title: What actually is $RPM_BUILD_ROOT?
body: <p>In the process of building an RPM package, I have to specify the BuildRoot and later will be used in %install which invovles $RPM_BUILD_ROOT. I always think that $RPM_BUILD_ROOT is the fake installation for RPM to perform packaging. Then, at install time using the RPM package, it will install into actual location. For example:</p>
  
  <pre><code>$RPM_BUILD_ROOT/usr/bin
  </code></pre>
  
  <p>I thought that $RPM_BUILD_ROOT is for the packaging process only, and in some ways RPM can distinguish the $RPM_BUILD_ROOT and the actual install location when the user performs "rpm -ivh package.rpm" will be /usr/bin.</p>
  
  <p>But recently upon reading some documents, it is suggested that $RPM_BUILD_ROOT is the actual location which will be installed, and the $RPM_BUILD_ROOT is specified by user with the setting of environment variable $RPM_BUILD_ROOT in order to let the users install the package in their desire locations. Otherwise, $RPM_BUILD_ROOT will be null and it will install into the default location. In the above case, it is /usr/bin . Thus, $RPM_BUILD_ROOT is not just for packaging or "fake installation" process, but is a way for user to define install location, similar to select folder location in Windows.</p>
  
  <p>I don't know my thinking is correct or not. Can someone please verify? Thanks in advance.</p>