what ports Jenkins uses when it's on the docker? - docker

Question

I have a Jenkins docker container running on a ubuntu 20.04 machine.
I have a job on my Jenkins which polls a GitLab repository and uses MVN to deploy it on a Nexus server.
What I want to do is to close all ports in my server so I can reduce the risk of being hacked but I don't know which ports should I leave open apart from 8080 and 50000.
Jenkins: jenkins/jenkins:2.361.1-lts-jdk11
Shell Scripts that jenkins executes:
export MAVEN_HOME=/var/apache-maven-3.8.6
export PATH=$PATH:$MAVEN_HOME/bin
cd myproject
mvn clean package deploy
Thank you in advance.

Answer 1

If you want to check what ports are exposed in the Docker image, you can simply use the docker inspect command.
docker inspect jenkins/jenkins:2.361.1-lts-jdk11
The above command will return the following, here you just search for ExposedPorts.
[
{
"Id": "sha256:729c87ece8d086b05a3a67e1f7b7a7e669c3a50db75ea2440dd6099a3f887111",
"RepoTags": [
"jenkins/jenkins:2.361.1-lts-jdk11"
],
"RepoDigests": [
"jenkins/jenkins#sha256:5508cb1317aa0ede06cb34767fb1ab3860d1307109ade577d5df871f62170214"
],
"Parent": "",
"Comment": "buildkit.dockerfile.v0",
"Created": "2022-09-07T12:02:24.712441461Z",
"Container": "",
"ContainerConfig": {
"Hostname": "",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": null,
"Cmd": null,
"Image": "",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": null,
"OnBuild": null,
"Labels": null
},
"DockerVersion": "",
"Author": "",
"Config": {
"Hostname": "",
"Domainname": "",
"User": "jenkins",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"50000/tcp": {},
"8080/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/opt/java/openjdk/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"LANG=C.UTF-8",
"JENKINS_HOME=/var/jenkins_home",
"JENKINS_SLAVE_AGENT_PORT=50000",
"REF=/usr/share/jenkins/ref",
"JENKINS_VERSION=2.361.1",
"JENKINS_UC=https://updates.jenkins.io",
"JENKINS_UC_EXPERIMENTAL=https://updates.jenkins.io/experimental",
"JENKINS_INCREMENTALS_REPO_MIRROR=https://repo.jenkins-ci.org/incrementals",
"COPY_REFERENCE_FILE_LOG=/var/jenkins_home/copy_reference_file.log",
"JAVA_HOME=/opt/java/openjdk"
],
"Cmd": null,
"Image": "",
"Volumes": {
"/var/jenkins_home": {}
},
"WorkingDir": "",
"Entrypoint": [
"/usr/bin/tini",
"--",
"/usr/local/bin/jenkins.sh"
],
"OnBuild": null,
"Labels": {
"org.opencontainers.image.description": "The Jenkins Continuous Integration and Delivery server",
"org.opencontainers.image.licenses": "MIT",
"org.opencontainers.image.revision": "00d1edcbf6e0bd78ff5b359731310b91bdac9b07",
"org.opencontainers.image.source": "https://github.com/jenkinsci/docker",
"org.opencontainers.image.title": "Official Jenkins Docker image",
"org.opencontainers.image.url": "https://www.jenkins.io/",
"org.opencontainers.image.vendor": "Jenkins project",
"org.opencontainers.image.version": "2.361.1"
}
},
"Architecture": "amd64",
"Os": "linux",
"Size": 463047412,
"VirtualSize": 463047412,
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/b87f7dbd3ccb73d1d498c6c4776983a4a9987ed321a7879bbba8f1fc6b24c349/diff:/var/lib/docker/overlay2/dbe3badbc23d551bc9c75baf27268489a6aad4b20430ac97ef2e1aad55a8fc07/diff:/var/lib/docker/overlay2/ae3db8be1ef114178bafc0054933f73dcc2672f9dd1fe4a86a1391a5669ee0ed/diff:/var/lib/docker/overlay2/963904c7b1cd906120b6dc3fbefcbf954735d95cdbc81358909ca0ad891a996b/diff:/var/lib/docker/overlay2/da6f957a0563ce381dece995353e75e3bc94ad048892dcfa831f8a2e41528815/diff:/var/lib/docker/overlay2/7a963ecdeabc85980fbc61bc401818a58572eb3856885542ab9b3ecd7e3f2205/diff:/var/lib/docker/overlay2/9024a41086f6c2fa44bafc813dcbcebd01c83124a7da1e245d5b274b33aa43ff/diff:/var/lib/docker/overlay2/e2ee20b24525e750dc228ea17e3ac7debab0db6b11a4a113bec7737b9e4cd1af/diff:/var/lib/docker/overlay2/9ac2fb80407369d732fce5756bc6f7509874ae8072a5b368bc396757978f0773/diff:/var/lib/docker/overlay2/16c96992e082851b7745a3697da020f7ff7b2c0b11a85bbcff577a5c0018d6a1/diff:/var/lib/docker/overlay2/90477c9091098ece50aa59df3c6965984c3db0ad92f41817fb2cb6d410f68d5e/diff:/var/lib/docker/overlay2/953b244f3ee262704ce382a6edc573e4d0c2713c3311448bbc5fd6799a3217a1/diff:/var/lib/docker/overlay2/98b91e296c5b64b6d46d07e5e3f2a1ce93df7eb475d679a7e7c6c5ee34e05848/diff",
"MergedDir": "/var/lib/docker/overlay2/f4c663aa276a1d387f6d6b83d2bdb8b930d611eb1b0908b7968af790b1953b93/merged",
"UpperDir": "/var/lib/docker/overlay2/f4c663aa276a1d387f6d6b83d2bdb8b930d611eb1b0908b7968af790b1953b93/diff",
"WorkDir": "/var/lib/docker/overlay2/f4c663aa276a1d387f6d6b83d2bdb8b930d611eb1b0908b7968af790b1953b93/work"
},
"Name": "overlay2"
},
"RootFS": {
"Type": "layers",
"Layers": [
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"sha256:be8aebf98af007c3edf440d82b08eedf280e5e87fea260e66095577faf8be7af"
]
},
"Metadata": {
"LastTagTime": "0001-01-01T00:00:00Z"
}
}
]