MacOS – Clean Install, or in-place upgrade from Mountain Lion to Yosemite

installmacosupgrade

In the old days, doing a clean install was pretty much required for a major Mac OS X 10.x release. Is that still the case? Or should this graybeard let go of his old ways?

The MacBook in question works well. The hard disk gets high marks from Disk Utility app checks. Both a Time Machine and a full clone of the disk will be in place, each on their own external hard disk.

Going from Mountain Lion to Yosemite in this upgrade. Should I try simply running the Yosemite installer as being suggested by the App Store app?

Best Answer

To put it simply: yes, using the installer provided by the App Store is sufficient. Keep in mind that Apple develops and designs these installers specifically so that users, like you, can update to the newest system.

All you need to do is click the download button and follow the onscreen instructions to update.

There is always a risk factor of something going wrong; an obscure file missing, a .plist value out of whack, etc. The unfortunate truth is that there is always going to be potential human error.

Something to remember is that the error in question could come from something the new system added, rather than something the installer forgot to remove.

Using the installer is just a quick and easy way to update with a small chance of error. It adds new files and replaces outdated ones. If you wipe the system clean and freshly install a new one, there is still a small chance of error.

Mounting the volume

Disk Utility verification and possible repair of the partition map

If you have not already done so, use Disk Utility 13 (426) in OS X 10.8 to select then verify:

not the greyed-out partition
instead, the physical disk that contains the partition.

If verification reveals a problem with the partition map, then consider allowing Disk Utility to attempt a repair.

Proceeding without Disk Utility

Credit to Caesium's answer for finding the asr suggestion.

Here with a disposable JHFS+ volume, an example of adjustments working as expected. Note the file system checks:

macbookpro08-centrim:~ gjp22$ diskutil unmount /dev/disk12s1
Volume sandpit on disk12s1 unmounted
macbookpro08-centrim:~ gjp22$ sudo asr adjust --target /dev/disk12s1 --settype "Apple_UFS"
Fsck /dev/disk12s1 ....10....20....30....40....50....60....70....80....90....100
Adjust completed successfully
macbookpro08-centrim:~ gjp22$ diskutil list disk12
/dev/disk12
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *256.9 MB   disk12
   1:                  Apple_UFS sandpit                 256.9 MB   disk12s1
macbookpro08-centrim:~ gjp22$ diskutil mount readOnly /dev/disk12s1
Volume on disk12s1 failed to mount
macbookpro08-centrim:~ gjp22$ sudo asr adjust --target /dev/disk12s1 --settype "Apple_HFS"
Fsck /dev/disk12s1 ....10....20....30....40....50....60....70....80....90....100
Adjust completed successfully
macbookpro08-centrim:~ gjp22$ diskutil mount readOnly /dev/disk12s1
Volume sandpit on /dev/disk12s1 mounted
macbookpro08-centrim:~ gjp22$

If the type of your own /dev/disk0s4 can not be safely adjusted or (re)set to Apple_HFS then:

the operating system may no longer work with the HFS Plus file system (or remnants thereof) that occupies, or occupied, the affected area of the physical disk; and
you might doubt the integrity of the partition (start and end blocks, and so on).

Relevant lines from /private/var/log/install.log should reveal what, if anything, happened to disk0s4 before, during or after installation of the OS to disk0s2. This logged information may become critical to regaining easy access to the data.

Getting the data without mounting the volume

Good luck with your use of Data Rescue 3 – I have the app, but have never attempted to recover from any area of a disk where the partition type has been affected in this way.

Observations

Device/media name

This is sometimes, not always, a match for the volume name. Here for example:

macbookpro08-centrim:~ gjp22$ diskutil info disk0s2 | grep Name:
   Device / Media Name:      swap
   Volume Name:              swap
macbookpro08-centrim:~ gjp22$ diskutil info disk0s4 | grep Name:
   Device / Media Name:      Untitled
   Volume Name:              spare

For Todd K., presence of the device/media name –

MacBook Data

– raises hope that start and end blocks etc. are good, that only the type of the partition is wrong.

No Recovery System 10.8 for OS X 10.8

Recovery HD implies Recovery OS 10.7.x.

In any case such as this, an installation that is incomplete (that is without the expected upgrade to the Apple_Boot slice) signals that a nonstandard method of installation – with only part of Apple's installer app – may have been used.

Side note

GUID Partition Table, as it's described in Disk Utility, is the norm for this type of modern installation of OS X – not Master Boot Record.

MacOS – Clean reinstall of Mountain Lion deleted the iLife applications. How to get them back

This depends on whether your copy of iLife was purchased through the App Store, installed from DVD, or was just the version that came with the MacBook originally. If you had purchased from the App Store, it should be just as easy as going to the app store and redownloading your apps. If not, then you'll either need to reinstall from DVD or purchase the new versions of iLife. Your MacBook should have come with an install DVD for both OS X, and for iLife.

Another solution is to use the Migration Assistant and Time Machine to restore your apps. That's by far the easiest way to get all of your old stuff on your new system. Of course, it'll pull in more than just iLife.

Finally, if you have a Time Machine backup, you can still restore from it. Option-Click on the Time Machine icon at the top right, and choose "Browse Other Backup Disks". That will let you get into the backup from your previous setup.

Good luck!