how do bootable usb sticks work?

[liamfordorme]

Hi, sorry I'm a noob. i am wanting to run osx yosemite from a usb, while mavericks is still installed on my actual ssd. Or is a bootable usb so that yosemite may be installed from the usb?

This is what i was going to follow- https://www.youtube.com/watch?v=C8mdoFuWiJE
will i be able to actually run the os from the usb and still access my files installed on mavericks?

 

[AlanShutko]

A USB flash drive is usually used for a bootable installer, not to actually run the OS. The link you posted shows how to do that. It still needs a separate drive to install to. This is a useful technique if you want to wipe your main drive and do a clean install.

If you have a big enough one, 64GB or bigger would work, then you can run the OS by installing onto it.

That said, most thumb drives are very slow, because they're designed for people to swap files, not to run a system on. I tried running Mavericks on a typical cheap thumb drive, and it took forever to boot. Installing it to a normal external moving hard drive worked much, much better.

If you've got a higher-priced thumb drive that's marketed for high performance, you might get much better result. I have a Lexar JumpDrive Triton that is quite fast. I haven't tried an OS install on it, but it might be tolerable.

 

[tywebb13]

Hi, sorry I'm a noob. i am wanting to run osx yosemite from a usb, while mavericks is still installed on my actual ssd. Or is a bootable usb so that yosemite may be installed from the usb?

This is what i was going to follow- https://www.youtube.com/watch?v=C8mdoFuWiJE
will i be able to actually run the os from the usb and still access my files installed on mavericks?

The guy in the video forgot to copy BaseSystem.dmg and Basesystem.chunklist to the root level of the usb. If you use his method, should do this too otherwise you will get errors.

The video requires you to unhide hidden files which renders your computer into a very vulnerable state. You can do a lot of damage if you mess about with hidden files. So this is best avoided if possible.

Here are 2 other methods that don't require you to unhide hidden files:

Method 1 (not using createinstallmedia)

Use and 8GB+ USB stick and format it with GUID partition mapping and a partition named Untitled, then run the following 5 commands in terminal:

sudo hdiutil attach /Applications/Install\ OS\ X\ 10.10\ Developer\ Preview.app/Contents/SharedSupport/InstallESD.dmg

sudo asr restore -source /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg -target /Volumes/Untitled -erase -format HFS+

sudo rm /Volumes/OS\ X\ Base\ System/System/Installation/Packages

sudo cp -a /Volumes/OS\ X\ Install\ ESD/Packages /Volumes/OS\ X\ Base\ System/System/Installation/Packages

sudo cp -a /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg /Volumes/OS\ X\ Install\ ESD/BaseSystem.chunklist /Volumes/OS\ X\ Base\ System

Method 2 (using createinstallmedia)

Right click on Install OS X 10.10 Developer Preview and then Show Package Contents. Open the Contents folder and then open Info.plist with textedit and change the string value of CFBundleShortVersionString from 1.4.3 to 1.4.1. Save the file.

Now format an 8 GB USB drive which should be called Untitled and formatted as Mac OS Extended (Journaled). The installer should be called Install OS X 10.10 Developer Preview.app and should be in your Applications folder.

Run this in terminal and wait about 20 minutes:

sudo /Applications/Install\ OS\ X\ 10.10\ Developer\ Preview.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ 10.10\ Developer\ Preview.app --nointeraction

 

[Porsupah]

That said, most thumb drives are very slow, because they're designed for people to swap files, not to run a system on. I tried running Mavericks on a typical cheap thumb drive, and it took forever to boot. Installing it to a normal external moving hard drive worked much, much better.

Or, indeed, a good SD Card - I wound up putting Ubuntu onto a SanDisk 40MB/s card, so I could boot into it without futzing around with repartitioning the SSD, given that's only an occasional need. Entirely self-contained, and doesn't use precious SSD space.