When rebooting a fresh install of el capitan beta 2 I get the gray apple as it finds the external drive (activity LED flashes as expected) but after a short while I get the light gray circle with a line through it ( \ ) type thing indicating that the drive is not bootable. Then the mac finds my internal SSD and boots back to 10.10.4 just fine.
I had just previously been successfull in installing 10.11 b2 on an external drive to my iMac (late 2008). Able to use it fine ... until it needs to reboot for some reason (such as: it hung after several hours, or I tried to update to the beta 1.0 update, or whatever). Very clean drive (was erased in prepration for this install) - no additional apps installed on my more recent attempts. Tried the "delete iCloud Accounts directory" thing - found on the forum.
Ensured I had my 10.11 drive selected under Startup Disk preferences.
Have searched the forums and the rest of the internet to no avail.
I have repeatedly reinstalled things and retried this whole exercise.
My only work around is to completely reinstall the beta on top of what is already there. This takes about an hour each time I want to get back to playing with XCode 7 and Swift 2. This sitution is completely repeatable with a drive that doesn't even have Xcode 7 on it - just the plain beta itself (not even any updates to the beta).
Anyone else had this problem or know of any fixes?
Solved!
Once I collected all these installer components I renamed some of them to keep the order straight....
1) created a partion on my internal drive and quit trying to use an external usb drive (see release notes for beta3 at least - usb is a problem still for this beta)
2) Installed each installer in the following order
.. a) ran "Install OS X 10.11 Developer Beta.app" - supposedly this is the original beta 1 of size 6,073,615,125 bytes (Might have a different name - don't remember) - got this from the App Store (via link from developer.apple.com) which used a redemption code from my developer account.
{now booted from this beta run the following in order...}
.. b) ran "FirmwareUpdate.pkg" of size 107,597,207 - received from http://swcdn.apple.com/content/downloads/07/10/031-25506/wy6k3cd22jejq1j83kmahud7zwbaxid2z6/FirmwareUpdate.pkg - I renamed this file "FirmwareUpdate-1.pkg"
.. c) ran "FirmwareUpdate.pkg" of size 107,597,201 - received from http://swcdn.apple.com/content/downloads/45/55/031-27723/jfp6s17zwamp7zr7iwmkmdigzudq3fd72e/FirmwareUpdate.pkg - I renamed this file "FirmwareUpdate-2.pkg"
.. d) ran "RecoveryHDUpdate.pkg" of size 485,261,301 - received from http://swcdn.apple.com/content/downloads/15/54/031-25507/rjki32of9yi5zydmfv8o9v04h7s3b3vw0c/RecoveryHDUpdate.pkg
.. e) ran "OSXUpd10.11.pkg" of size 1,837,522,372 - received from http://swcdn.apple.com/content/downloads/07/10/031-25506/wy6k3cd22jejq1j83kmahud7zwbaxid2z6/OSXUpd10.11.pkg - I renamed this file "OSXUpd10.11_1-2.pkg" - its the delta fix to go from beta 1 to beta 2
.. f) ran "OSXUpd10.11.pkg"" of size 1,594,424,768 - received from http://swcdn.apple.com/content/downloads/45/55/031-27723/jfp6s17zwamp7zr7iwmkmdigzudq3fd72e/OSXUpd10.11.pkg - I renamed this file "OSXUpd10.11_2-3.pkg" - its the delta fix to go from beta 2 to beta 3
Big thanks to Max108 for all his patience, persistance, ideas and all-round help 🙂