Jenkins 1.622

Distributor ID: Ubuntu
Description: Ubuntu 14.04 LTS
Release: 14.04
Codename: trusty

When I tried to install git-plugin, caught error:
java.io.IOException: Failed to dynamically deploy this plugin
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1328)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1126)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:110)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.nio.file.AccessDeniedException: /var/lib/jenkins/plugins/git/extraRepo.html
at sun.nio.fs.UnixException.translateToIOException(UnixException.java:84)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
at sun.nio.fs.UnixFileSystemProvider.implDelete(UnixFileSystemProvider.java:244)
at sun.nio.fs.AbstractFileSystemProvider.delete(AbstractFileSystemProvider.java:103)
at java.nio.file.Files.delete(Files.java:1079)
at sun.reflect.GeneratedMethodAccessor7.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at hudson.Util.deleteFile(Util.java:247)
at hudson.Util.deleteRecursive(Util.java:310)
at hudson.Util.deleteContentsRecursive(Util.java:212)
at hudson.Util.deleteRecursive(Util.java:301)
at hudson.ClassicPluginStrategy.explode(ClassicPluginStrategy.java:524)
at hudson.ClassicPluginStrategy.createPluginWrapper(ClassicPluginStrategy.java:166)
at hudson.PluginManager.dynamicLoad(PluginManager.java:449)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1324)
... 5 more