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About OS X 10.11 "El Capitan"

With the of macOS 10.14 in September 2018 macOS 10.11 ("El Capitan") became unsupported.

macOS 10.11 is considered insecure and not suited for use in a professional context!

If your Mac still runs a macOS version below 10.15 you should upgrade to a supported version of macOS as soon as possible!

The information below is for historical reference only.

Mac OS X 10.11 became available from the Mac App Store on September 30th, 2015. It has been superseeded by macOS 10.12 Sierra on September 20th, 2016. Apple has published a list of 68 vulnerabilities in OS X 10.11.6 for which there is no security update other than 10.12 Sierra.

With the release of macOS 10.14 in September 2018 Mac OS X 10.11 is considered obsolete and unsupported.

The information below is only for historical reference!

There are three important actions to take before you install it:

  • Ensure that all the software you are using is compatible with it. See below for a list of known issues.
  • Verify your hard-disk or SSD before doing the install.
  • Make sure you have a recent backup, allowing you to recover your data in case of problems.

Known Issues

This is a summary of issues known so far. Please note that this list is by no means complete. Please contact the Service Desk if you encounter a problem with an application or a service.


Using Network Groups from Active Directory (egroups in CERN speak) does not work out of the box. To be able to use Network Groups from Active Directory you have to increase the timeout for replies from the server, otherwise the request will fail and the user can not log in. To increase the timeout you should run

sudo /usr/libexec/PlistBuddy -c "Set :Modules:SystemCache:Membership\ Query\ Timeout\ in\ Seconds 20" /Library/Preferences/OpenDirectory/opendirectoryd.plist

Please note that this is only needed if you want to enable network groups from AD - if you enable individual AD accounts this is not needed. does not sync .ics calendar entries (like the ones from Indico) to the exchange server. The entry for such events will appear in the calendar on the device where you imported it, but it will not be synchronised to other devices via your exchange account.

Two possible workaround for the issue have been found:

  • The "duplicate/delete" workaround:
  • Import the event.ics file into your exchange calendar
  • Duplicate the event
  • Delete the original event
  • The "move between calendars" workaround:
  • Import the event.ics file into one of your exchange calendars
  • Move th eevent to one of your local calendars
  • Move the event to one of your exchange calendars

After step 3 the event will be synced. Step one is needed, you can not skip it :(


Previous versions of MacPorts are not compatible with OS X 10.11, according to MacPorts needs to be reinstalled.

  • Adding multiple exchange accounts requires prepending "CERN\" to the email-address. Without the prepended "CERN\" you will get the mesage "The account exists already".
  • We get occassional reports about stopping to fetch new messages. We don't have the impression that the frequency of this is higher than with previous versions of But at least re-creating a deleted account appears to be much faster than with previous versions of

Office 2016

In the early days some users reported app crashes when running Office 2016 under OS X 10.11. I some cases the activation got lost and needed to be restored. This issue appears to be solved.


The previous openAFS client does not work under 10.11, it is recommened to uninstall it before upgrading to 10.11.

A working client is announced on, please read the description carefully before installing the client.

Outlook 2011

Outlook 2011 versions below 14.5.6 hang when connecting a mail server. Outlook users should update at least to 14.5.6 before migrating to OS X 10.11.

Symantec Endpoint Protection is not compatible

It is recommened to uninstall it before upgrading to 10.11.


It is recommended to use XQuartz 2.7.9 or later ( XQuartz installs into /opt/X11 now, and creates symlinks in /usr. If you have one of the previous versions of XQuartz that did install in /usr, the symlink /usr/X11 -> /opt/X11 cannot be installed, and some X programs will not start. In that case you have to remove the directory /usr/X11 and manually create the symlink.

Due to recent changes to X11 libs on the Linux side there are problems with the actual production version of XQuartz, please see for a possible work-around.