Jenkins WAR file execution - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to start Jenkins using the WAR file.

Jenkins

java -jar [1]

Drag options to blanks, or click blank then click option'

Ajenkins.zip

Bjenkins.jar

Cjenkins.war

Djenkins.exe

Attempts:

3 left

💡 Hint

Common Mistakes

Using .jar or .exe instead of .war

Trying to run the WAR file without 'java -jar'

The Jenkins WAR file is named jenkins.war. Running java -jar jenkins.war starts Jenkins.

2fill in blank

medium

Complete the command to run Jenkins on port 8081 instead of the default port.

Jenkins

java -jar jenkins.war --httpPort=[1]

Drag options to blanks, or click blank then click option'

A8081

B9090

C443

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 which requires root privileges

Using port 443 which is for HTTPS

Using --httpPort=8081 tells Jenkins to listen on port 8081 instead of the default 8080.

3fill in blank

hard

Complete the command to run Jenkins with a custom URL prefix.

Jenkins

java -jar jenkins.war --prefix=[1]

Drag options to blanks, or click blank then click option'

A/home/jenkins

B/var/jenkins_home

C/jenkins_home

D/custom_home

Attempts:

3 left

💡 Hint

Common Mistakes

Using file system paths instead of URL paths for --prefix

Confusing home directory with URL prefix

The --prefix option sets the URL prefix, not the home directory. To set the home directory, use the environment variable JENKINS_HOME. Use /custom_home as a URL prefix example.

4fill in blank

hard

Fill both blanks to run Jenkins on port 9090 with a custom prefix URL.

Jenkins

java -jar jenkins.war --httpPort=[1] --prefix=[2]

Drag options to blanks, or click blank then click option'

A9090

B8080

C/jenkins

D/custom

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up port numbers

Using file system paths instead of URL prefixes

To run Jenkins on port 9090 with a URL prefix /jenkins, use --httpPort=9090 and --prefix=/jenkins.

5fill in blank

hard

Fill all three blanks to run Jenkins with a custom home directory, on port 8085, and with a prefix URL.

Jenkins

JENKINS_HOME=[1] java -jar jenkins.war --httpPort=[2] --prefix=[3]

Drag options to blanks, or click blank then click option'

A/var/lib/jenkins

B8085

C/ci

D/home/jenkins

Attempts:

3 left

💡 Hint

Common Mistakes

Using URL paths for home directory

Using default port instead of 8085

Omitting the prefix or using wrong format

Set the environment variable JENKINS_HOME to /var/lib/jenkins to specify the Jenkins home directory. Run Jenkins on port 8085 with the prefix URL /ci.

Practice

1. What does running java -jar jenkins.war do in Jenkins?

easy

A. Deletes Jenkins configuration files

B. Installs Jenkins permanently on the system

C. Updates Jenkins to the latest version

D. Starts Jenkins server without installing it

Solution

1. Step 1: Understand the command purpose

   The command java -jar jenkins.war runs the Jenkins server directly from the WAR file without installation.

2. Step 2: Differentiate from installation

   This method does not install Jenkins permanently but starts it temporarily for use or testing.

3. Final Answer:

   Starts Jenkins server without installing it -> Option D

4. Quick Check:

   Run WAR file = Start Jenkins temporarily [OK]

Hint: WAR file runs Jenkins without install, just start it [OK]

Common Mistakes:

• Thinking it installs Jenkins permanently
• Confusing it with Jenkins update command
• Assuming it deletes files

2. Which command correctly starts Jenkins on port 9090 using the WAR file?

easy

A. java -jar jenkins.war --httpPort=9090

B. java -jar jenkins.war -p 9090

C. java -jar jenkins.war --port 9090

D. java -jar jenkins.war -httpPort 9090

Solution

1. Step 1: Recall Jenkins WAR port option syntax

   The correct option to specify port is --httpPort=9090 when running the WAR file.

2. Step 2: Check other options for correctness

   Options B, C, and D use incorrect flags or syntax not recognized by Jenkins WAR execution.

3. Final Answer:

   java -jar jenkins.war --httpPort=9090 -> Option A

4. Quick Check:

   Use --httpPort=number to set port [OK]

Hint: Use --httpPort=PORT to set Jenkins port [OK]

Common Mistakes:

• Using -p or --port which Jenkins WAR does not recognize
• Missing equal sign in option
• Using single dash for long option

3. What will be the output if you run java -jar jenkins.war --httpPort=8080 when port 8080 is already in use?

medium

A. Error: Address already in use, Jenkins fails to start

B. Jenkins automatically switches to port 8081

C. Jenkins starts successfully on port 8080

D. Jenkins ignores the port option and uses default

Solution

1. Step 1: Understand port conflict behavior

   If the specified port (8080) is busy, Jenkins cannot bind to it and will fail to start with an error.

2. Step 2: Check Jenkins automatic port fallback

   Jenkins WAR does not automatically switch ports; it requires manual change if port is busy.

3. Final Answer:

   Error: Address already in use, Jenkins fails to start -> Option A

4. Quick Check:

   Port busy = Jenkins start error [OK]

Hint: Busy port causes Jenkins start error, no auto-switch [OK]

Common Mistakes:

• Assuming Jenkins auto-switches ports
• Thinking Jenkins ignores port option
• Believing Jenkins starts anyway on busy port

4. You ran java -jar jenkins.war --httpPort=abc and Jenkins did not start. What is the likely cause?

medium

A. Jenkins requires root privileges to start

B. Jenkins WAR file is corrupted

C. Invalid port number format causes startup failure

D. Java is not installed on the system

Solution

1. Step 1: Analyze the port option value

   The port option --httpPort=abc uses non-numeric characters, which is invalid for a port number.

2. Step 2: Understand Jenkins port validation

   Jenkins expects a numeric port; invalid format causes startup failure with error.

3. Final Answer:

   Invalid port number format causes startup failure -> Option C

4. Quick Check:

   Port must be numeric for Jenkins to start [OK]

Hint: Port must be a number, not letters [OK]

Common Mistakes:

• Blaming Jenkins WAR file corruption
• Assuming Java is missing without checking
• Thinking root privileges are always needed

5. You want to run Jenkins WAR file on port 7070 and also specify a custom Jenkins home directory at /data/jenkins_home. Which command is correct?

hard

A. java -jar jenkins.war --httpPort=7070 --jenkinsHome=/data/jenkins_home

B. java -Djenkins.home=/data/jenkins_home -jar jenkins.war --httpPort=7070

C. java -jar jenkins.war --httpPort=7070 --jenkins.home=/data/jenkins_home

D. java -jar jenkins.war --httpPort=7070 -DjenkinsHome=/data/jenkins_home

Solution

1. Step 1: Set port option correctly

   The port is set with --httpPort=7070, which is correct syntax.

2. Step 2: Set Jenkins home directory properly

   Jenkins home is set via Java system property -Djenkins.home=path, not as a command option.

3. Step 3: Verify option correctness

   The correct command places the -Djenkins.home= option before -jar to set the system property properly.

4. Final Answer:

   java -Djenkins.home=/data/jenkins_home -jar jenkins.war --httpPort=7070 -> Option B

5. Quick Check:

   Use -Djenkins.home=PATH for custom Jenkins home [OK]

Hint: Use -Djenkins.home=PATH to set Jenkins home [OK]

Common Mistakes:

• Using --jenkinsHome or --jenkins.home as options
• Confusing Java system properties with command options
• Missing -D prefix for system properties
• Placing -D option after -jar which is incorrect