I thought of posting both the question and the answer for others' knowledge. I deployed a large EAR (contained more than ~1024 jars/wars) on JBoss running with Java 6 on Linux, and the deployment process cried throwing the following exception: java.lang.RuntimeException: java.util.zip.ZipException: error in opening zip file) at org.jboss.deployment.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:53) at org.jboss.deployment.MainDeployer.init(MainDeployer.java:901) at org.jboss.deployment.MainDeployer.init(MainDeployer.java:895) at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:809) at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:782) .... Caused by: java.lang.RuntimeException: java.util.zip.ZipException: error in opening zip file at org.jboss.util.file.JarArchiveBrowser.<init>(JarArchiveBrowser.java:74) at org.jboss.util.file.FileProtocolArchiveBrowserFactory.create(FileProtocolArchiveBrowserFactory.java:48) at org.jboss.util.file.ArchiveBrowser.getBrowser(ArchiveBrowser.java:57) at org.jboss.ejb3.EJB3Deployer.hasEjbAnnotation(EJB3Deployer.java:213) .... This was caused by the 'limit of number of open file descriptors' of Linux/Unix operating systems. The default is 1024. You can check the default value using: ulimit -n To increase the number of open file descriptors (say to 2048): ulimit -n 2048 Check the man page of ulimit for more details.