Hi Uwe, are you certain that jenkins started the firefox process? From what I see in your example output parent process of the firefox process has PID 31323, whilst maven/java processes have PID 31236 and 31202.

DISPLAY environment variable should be set in all processes started by the jenkins job, even in the ones started by "Invoke top-level Maven targets". You can check this with exec-maven-plugin, i.e.:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>freestyle</groupId>
   <artifactId>sample</artifactId>
   <packaging>jar</packaging>
   <version>1.0.0-SNAPSHOT</version>
   <build>
      <plugins>
         <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.2.1</version>
            <executions>
               <execution>
                  <id>show-display</id>
                  <phase>compile</phase>
                  <goals>
                     <goal>exec</goal>
                  </goals>
                  <configuration>
                     <executable>env</executable>
                  </configuration>
               </execution>
            </executions>
         </plugin>
      </plugins>
   </build>
</project>

Thank you for the helpful code snippet! It turns out that we were a little overeager in making sure that all processes started as jenkins get the same environment. The DISPLAY variable was set in all of _/.profile, /.bash_profile and ~/.bashrc. The Xvfb plugin works fine.

Unfortunately, that's not entirely true. When a DISPLAY variable already exists in the environment of the slave, the plugin will overwrite it with the correct value in a "Execute shell" build step, but it will NOT overwrite it in a "Invoke Maven" build stop.

I verified that the xvfb plugin actually changes the DISPLAY entry in the EnvVars map, but it seems the Maven build step changes it back later. Although looking at the source code, I can not find where it does that.

I'm not sure if this really is a bug with this plugin, or with Jenkins Maven build step, as the plugin seems to do the right thing.

Hi Marc, can you provide a test scenario for the problem you're experiencing? As I wrote in the previous comment, to me it seems that when Invoke Maven command is performed in freestyle build, DISPLAY is set correctly regardless of it being set in the environment of the process tree or not. I.e. my setup has DISPLAY variable set (I'm running in GUI mode), so when I start jenkins it inherits DISPLAY from my GUI enviroment, and the POM above and with Invoke Maven step on freestyle projects yields the Xvfb DISPLAY opened by the plugin.

I was using your pom.xml from above. I created a freestyle job, with two buildsteps, a shell which executes mvn and a Maven buildstep doing the same. I get the correct output from the shell build step, and the wrong output from the other.

Maybe the important point is, that the DISPLAY variable has to exist in the environment of the slave (we are using swarm) and not the master?

Still no way given to reproduce this issue, and original submitter confirmed that the DISPLAY was set externally. Closing.

Closing resloved issues

As this is a different problem from the original report, I created a separate ticket with steps to reproduce: JENKINS-19950