Below is the error when we tried to access the jenkins server on 8080 port

VERSION :  Jenkins ver. 2.205

com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.security.GlobalMatrixAuthorizationStrategy at com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:79) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:55) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:79) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:74) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.SecurityMapper.realClass(SecurityMapper.java:71) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at hudson.util.XStream2$CompatibilityMapper.realClass(XStream2.java:380) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at hudson.util.xstream.MapperDelegate.realClass(MapperDelegate.java:43) at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30) at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:48) at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:458) at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:324) Caused: jenkins.util.xstream.CriticalXStreamException: hudson.security.GlobalMatrixAuthorizationStrategy : hudson.security.GlobalMatrixAuthorizationStrategy ---- Debugging information ---- message : hudson.security.GlobalMatrixAuthorizationStrategy cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException cause-message : hudson.security.GlobalMatrixAuthorizationStrategy class : hudson.model.Hudson required-type : hudson.model.Hudson converter-type : hudson.util.RobustReflectionConverter path : /hudson/authorizationStrategy line number : 12 version : not available ------------------------------- at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:353) at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:267) at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72) at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65) at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66) at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50) at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134) at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32) at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1189) at hudson.util.XStream2.unmarshal(XStream2.java:162) at hudson.util.XStream2.unmarshal(XStream2.java:133) at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1173) at hudson.XmlFile.unmarshal(XmlFile.java:180) Caused: java.io.IOException: Unable to read /var/lib/jenkins/config.xml at hudson.XmlFile.unmarshal(XmlFile.java:183) at hudson.XmlFile.unmarshal(XmlFile.java:163) at jenkins.model.Jenkins.loadConfig(Jenkins.java:3102) at jenkins.model.Jenkins.access$1200(Jenkins.java:315) at jenkins.model.Jenkins$13.run(Jenkins.java:3203) at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169) at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296) at jenkins.model.Jenkins$5.runTask(Jenkins.java:1142) at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214) at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused: org.jvnet.hudson.reactor.ReactorException at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:282) at jenkins.InitReactorRunner.run(InitReactorRunner.java:48) at jenkins.model.Jenkins.executeReactor(Jenkins.java:1175) at jenkins.model.Jenkins.<init>(Jenkins.java:965) at hudson.model.Hudson.<init>(Hudson.java:85) at hudson.model.Hudson.<init>(Hudson.java:81) at hudson.WebAppMain$3.run(WebAppMain.java:233) Caused: hudson.util.HudsonFailedToLoad at hudson.WebAppMain$3.run(WebAppMain.java:250)