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I want to upgrade from ML to Mavericks but I want to erase and format my HD to a single partition along the way. Is this possible?

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Yes you can use disk utility to reformat the Macintosh HD partition during the installation of Mavericks, however if you want to create a new partition using disk utility the you will have to create a Mavericks install USB so you can boot from there.

You can't create a Partition when booted from the same drive hence the need to boot from a USB installer.

Creating a USB installer is as follows, Format the USB thumb drive as a Mac OS Extended (Journaled) and name the USB thumb drive Untitled

Download Mavericks from the Mac App Store,

Copy and paste this command into terminal,

sudo /Applications/Install\ OS\ X\ --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ —nointeraction

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You're wrong. You can load up Internet Recovery and make any changes to the file system from that. It replaces the need for a USB installer. – user10355 Dec 16 '13 at 2:20
Wrong about what? What part of my answer is wrong? – Maximus Mar 7 '14 at 15:01
"You can't create a Partition when booted from the same drive hence the need to boot from a USB installer." You don't need a USB installer with Internet Recovery. – user10355 Mar 8 '14 at 3:14

If time (and bandwidth) is not an issue, you could upgrade your current drive to 10.9 first, which would also create the 10.9 recovery partition. Then, after booting into the 10.9 recovery partition, you could partition the drive via disk utility and then cleanly (re)install 10.9.

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I'm downloading now. Then I was thinking to just install it and erase whatever that's old. Is that what you mean? – Faq Dec 16 '13 at 0:12
No ... I meant to follow these instructions AFTER you've installed 10.9 for the first time: This will redownload the OS again, and go through the installation process a second time. From another Apple support page ( "If you use the Recovery System stored on your startup disk to reinstall OS X, it installs the most recent version of OS X previously installed on this computer." That's why you would need to first go through the regular 10.9 installation first. – Kent Dec 16 '13 at 0:54
OK. I'll think about it, thanks! – Faq Dec 16 '13 at 1:07
Using Internet Recovery is a better option. It will save you a lot of time and you won't need to install OS X twice. – user10355 Dec 16 '13 at 2:21
@cksum, As stated in the second link above, "If you use Internet Recovery to reinstall OS X, it installs the version of OS X that originally came with your computer"; not an upgraded version. – Kent Dec 16 '13 at 2:30

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