[jenkins] Initial commit of self-upgrading Jenkins

jenkins/Dockerfile

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+FROM itzg/ubuntu-openjdk-7
+
+MAINTAINER itzg
+
+RUN DEBIAN_FRONTEND=noninteractive apt-get -y install curl && apt-get clean
+
+ADD download-and-start.sh /download-and-start
+
+ENV JENKINS_HOME /data
+VOLUME ["/data"]
+EXPOSE 8080
+
+CMD ["/download-and-start"]

jenkins/README.md

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+A self-upgrading [Jenkins CI](http://jenkins-ci.org/) server
+
+# Basic Usage
+
+To start Jenkins with the latest version:
+
+    ID=$(docker run -d -p 8080:8080 itzg/jenkins)
+
+At a later time, you can upgrade by restarting the container:
+
+    docker stop $ID
+    docker start $ID
+
+# Attaching host directory to Jenkins home directory
+
+The Jenkins home directory is attachable at `/data`, so attaching to a host volume
+would be:
+
+    ID=$(docker run -d -p 8080:8080 -v /SOME_HOST_DIR:/data itzg/jenkins
+
+# Entering the container to perform manual config
+
+As with any Docker container, you can run a shell within the running container:
+
+    docker exec -it $ID bash

jenkins/download-and-start.sh

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+#!/bin/bash
+
+mirrorUrl=http://mirrors.jenkins-ci.org/war/latest/jenkins.war
+url=$(curl -s --head $mirrorUrl|awk -F': ' '$1 == "Location" { print $2 }' | sed 's/[[:space:]]*$//')
+version=$(echo $url | sed 's#.*/war/\(.*\)/jenkins.war#\1#')
+
+mkdir -p /opt/jenkins
+trackingFile=/opt/jenkins/INSTALLED
+
+installed=
+if [ -f $trackingFile ]; then
+  installed=$(cat $trackingFile)
+  echo "Version installed is $installed"
+fi
+
+if [ $version != "$installed" ]; then
+  echo "Downloading $version from '$url'"
+  while ! curl -s -o /opt/jenkins/jenkins.war "$url"
+  do
+    echo "Trying again in 5 seconds"
+    sleep 5
+  done
+
+  echo $version > $trackingFile
+fi
+
+
+cd /opt/jenkins
+exec java -jar jenkins.war