Dual boot with Yosemite — Sierra not showing up

The result of scanning the Yosemite configuration is completely clean. More interesting, though, is this line from a scan of the Sierra volume:

/etc/sudoers, File size 2299 but expected 1563

That is potentially concerning. I do use sudo occasionally for certain Terminal operations, but I've never really dipped into this particular file from an administration standpoint.

Here's the report from Sierra (located on a local drive):

EtreCheck version: 3.0.5 (309)

Report generated 2016-09-27 10:28:26

Download EtreCheck from https://etrecheck.com

Runtime 2:12

Performance: Excellent

Click the [Support] links for help with non-Apple products.

Click the [Details] links for more information about that line.

Problem: No problem - just checking

Hardware Information:ⓘ

iMac (27-inch, Late 2012)

[Technical Specifications] - [User Guide] - [Warranty & Service]

iMac - model: iMac13,2

1 3.4 GHz Intel Core i7 CPU: 4-core

24 GB RAM Upgradeable - [Instructions]

BANK 0/DIMM0

4 GB DDR3 1600 MHz ok

BANK 1/DIMM0

4 GB DDR3 1600 MHz ok

BANK 0/DIMM1

8 GB DDR3 1600 MHz ok

BANK 1/DIMM1

8 GB DDR3 1600 MHz ok

Bluetooth: Good - Handoff/Airdrop2 supported

Wireless: en1: 802.11 a/b/g/n

Video Information:ⓘ

NVIDIA GeForce GTX 680MX - VRAM: 2048 MB

iMac 2560 x 1440

System Software:ⓘ

macOS Sierra 10.12 (16A323) - Time since boot: less than an hour

Disk Information:ⓘ

APPLE HDD ST1000DM003 disk1 : (1 TB) (Rotational)

EFI (disk1s1) <not mounted> : 210 MB

Recovery HD (disk1s3) <not mounted> [Recovery]: 650 MB

Office iMac (disk2) / : 1.11 TB (320.13 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 998.70 GB Online

APPLE SSD SM128E disk0 : (121.33 GB) (Solid State - TRIM: Yes)

EFI (disk0s1) <not mounted> : 210 MB

Boot OS X (disk0s3) <not mounted> : 134 MB

Office iMac (disk2) / : 1.11 TB (320.13 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 998.70 GB Online

USB Information:ⓘ

Apple Inc. FaceTime HD Camera (Built-in)

Apple Inc. BRCM20702 Hub

Apple Inc. Bluetooth USB Host Controller

Western Digital My Passport 0820

Seagate Backup+ Desk

SanDisk U3 Cruzer Micro

Datacolor Datacolor Spyder4

Firewire Information:ⓘ

Seagate Backup+ Desk Mac 800mbit - 800mbit max

disk3s1 (disk3s1) <not mounted> : 210 MB

Media (Yosemite) (disk3s2) /Volumes/Media (Yosemite) : 3.00 TB (2.35 TB free)

Recovery HD (disk3s3) <not mounted> [Recovery]: 650 MB

Thunderbolt Information:ⓘ

Apple Inc. thunderbolt_bus

Apple Inc. Thunderbolt to FireWire Adapter

Configuration files:ⓘ

/etc/sudoers, File size 2299 but expected 1563

Gatekeeper:ⓘ

Mac App Store and identified developers

Kernel Extensions:ⓘ

/Library/Extensions

[loaded] com.Cycling74.driver.Soundflower (2.0b2 - SDK 10.10 - 2016-09-22) [Support]

[loaded] com.seagate.driver.PowSecDriverCore (5.2.7 (26979) - SDK 10.4 - 2016-09-22) [Support]

/Library/Extensions/Seagate Storage Driver.kext/Contents/PlugIns

[not loaded] com.seagate.driver.PowSecLeafDriver_10_4 (5.2.7 (26979) - SDK 10.4 - 2015-07-16) [Support]

[loaded] com.seagate.driver.PowSecLeafDriver_10_5 (5.2.7 (26979) - SDK 10.5 - 2015-07-16) [Support]

[not loaded] com.seagate.driver.SeagateDriveIcons (5.2.7 (26979) - SDK 10.4 - 2015-07-16) [Support]

System Launch Agents:ⓘ

[not loaded] 7 Apple tasks

[loaded] 175 Apple tasks

[running] 89 Apple tasks

System Launch Daemons:ⓘ

[not loaded] com.apple.jetsamproperties.Mac.plist (2016-08-25) [Support]

[not loaded] 37 Apple tasks

[loaded] 167 Apple tasks

[running] 100 Apple tasks

Launch Agents:ⓘ

[running] com.canon.MFManager.plist (2012-05-22) [Support]

[loaded] com.oracle.java.Java-Updater.plist (2013-06-07) [Support]

Launch Daemons:ⓘ

[loaded] com.adobe.fpsaud.plist (2016-08-29) [Support]

[loaded] com.apple.aelwriter.plist (2010-05-18)

[loaded] com.barebones.authd.plist (2012-05-19) [Support]

[not loaded] com.barebones.textwrangler.plist (2011-03-04) [Support]

[loaded] com.oracle.java.Helper-Tool.plist (2013-06-07) [Support]

[running] com.seagate.TBDecorator.plist (2013-10-11) [Support]

User Launch Agents:ⓘ

[loaded] com.apple.MobileMeSyncClientAgent.plist (2011-08-07)

[loaded] com.apple.SafariBookmarksSyncer.plist (2010-02-05)

[loaded] com.bittorrent.uTorrent.plist (2016-09-20)

[loaded] com.google.keystone.agent.plist (2016-07-12) [Support]

[not loaded] jp.co.canon.Inkjet_Extended_Survey_Agent.plist (2009-08-30) [Support]

User Login Items:ⓘ

Google Drive Application (/Applications/Google Drive.app)

Dropbox Application (/Applications/Dropbox.app)

SpyderUtility Application (/Applications/Datacolor/Spyder4Pro/Support/SpyderUtility.app)

Internet Plug-ins:ⓘ

JavaAppletPlugin (1.7.13.20): Java 7 Update 13 (2013-06-07) [Support]

SpeedDownload Browser Plugin: 2.1.2 (2013-06-07) [Support]

Flip4Mac WMV Plugin: 3.2.0.16 - SDK 10.8 (2013-06-07) [Support]

RealPlayer Plugin: Unknown (2013-06-07) [Support]

Silverlight: 5.1.30514.0 - SDK 10.6 (2015-04-24) [Support]

FlashPlayer-10.6: 23.0.0.162 - SDK 10.9 (2016-09-19) [Support]

QuickTime Plugin: 7.7.3 (2016-09-13)

Flash Player: 23.0.0.162 - SDK 10.9 (2016-09-19) [Support]

iPhotoPhotocast: 7.0 (2013-06-07)

AdobePDFViewer: 9.0.0 (2014-07-14) [Support]

EPPEX Plugin: 3.0.5.0 (2013-06-07) [Support]

JavaAppletPlugin: Java 8 Update 101 build 13 (2016-08-26) Check version

User internet Plug-ins:ⓘ

CitrixOnlineWebDeploymentPlugin: 1.0.104 (2013-04-11) [Support]

fbplugin_1_0_3: Unknown (2010-02-25) [Support]

WebEx64: 1.0 - SDK 10.6 (2012-10-29) [Support]

Safari Extensions:ⓘ

MacShop - Ivo Nedelko - http://macshopp.com (2014-10-08)

SaveFrom.net helper - SaveFrom.net - http://savefrom.net (2015-09-28)

3rd Party Preference Panes:ⓘ

A Better Finder Preferences (2009-02-14) [Support]

Flash Player (2016-08-29) [Support]

Flip4Mac WMV (2013-06-07) [Support]

Java (2016-08-26) [Support]

Perian (2013-06-07) [Support]

Seagate Dashboard for Mac OSX (2015-08-31) [Support]

Time Machine:ⓘ

Skip System Files: NO

Mobile backups: OFF

Auto backup: YES

Volumes being backed up:

Office iMac: Disk size: 1.11 TB Disk used: 791.05 GB

Media (Yosemite): Disk size: 3.00 TB Disk used: 645.40 GB

Destinations:

Time Machine [Local]

Total size: 5.00 TB

Total number of backups: 137

Oldest backup: 6/4/14, 8:10 AM

Last backup: 9/27/16, 10:01 AM

Size of backup disk: Adequate

Backup size 5.00 TB > (Disk used 1.44 TB X 3)

Top Processes by CPU:ⓘ

3% fontd

2% WindowServer

1% kernel_task

0% launchd

0% com.apple.AmbientDisplayAgent

Top Processes by Memory:ⓘ

1.23 GB kernel_task

492 MB mds_stores

492 MB mdworker(15)

295 MB Google Drive

221 MB Dropbox

Virtual Memory Information:ⓘ

18.00 GB Free RAM

5.96 GB Used RAM (2.62 GB Cached)

0 B Swap Used

Diagnostics Information:ⓘ

Sep 27, 2016, 10:23:57 AM Self test - passed

Sep 25, 2016, 10:01:33 AM /Library/Logs/DiagnosticReports/com.boinx.fmexport_2016-09-25-100133_[redacted] .cpu_resource.diag [Details]

/Applications/FotoMagico.localized/FotoMagico.app/Contents/XPCServices/com.boin x.fmexport.xpc/Contents/MacOS/com.boinx.fmexport

Sep 25, 2016, 09:41:46 AM /Library/Logs/DiagnosticReports/com.boinx.fmexport_2016-09-25-094146_[redacted] .cpu_resource.diag [Details]

Sep 24, 2016, 01:04:43 PM /Library/Logs/DiagnosticReports/FotoMagico_2016-09-24-130443_[redacted].cpu_res ource.diag [Details]

/Applications/FotoMagico.localized/FotoMagico.app/Contents/MacOS/FotoMagico

And here's the report from Yosemite (located on a remote drive):

EtreCheck version: 3.0.5 (309)

Report generated 2016-09-27 10:19:40

Download EtreCheck from https://etrecheck.com

Runtime 2:54

Performance: Excellent

Click the [Support] links for help with non-Apple products.

Click the [Details] links for more information about that line.

Problem: No problem - just checking

Hardware Information:ⓘ

iMac (27-inch, Late 2012)

[Technical Specifications] - [User Guide] - [Warranty & Service]

iMac - model: iMac13,2

1 3.4 GHz Intel Core i7 CPU: 4-core

24 GB RAM Upgradeable - [Instructions]

BANK 0/DIMM0

4 GB DDR3 1600 MHz ok

BANK 1/DIMM0

4 GB DDR3 1600 MHz ok

BANK 0/DIMM1

8 GB DDR3 1600 MHz ok

BANK 1/DIMM1

8 GB DDR3 1600 MHz ok

Bluetooth: Good - Handoff/Airdrop2 supported

Wireless: en1: 802.11 a/b/g/n

Video Information:ⓘ

NVIDIA GeForce GTX 680MX - VRAM: 2048 MB

iMac 2560 x 1440

System Software:ⓘ

OS X Yosemite 10.10.5 (14F1912) - Time since boot: less than an hour

Disk Information:ⓘ

APPLE HDD ST1000DM003 disk1 : (1 TB) (Rotational)

EFI (disk1s1) <not mounted> : 210 MB

Recovery HD (disk1s3) <not mounted> [Recovery]: 650 MB

Office iMac (disk2) /Volumes/Office iMac : 1.11 TB (320.40 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 998.70 GB Online

APPLE SSD SM128E disk0 : (121.33 GB) (Solid State - TRIM: Yes)

EFI (disk0s1) <not mounted> : 210 MB

Boot OS X (disk0s3) <not mounted> : 134 MB

Office iMac (disk2) /Volumes/Office iMac : 1.11 TB (320.40 GB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 998.70 GB Online

USB Information:ⓘ

Western Digital My Passport 0820 2 TB

EFI (disk6s1) <not mounted> : 210 MB

Tape Archives (disk6s2) /Volumes/Tape Archives : 1.50 TB (596.93 GB free)

Recovery HD (disk6s3) <not mounted> [Recovery]: 650 MB

Install OS X Yosemite (disk6s4) /Volumes/Install OS X Yosemite : 502.14 GB (495.76 GB free)

Seagate Backup+ Desk 5 TB

EFI (disk5s1) <not mounted> : 315 MB

Time Machine (disk5s2) /Volumes/Time Machine : 5.00 TB (687.38 GB free)

Datacolor Datacolor Spyder4

Apple Inc. FaceTime HD Camera (Built-in)

SanDisk U3 Cruzer Micro 8.04 GB

Shuttle (disk4s1) /Volumes/Shuttle : 8.04 GB (1.47 GB free)

Apple Inc. BRCM20702 Hub

Apple Inc. Bluetooth USB Host Controller

Firewire Information:ⓘ

Seagate Backup+ Desk Mac 800mbit - 800mbit max

disk3s1 (disk3s1) <not mounted> : 210 MB

Media (Yosemite) (disk3s2) / : 3.00 TB (2.35 TB free)

Recovery HD (disk3s3) <not mounted> [Recovery]: 650 MB

Thunderbolt Information:ⓘ

Apple Inc. thunderbolt_bus

Apple Inc. Thunderbolt to FireWire Adapter

Gatekeeper:ⓘ

Mac App Store and identified developers

System Launch Agents:ⓘ

[not loaded] 4 Apple tasks

[loaded] 147 Apple tasks

[running] 61 Apple tasks

System Launch Daemons:ⓘ

[not loaded] 42 Apple tasks

[loaded] 140 Apple tasks

[running] 79 Apple tasks

Launch Daemons:ⓘ

[loaded] com.adobe.fpsaud.plist (2016-08-29) [Support]

User Launch Agents:ⓘ

[loaded] com.google.keystone.agent.plist (2016-07-20) [Support]

User Login Items:ⓘ

iTunesHelper Application Hidden (/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)

Dropbox Application (/Volumes/Office iMac/Applications/Dropbox.app)

Google Drive Application (/Volumes/Office iMac/Applications/Google Drive.app)

SpyderUtility Application (/Volumes/Office iMac/Applications/Datacolor/Spyder4Pro/Support/SpyderUtility.app)

Internet Plug-ins:ⓘ

FlashPlayer-10.6: 23.0.0.162 - SDK 10.9 (2016-09-16) [Support]

QuickTime Plugin: 7.7.3 (2016-09-16)

Flash Player: 23.0.0.162 - SDK 10.9 (2016-09-16) [Support]

Default Browser: 600 - SDK 10.10 (2015-07-16)

3rd Party Preference Panes:ⓘ

Flash Player (2016-08-29) [Support]

Time Machine:ⓘ

Skip System Files: NO

Mobile backups: OFF

Auto backup: YES

Volumes being backed up:

Tape Archives: Disk size: 1.50 TB Disk used: 900.30 GB

Media (Yosemite): Disk size: 3.00 TB Disk used: 645.69 GB

Destinations:

Time Machine [Local]

Total size: 5.00 TB

Total number of backups: 134

Oldest backup: 6/4/14, 8:10 AM

Last backup: 9/18/16, 11:09 AM

Size of backup disk: Adequate

Backup size 5.00 TB > (Disk used 1.55 TB X 3)

Top Processes by CPU:ⓘ

2% kernel_task

2% WindowServer

2% fontd

1% identityservicesd

1% mds

Top Processes by Memory:ⓘ

1.06 GB kernel_task

541 MB mds_stores

270 MB Google Drive

172 MB Dropbox

74 MB iconservicesagent(2)

Virtual Memory Information:ⓘ

20.00 GB Free RAM

4.49 GB Used RAM (2.12 GB Cached)

0 B Swap Used

Diagnostics Information:ⓘ

Sep 27, 2016, 10:14:20 AM Self test - passed

After a couple of days testing across several clean installs of Sierra, El Capitan, and Yosemite across multiple hard drives (though, not, multiple computers) I've narrowed down the problem to a very specific configuration. When Sierra is installed on the first volume of an internal Fusion Drive, Yosemite will not offer this volume as a restart option in the Startup Disk preference panel. All other combinations work fine — Sierra as the second volume, El Cap or Yosemite on the first volume, etc... So it would appear that there is an issue with Sierra on a Fusion Drive that prevents Yosemite on an external drive from seeing it as a viable boot option.

I spent a couple of hours on the phone with Apple yesterday going through various configurations and — at least on my class of iMac (27" late 2012) — it's a repeatable problem, and a bug has been filed.

The problem definitely does not occur when a Fusion Drive is not present and it may not be present on other mac models.

This is where it may be model specific. I ran a fairly exhaustive set of tests with clean installs of Sierra, El Capitan, and Yosemite in one and two partition internal configurations, with four clean installs on external drives. With each configuration I would boot to a particular volume, then check to verify that each bootable volume showed up in Startup Disks. The only time a bootable volume failed to appear in Startup Disks was from Yosemite when Sierra was installed on volume one of the Fusion Drive.

To further prove this to myself, I unlinked the Fusion Drive (which I really don't advise!) so I could treat my internal drive as a plain old hard drive and an SSD. When I did so I was actually able to create 4 partitions (normally, 2 is the limit on a Fusion Drive), installing a different OS on each. Here, again, only when Sierra was on what the OS believed to be the first volume was Yosemite not able to "see" Sierra from Startup Disks — though it was able to see a second Sierra boot volume on another partition.