By Graham K. Rogers

I had delayed updating my rescue disks for too long, partly as a standard download onto the external media would not work with the new 13" MacBook Pro with Retina display. As OS X 10.9.3 is imminent, and the spare Mac might be heading for a new home, this maintenance update for external media was overdue. While an external hard disk was easy to update, the installation on a USB flash drive had some initial difficulties.

Comments on the External Drive

When the update was completed, the new installation on that Rescue disk was able to start the older 15" MacBook Pro with no problem, but I needed to make sure that it would also start the new 13" MacBook Pro with Retina display as that was released with a version of OS X created after the basic 10.9. A standard 10.9 disk would not start the 13" Mac.

While I was updating the external disk on the 15" MacBook Pro, I was also downloading a version of OS X onto the 13" MacBook Pro, although when that was complete, instead of letting the installation go ahead as normal, I quit the Install OS Mavericks application and switched to the Admin account on the Mac.

Finishing the Flash Drive (1)

• Dan Frakes on MacWorld
• Hongkiat.com
• Andrew Cunningham on ArsTechnica

I did not need it, but I also opened Notes. The Terminal command I would use was there, synchronised from the entry I had made earlier in the day on the iMac. I inserted the flash drive and from one of the Safari pages copied the command - it is one line - into Terminal:

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

I did change the "untitled" in the command line to match the name of the disk, so my command line entry read

sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/Rescue --applicationpath /Applications/Install\ OS\ X\ Mavericks.app --nointeraction

When I pressed Enter, I was asked for the Admin password. I crossed my fingers.

As predicted (Dan Frakes), the 0% . . . 10% . . . 20% appeared and I let it get on with "Copying installer files to disk.

When all was done, I had the flash drive with the OS X installer on it. There was more to be done to make this run OS X.

Once the flash drive had the necessary files, I removed it and went back for a moment to the external disk. I needed to be sure that the updated OS X on that disk would indeed start the 13" MacBook Pro.

I shut down the Mac, inserted the USB cable into the port and once more restarted with the Option key pressed down. This would recognise available disks and perhaps save some time if there was a problem with the disk. As before, four icons were shown and I selected the Rescue disk. I pressed the Enter key and the Mac started (albeit slowly), so I had one working rescue option.

Finishing the Flash Drive (2)

I started the older Mac as normal then inserted the drive. When it appeared on the desktop, I opened it first in the Finder and clicked on the Installer file. The Installation setup panel appeared and I clicked Continue.

After the licence agreement, an icon for the main disk appeared. I did not want that, so checked the "Show All Disks" button. The flash drive was shown (15.67 GB, 10.29 GB available). I selected this and the installation began. The first stage which is setting up all the files, took about 3 minutes, and the computer restarted automatically.

The computer then displayed an "Install OS X" panel with a progress bar. It started at 24 minutes. . . . but this took a long time. In the end it was just over an hour before the computer restarted. That in itself took several minutes and I did begin to wonder if all was well.

Eventually, the screen changed its shade of grey and the Welcome screen appeared: select country, keyboard, wifi (enter password), don't transfer information, don't sign in with Apple ID (confirm), Terms & Conditions (confirm), set up account, don't register Mac (confirm) . . . Setting up.

Finally the desktop appeared and I transferred a copy of Disk Warrior to the flash drive. I also found that the Install OS X Mavericks file remained intact. Unlike installing on a Mac, it was not deleted when the process was done. That will be useful.

I shut down the computer and removed the drive. This is meant to be an emergency solution - something I can throw in my back-pack and carry around with no real weight - so the slowness (while a drawback) is to acceptable for the medium.

The final check was to see if the OS X on the flash drive would start the 13" MacBook Pro. With the drive in the USB port, I started up with Option key pressed. The expected 4 partitions were shown: Mac disk, the USB drive; and their two recovery partitions. As with the external disk, I selected the USB flash disk and pressed Enter. It took a few minutes, but the disk worked.

I have two more rescue options.

See also:

Just after I put this online, Dan Frakes put out another article on MacWorld about installing OS X on external media, with specific reference to Macs such as my 13" MacBook Pro that was released after Mavericks. It is a complex process, however.

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand where he is also Assistant Dean. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs. He is now continuing that in the Bangkok Post supplement, Life.