How to configure Jenkins job to build with Docker? - docker

Question

I'm attempting to build a branch using Jenkins and a 'docker in the docker' container to build a container from src.
I define the Docker cloud instance here:
Should an extra tab be available that enable the job to use the Docker cloud instance setup above?
The job is a multi-branch pipeline:
But when I attempt to configure a job that uses the docker cloud instance, configured above, the option to build with docker is not available:
The build log contains:
time="2021-04-04T14:27:16Z" level=error msg="failed to dial gRPC:
cannot connect to the Docker daemon. Is 'docker daemon' running on
this host?: dial unix /var/run/docker.sock: connect: no such file or
directory" error during connect: Post
http://%2Fvar%2Frun%2Fdocker.sock/v1.40/build?buildargs=%7B%7D&cachefrom=%5B%5D&cgroupparent=&cpuperiod=0&cpuquota=0&cpusetcpus=&cpusetmems=&cpushares=0&dockerfile=Dockerfile&labels=%7B%7D&memory=0&memswap=0&networkmode=default&rm=1&session=vgpahcarinxfh05klhxyk02gg&shmsize=0&t=ron%2Fml-services&target=&ulimits=null&version=1:
context canceled [Pipeline] } [Pipeline] // stage [Pipeline] }
[Pipeline] // node [Pipeline] End of Pipeline [Bitbucket] Notifying
commit build result [Bitbucket] Build result notified ERROR: script
returned exit code 1 Finished: FAILURE
which suggests the build is searching for Docker on the same host as Jenkins, but I'm attempting to build with Docker on a different host?
Have I configured Docker with Jenkins correctly?
My Jenkinsfile contains:
node {
def app
stage('Clone repository') {
checkout scm
}
stage('Build image') {
app = docker.build("ron/services")
}
stage('Push image') {
docker.withRegistry('https://registry.hub.docker.com', 'git') {
app.push("${env.BUILD_NUMBER}")
app.push("latest")
}
}
}
Update:
Clicking the checkmark at Expose DOCKER_HOST , rebuilding contains error:
+ docker build -t ron/services .
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
[Bitbucket] Notifying commit build result
[Bitbucket] Build result notified
ERROR: script returned exit code 1
Finished: FAILURE

Answer 1

The docker cli tries to connect using the docker socket in /var/run. This means that no external daemon is configured, for example using the environment variable DOCKER_HOST.
Try clicking the checkmark at Expose DOCKER_HOST.

Answer 2

Not clear if this is what you are trying to do, but configuring Docker cloud will tell your Jenkins to launch a container on 10.241.0.198 (client), and run your jenkins job in that container. To make this work, there are a couple of things to check:
ensure that jenkins user on jenkins server can access port 2371 on client, ie 'Test Connection' returns success
Turn on 'Expose DOCKER_HOST' if you want to use docker in the container
configure ssh so that jenkins user on jenkins server can ssh to the container when it's running on the client (CMD ["/usr/sbin/sshd", "-D"] in Dockerfile)
In Docker Agent Template: configure a label; turn on 'enabled'; configure a docker image to run in the container; set Remote filesystem Root: /home/jenkins
In Container Settings: (very important!!) add /var/run/docker.sock:/var/run/docker.sock to Volumes
To get your Pipeline job to run on the docker image, set the agent label to the label you provided in step 4.
A couple of gotchas when creating the image to run in the container:
install both openssh-clients and openssh-server
install java
install any other build tools you might need, eg git
install docker if you want docker in docker support
configure for sftp in /etc/ssh/sshd_config eg, Add
# override default of no subsystems
Subsystem sftp /usr/lib/openssh/sftp-server
Match group sftp
X11Forwarding no
AllowTCPForwarding no
ForceCommand internal-sftp