Dear Yuan, Thanks for the log file, but I’m afraid I don’t know what your Mac Ports problem is. The log file indicates a failure to fetch the archive at all. After waiting a day, did the problem go away? My workplace has lots of rules about how and when to upgrade to El Cap. As a result, I have not done it myself yet. Have you visited the Mac Ports team’s page on OS X 10.11? https://trac.macports.org/wiki/ElCapitanProblems There are no specific problems mentioning libcxx, I notice. Did you remember to re-install Mac Ports itself? If not, then problems are inevitable. Also, are Xcode and its command-line tools both updated to match the OS? If you’ve followed all the upgrade instructions and cannot install libcxx, then I think you have a Mac Ports problem and should look to that project’s issue tracker (possibly filing an issue yourself). Best wishes, Joe Fowler NIST Boulder Labs