On Jenkins configuration page in section \"Jenkins URL\" I\'ve set this option to \"http://name_of_my_machine.jenkins:8080/\" Usually I open jenkins by: \"http://localhost:8
Jenkins can't determine its URL on its own. So when it needs to create full links that's where the URL is taken from. In general even if you specify the wrong URL it should not affect the way Jenkins works in any significant way. It certainly has no effect on the URL that you enter in your browser to connect to Jenkins server. You can either specify http://localhost:8080
(when connecting from your machine and assuming that you started Jenkins on port 8080) or http://<machine_hostname>:8080
when connecting from anywhere.
So no matter what you specify it has no effect on connecting to Jenkins, therefore http://name_of_my_machine.jenkins:8080/
won't work, as .jenkins
is not part of the name (e.g. ping name_of_my_machine.jenkins
won't find the host).
Whenever Jenkins needs to create a URL that points to itself, Jenkins picks it up from the "Jenkins URL" setting in the global configuration.
Jenkins could try to guess the URL by e.g. getting the hostname and combining that with the port it is running on. But sometimes the hostname is not the same as the DNS name. And what if you have placed a front-end or proxy before Jenkins that e.g. terminates SSL connections and you would really like people to use Jenkins at https://company.com/jenkins/. Jenkins running in port 8080 cannot know about the front-end. The only reliable way for Jenkins to get the URL to itself is for an administrator setting it in Jenkins configuration.
Jenkins needs to know it's own URL when it is creating links that point back to itself. It does this e.g. when it sends out emails containing direct links to build results. Also, if you have a JNLP type slave, the slave initiates the connection to the master and the master returns a message which contains a link back to Jenkins for downloading the slave agent software.
Do you mean the option in the E-mail configuration section? This is only to generate the links in emails Jenkins sends (see the help for the option -- click the symbol with the question mark). If after changing it you cannot access your server anymore, it must be something else.