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README.md

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+# Jenkins JNLP Agent Docker image for DianPlus.cn
+
+This is an image for [Jenkins](https://jenkins.io) agent (FKA "slave") using JNLP to establish connection.
+This agent is powered by the [Jenkins Remoting library](https://github.com/jenkinsci/remoting), which version is being taken from the base [Docker Agent](https://github.com/jenkinsci/docker-slave/) image, and customized by DianPlus.cn.
+
+## Running
+
+To run a Docker container
+
+    docker run dianplus/jnlp-slave -url http://jenkins-server:port <secret> <agent name>
+
+To run a Docker container with [Work Directory](https://github.com/jenkinsci/remoting/blob/master/docs/workDir.md):
+
+    docker run dianplus/jnlp-slave -url http://jenkins-server:port -workDir=/home/jenkins/agent <secret> <agent name>
+
+Optional environment variables:
+
+* `JENKINS_URL`: url for the Jenkins server, can be used as a replacement to `-url` option, or to set alternate jenkins URL
+* `JENKINS_TUNNEL`: (`HOST:PORT`) connect to this agent host and port instead of Jenkins server, assuming this one do route TCP traffic to Jenkins master. Useful when when Jenkins runs behind a load balancer, reverse proxy, etc.
+* `JENKINS_SECRET`: agent secret, if not set as an argument
+* `JENKINS_AGENT_NAME`: agent name, if not set as an argument
+* `JENKINS_AGENT_WORKDIR`: agent work directory, if not set by optional parameter `-workDir`
+
+## Configuration specifics
+
+### Enabled JNLP protocols
+
+By default, the [JNLP3-connect](https://github.com/jenkinsci/remoting/blob/master/docs/protocols.md#jnlp3-connect) is disabled due to the known stability and scalability issues.
+You can enable this protocol on your own risk using the 
+`JNLP_PROTOCOL_OPTS=-Dorg.jenkinsci.remoting.engine.JnlpProtocol3.disabled=false` property (the protocol should be enabled on the master side as well).
+
+In Jenkins versions starting from `2.27` there is a [JNLP4-connect](https://github.com/jenkinsci/remoting/blob/master/docs/protocols.md#jnlp4-connect) protocol. 
+If you use Jenkins `2.32.x LTS`, it is recommended to enable the protocol on your instance.