[...]
> > I think I have the full story now.
> >
> > When you click the "Get" button on the El Capitan page, App Store
> > fetches a preflight package from Apple's servers. The same script is
> > delivered on all Mac models and all OS versions.
> >
> > (This mechanism does not apply to re-downloading El Capitan from the
> > Purchased list.)
> >
> > App Store runs a script in the package which does model checks: it goes
> > through the same tests as the El Capitan installer, so your Mac must
> > meet the system requirements for El Capitan in order to do the download.
> > You also must be running 10.6.8 or later, and not 10.12 or later.
> >
> > Here is the interesting bit.
> >
> > The script run by App Store does an additional test which is NOT part of
> > the El Capitan installer. The Mac trying to get El Capitan must pass one
> > of these additional tests:
> >
> > (a) A 2007-2009 Mac model which is supported by El Capitan but not
> > supported by later OS versions; or
> >
> > (b) Any Mac model supported by El Capitan which is currently running Mac
> > OS X 10.6.8 through 10.7.5.
> >
> > If your Mac passes either of those tests, the El Capitan installer is
> > downloaded.
> >
> > If your Mac is a Late 2009 or newer model currently running OS X 10.8
> > through 10.11.6, you get the error message saying "OS X 10.11 cannot be
> > installed on this computer." and the installer is not downloaded.
[...]
> David, this is very interesting but a bit beyond my understanding
I posted that mostly for the benefit of those who were wondering about
the technical details and to correct some points from earlier in the
thread (including some of my own, as I was not previously aware that
Apple had restricted the ability to get the El Capitan installer, and I
was working with incomplete information).
The important bit in your case was the explanation of why you were not
able to get El Capitan, which is summarised in the last paragraph I've
left quoted above from my previous post.
> (pre-flight?)
That's what Apple calls it (it is a file with the extension ".pfpkg" -
I'm assuming the "pf" is short for "pre-flight").
A "package" is a file format Apple uses to distribute software, which
among other things contains files to be installed, and scripts which
contain instructions to do tests, present information to the user, pick
the appropriate files, etc.
Before App Store actually downloads the El Capitan installer, it
downloads a package to test whether to allow the main download to
proceed.
The "flight" in this case alludes to the download of the OS: data is "in
flight" when travelling between server and client. A "pre-flight
package" is a package which comes before the "flight" to test whether it
is allowed to "take off".
> but I'm glad you figured it out. I never was able to dl a
> copy of El Capitan, and installed Sierra instead. But I do have the
> installer DVD that I alluded to above sitting in my desk drawer now.
> Maybe I should open it up just to see what kind of info I can glean
> from it (build number, date, whatever).
Assuming that DVD is the standard bootable installer, you should see
nothing on it apart from an "Install OS X El Capitan" application.
There is also a bootable system but it is hidden.
You can easily find the version number by doing a Get Info on the DVD
icon (or if you have opened the window showing the content of the DVD,
click on the empty background of the window so no file is selected, then
use Get Info). Look for the Version field, which will say something like
10.11.6.
The build version is not as easy to locate, and is usually of limited
interest except to rule out odd cases like a model-specific variant. It
can be found if you navigate to this folder:
/Volumes/[name of DVD]/System/Library/CoreServices
e.g. using the Finder "Go to Folder" command or Terminal, then view the
text file SystemVersion.plist and look for this bit:
<key>ProductBuildVersion</key>
<string>15G31</string>
The build version is the second of those lines, between the <string> and
</string> delimiters.
If you had been able to download the El Capitan installer, the current
release is version 10.11.6 with a build version of 15G1011.
The original public releases (courtesy of MacTracker) were:
10.11 15A284 September 30, 2015
10.11.1 15B42 October 21, 2015
10.11.2 15C50 December 8, 2015
10.11.3 15D21 January 19, 2016
10.11.4 15E65 March 21, 2016
10.11.5 15F34 May 16, 2016
10.11.6 15G31 July 18, 2016
--
David Empson
dem...@actrix.gen.nz