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In this guide, we’ll move beyond the default apt installation and launch Jenkins directly from its WAR file. This approach gives you full control over JVM options, ports, and context paths—ideal for testing or side-by-side instances.

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1. Inspecting the Apt-Installed Jenkins Service

Start by confirming the existing Jenkins process managed via apt: 
ps aux | grep -i jenkins

jenkins   27173  8.4  8.2 10874592 134834 ?      Ssl  17:51   0.58 /usr/bin/java -Xms1G -Xmx1G -jar /usr/share/java/jenkins.war \
    --webroot=/var/cache/jenkins/war --httpPort=8080
root      29978  0.0  0.0  4088  2080 pts/6    S+   18:03   0.00 grep --color=auto -i jenkins
Here you can see:
  • A 1 GB heap (-Xms1G -Xmx1G)
  • The WAR file at /usr/share/java/jenkins.war
  • Webroot under /var/cache/jenkins/war
  • HTTP bound to port 8080
The image shows a Jenkins dashboard displaying a list of various jobs with their statuses, build times, and other details. The interface includes options for running and managing these jobs.

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2. Downloading a Specific Jenkins WAR Version

To try a newer release, browse the Jenkins WAR directory and choose 2.479.3 (released Jan 1, 2025):
The image shows a directory listing from a Jenkins website, displaying various versions of Jenkins with their last modified dates.
Once you’ve picked the version, verify the file and checksum:
The image shows a directory listing on a website, displaying files related to Jenkins, including "jenkins.war" and its SHA256 checksum.
On your Ubuntu server: 
mkdir -p ~/jenkins-war
cd ~/jenkins-war
wget https://get.jenkins.io/war-stable/2.479.3/jenkins.war

# Confirm the download
ls -lh jenkins.war
# -rw-r--r-- 1 root root 92M Jan  8 16:34 jenkins.war

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3. Launching Jenkins with Custom Parameters

By default, java -jar jenkins.war binds to port 8080—which conflicts with the apt-installed service. Override this with: 
java -jar jenkins.war --httpPort=7777 --prefix=/dasher-technologies
After a few seconds, you’ll see Jetty start up and the initial setup wizard prompt: 
2025-02-05 18:09:12.026+0000 [id=1]  INFO  org.eclipse.jetty.server.Server#doStart: Started Server@19c65cdc{STARTING}[12.0.16,sto=0] @1525ms
...
***********************************************************************
Jenkins initial setup is required. An admin user has been created and a password generated.
Please use the following password to proceed to installation:
456e352c1ea424f9bfc923315957c2
This may also be found at: /root/.jenkins/secrets/initialAdminPassword
***********************************************************************
Save the generated password. You can always retrieve it later from /root/.jenkins/secrets/initialAdminPassword.

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4. Unlocking Jenkins and Installing Plugins

Open your browser at: 
http://localhost:7777/dasher-technologies
Enter the admin password when prompted. The setup wizard will then let you:
  • Install Suggested Plugins
  • Select Plugins to customize your install
The image shows a Jenkins setup wizard screen with options to "Install suggested plugins" or "Select plugins to install."

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5. Common Startup Options

Jenkins supports various JVM and server flags. Below are frequently used HTTP/HTTPS settings:
OptionDescriptionExample
--httpPort=<port>Bind HTTP server to this port--httpPort=7777
--httpListenAddress=<addr>Set HTTP bind address--httpListenAddress=0.0.0.0
--httpsPort=<port>Enable HTTPS on this port (use -1 to disable)--httpsPort=8443
--httpsListenAddress=<addr>Set HTTPS bind address--httpsListenAddress=0.0.0.0
--prefix=<context-path>Specify the URL prefix (context path)--prefix=/custom-path
--sessionTimeout=<minutes>Define session timeout in minutes--sessionTimeout=30
--httpsKeyStore=<path>Path to your Java keystore for HTTPS/path/to/keystore
--httpsKeyStorePassword=Password for the HTTPS keystoreYourPassword
For the complete list of server options, see Jenkins HTTP Server Options.

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6. Verifying Multiple Jenkins Instances

In another terminal, confirm both the apt-installed and standalone WAR instances are running: 
ps aux | grep -i jenkins

jenkins   27173  5.4  8.8 10874592 1435160 ?     Ssl  17:52   1.02 /usr/bin/java -Xms1G -Xmx1G -jar /usr/share/java/jenkins.war --webroot=/var/cache/jenkins/war --httpPort=8080
root      31980 19.6  5.6 13983116  912304 pts/6 Sl+  18:09   0.21 java -jar jenkins.war --httpPort=7777 --prefix=/dasher-technologies
root      32769  0.0  0.0   4088   1960 pts/8 S+   18:11   0.00 grep --color=auto -i jenkins
You now have two independent Jenkins servers running:
  • Port 8080 via apt
  • Port 7777 with custom context /dasher-technologies
Thank you for following this demo!

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