3ba31e635475ec8f7fbe17470424514777621e627a91c41bbbe028dbae16 for docker:19.03.7-dind with digest docker@sha256:2683fcdf7480ea101415833f7793fb058c5f20227890a953b0a70bfc350af5bc ...
Waiting for services to be up and running...
*** WARNING: Service runner-juhwvkpj-project-13-concurrent-0-7c99eb8ace2e2ae6-docker-0 probably didn't start properly.
Health check error:
service "runner-juhwvkpj-project-13-concurrent-0-7c99eb8ace2e2ae6-docker-0-wait-for-service" timeout
Health check container logs:
Service container logs:
2020-12-30T03:14:07.879506461Z Generating RSA private key, 4096 bit long modulus (2 primes)
2020-12-30T03:14:08.459745140Z ..............................................++++
2020-12-30T03:14:08.673203110Z ..................++++
2020-12-30T03:14:08.673231544Z e is 65537 (0x010001)
2020-12-30T03:14:08.713960023Z Generating RSA private key, 4096 bit long modulus (2 primes)
2020-12-30T03:14:08.851463609Z ..............++++
2020-12-30T03:14:09.403244538Z .....................................................++++
2020-12-30T03:14:09.403286293Z e is 65537 (0x010001)
2020-12-30T03:14:09.516423752Z Signature ok
2020-12-30T03:14:09.516463300Z subject=CN = docker:dind server
2020-12-30T03:14:09.516471290Z Getting CA Private Key
2020-12-30T03:14:09.536975767Z /certs/server/cert.pem: OK
2020-12-30T03:14:09.553642146Z Generating RSA private key, 4096 bit long modulus (2 primes)
2020-12-30T03:14:09.927078677Z ...................................................++++
2020-12-30T03:14:10.107451624Z ...................++++
2020-12-30T03:14:10.108457646Z e is 65537 (0x010001)
2020-12-30T03:14:10.156096074Z Signature ok
2020-12-30T03:14:10.156125397Z subject=CN = docker:dind client
2020-12-30T03:14:10.156302268Z Getting CA Private Key
2020-12-30T03:14:10.178703934Z /certs/client/cert.pem: OK
2020-12-30T03:14:10.194290163Z mount: permission denied (are you root?)
2020-12-30T03:14:10.194438175Z Could not mount /sys/kernel/security.
2020-12-30T03:14:10.194456604Z AppArmor detection and --privileged mode might break.
2020-12-30T03:14:10.195933829Z mount: permission denied (are you root?)
*********
Pulling docker image docker:stable ...
Using docker image sha256:b0757c55a1fdbb59c378fd34dde3e12bd25f68094dd69546cf5ca00ddbaa7a33 for docker:stable with digest docker@sha256:fd4d028713fd05a1fb896412805daed82c4a0cc84331d8dad00cb596d7ce3e3a ...
Preparing environment
00:01
Running on runner-juhwvkpj-project-13-concurrent-0 via gitlab-server...
Getting source from Git repository
00:03
Fetching changes with git depth set to 50...
Reinitialized existing Git repository in /builds/abdallah/harvis/.git/
Checking out 5568bbc9 as DM_Module...
Skipping Git submodules setup
Executing "step_script" stage of the job script
00:36
$ source .${CI_COMMIT_REF_NAME}.env
$ whoami
root
$ docker build --build-arg SPRING_ACTIVE_PROFILE=$SPRING_ACTIVE_PROFILE -t $DOCKER_REPO .
Cannot connect to the Docker daemon at tcp://xxx.xxx.xx.xxx:2375. Is the docker daemon running?
Cleaning up file based variables
00:01
ERROR: Job failed: exit code 1

I think the error is in DOCKER_HOST, what should I assign it? I'd appreciate any help or suggestion.

None of the 100+ results of a search for cannot connect to the docker daemon at tcp here were able to help? — Ken White
If you have access to GitLab runners, try to replicate the environment on the runner manually, Also to use docker in docker you have to provide "privileged" as "true" in gitlab runner's config. — Ashwani

Sajith Silva Sajith Silva · Accepted Answer · 2020-12-30T04:14:31

The Docker daemon can listen for Docker Engine API requests via three different types of Socket: unix, tcp, and fd

your docker daemon is trying to connect via tcp (2375), and it seems not enabled.

you need to start docker daemon with -H tcp://<ip>:2375

or put it in /etc/docker/daemon.json

"hosts": ["tcp://<ip>:2375", "unix:///var/run/docker.sock"],

EDIT

Binding to 0.0.0.0 is dangerous as David pointed out.

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

1 Answers

EDIT