title: hudson.model.UpdateCenter#updateDefaultSite: Upgrading Jenkins. Failed to update the default Update Site 'default'. Plugin upgrades may fail
body: <p>How do I start the Jenkins process in offline mode on one of my servers?</p>
  <p>I am trying to start Jenkins by running command java -jar jenkins.war, but it is failing at the below warning because of no connectivity.</p>
  <p>Is there any way to skip this plugin upgrade through the internet and bring the Jenkins up and running?</p>
  <pre><code>2021-04-27 16:53:43.490+0000 [id=64]    WARNING hudson.model.UpdateCenter#updateDefaultSite: Upgrading Jenkins. Failed to update the default Update Site 'default'. Plugin upgrades may fail.
  2021-04-27 16:53:43.490+0000 [id=64]    WARNING hudson.model.UpdateCenter#updateDefaultSite: Upgrading Jenkins. Failed to update the default Update Site 'default'. Plugin upgrades may fail.
  java.net.SocketTimeoutException: connect timed out
          at java.net.PlainSocketImpl.socketConnect(Native Method)
          at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
          at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
          at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
          at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
          at java.net.Socket.connect(Socket.java:607)
          at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:666)
          at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
          at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
          at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
          at sun.net.www.protocol.https.HttpsClient.&lt;init&gt;(HttpsClient.java:264)
          at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367)
          at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
          at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
          at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
          at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
          at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1570)
          at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
          at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:268)
          at hudson.model.DownloadService.loadJSON(DownloadService.java:116)
          at hudson.model.UpdateSite.updateDirectlyNow(UpdateSite.java:218)
          at hudson.model.UpdateSite.updateDirectlyNow(UpdateSite.java:213)
          at hudson.model.UpdateCenter.updateDefaultSite(UpdateCenter.java:2611)
          at jenkins.install.SetupWizard.init(SetupWizard.java:212)
          at jenkins.install.InstallState$InitialSecuritySetup.initializeState(InstallState.java:168)
          at jenkins.model.Jenkins.setInstallState(Jenkins.java:1104)
          at jenkins.install.InstallUtil.proceedToNextStateFrom(InstallUtil.java:98)
          at jenkins.install.InstallState$Unknown.initializeState(InstallState.java:86)
          at jenkins.model.Jenkins$16.run(Jenkins.java:3356)
          at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
          at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
          at jenkins.model.Jenkins$5.runTask(Jenkins.java:1131)
          at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
          at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
          at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:68)
          at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
          at java.lang.Thread.run(Thread.java:748)
  2021-04-27 16:53:43.491+0000 [id=53]    INFO    jenkins.InitReactorRunner$1#onAttained: Completed initialization
  2021-04-27 16:53:43.494+0000 [id=92]    INFO    hudson.util.Retrier#start: The attempt #1 to do the action check updates server failed with an allowed exception:
  java.net.SocketTimeoutException: connect timed out
          at java.net.PlainSocketImpl.socketConnect(Native Method)
          at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
          at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
          at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
          at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
          at java.net.Socket.connect(Socket.java:607)
          at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:666)
          at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
          at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
          at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
          at sun.net.www.protocol.https.HttpsClient.&lt;init&gt;(HttpsClient.java:264)
          at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367)
          at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191)
          at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
          at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
          at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
          at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1570)
          at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
          at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:268)
          at hudson.model.DownloadService.loadJSON(DownloadService.java:116)
          at hudson.model.UpdateSite.updateDirectlyNow(UpdateSite.java:218)
          at hudson.model.UpdateSite.updateDirectlyNow(UpdateSite.java:213)
          at hudson.PluginManager.checkUpdatesServer(PluginManager.java:1882)
          at hudson.util.Retrier.start(Retrier.java:63)
          at hudson.PluginManager.doCheckUpdatesServer(PluginManager.java:1853)
          at jenkins.DailyCheck.execute(DailyCheck.java:93)
          at hudson.model.AsyncPeriodicWork.lambda$doRun$0(AsyncPeriodicWork.java:100)
          at java.lang.Thread.run(Thread.java:748)
  2021-04-27 16:53:43.494+0000 [id=92]    INFO    hudson.util.Retrier#start: Calling the listener of the allowed exception 'connect timed out' at the attempt #1 to do the action check updates server
  2021-04-27 16:53:43.497+0000 [id=92]    INFO    hudson.util.Retrier#start: Attempted the action check updates server for 1 time(s) with no success
  2021-04-27 16:53:43.499+0000 [id=92]    SEVERE  hudson.PluginManager#doCheckUpdatesServer: Error checking update sites for 1 attempt(s). Last exception was: SocketTimeoutException: connect timed out
  2021-04-27 16:53:43.504+0000 [id=36]    INFO    hudson.WebAppMain$3#run: Jenkins is fully up and running
  2021-04-27 16:53:43.504+0000 [id=92]    INFO    hudson.model.AsyncPeriodicWork#lambda$doRun$0: Finished Download metadata. 20,249 ms
  2021-04-27 16:54:13.279+0000 [id=106]   INFO    hudson.model.AsyncPeriodicWork#lambda$doRun$0: Started Periodic background build discarder
  2021-04-27 16:54:13.280+0000 [id=106]   INFO    hudson.model.AsyncPeriodicWork#lambda$doRun$0: Finished Periodic background build discarder. 1 ms```
  
  </code></pre>