By Graham K. Rogers

I had delayed updating my OS X rescue disks for too long, mainly because it did not matter, up to a point. This was not an extension of the "It will never happen to me" syndrome, but if there had been any emergency on one of my Macs, I had a spare MacBook Pro ready to help with repairs.

Outline

One of the reasons I had delayed this process for the external disk was that - apart from Time Machine backups - it contained the only copy of several Aperture libraries. As I had recently backed those up on to two more external hard disks - there is nothing as safe as redundant systems - I now had some flexibility if the OS X update had gone wrong. It didn't.

With the new Mac, there was a work-round that I used when I decided to run maintenance with Disk Warrior: I started the 13" Mac in Target mode and ran the repair from the 15" MacBookPro, although I had to use a Firewire to Thunderbolt adapter. As that machine may be heading for a friend, it is time to update the rescue disks.

Flash Drive (1)

• Macintosh HD
• Recovery 10.9
• Rescue (the flash drive)
• Recovery 10.8

I selected the Recovery disk and pressed the Enter key. USB drives are always slower and it took a minute or two before the screen changed. First I had to pair the trackpad (or connect a mouse) and also select a network, which meant hunting round for the right password. When I did eventually access the option to install a version of OS X, I saw that I was being offered 10.8 so I aborted that.

I then started 10.8 on the iMac from the flash drive but when I tried to download Mavericks, was told that the disk was full. I tried another couple of ways to make the installation, but I was limited by space. Each time I was stopped before I started. I would have to wipe the disk and start again.

I knew that it was possible to install a version of Mavericks on an external drive like this, but it is not as easy as it used to be. I examined several sources that talked me through this, focussing on

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

Each suggested alternatives, such as Diskmaker X, but all included a method that used the Mavericks installer and Terminal. An important point was that this method would also create the Recovery partition. I read all three articles several times and had to make a number of changes to the way I would normally work, first by switching to the Admin account. This is essential as the command begins with sudo and that does not work in a user account.

The second point - as with installing on external media with Mountain Lion - was not to run the installer. I make this mistake every time when updating on a Mac. As the process deletes the installer when the installation is complete, it is gone unless the user aborts the process: before it starts.

External Disk

I restarted the 15" MacBook Pro a couple of times, connected the disk using the USB cable, then (as with the flash drive on the iMac - above) restarted with the Option key pressed. From the four disk icons shown as available, I chose the "Recovery" drive and this started the MacBook Pro in OS X from the external disk.

As earlier, I was asked to connect to a network, but this time I had the password ready. I was not asked to connect a mouse or trackpad as this is a built-in feature with the MacBook Pro. When the desktop appeared, I started the Mac App Store. Mavericks showed a free upgrade of course. I clicked on that and was prompted for the iTunes account details. Once entered, the download began.

In the other room, the download in the 13" MacBook Pro was just finishing. What I did not want was to install it. Instead of going ahead, I quit the installer and saw that the app, Install OS Mavericks, remained in the Applications folder. With a small leap of faith, I logged out of the User account and opened Admin.

Over on the 15" MacBook Pro, once the installer was downloaded, I let the software do its job and waited for the restarts. First the new OS version overwrites the old. This took 50 minutes. Then everything is put in the proper order. After crawling along for an age, the blue progress bar suddenly leapt to the end and reported, "Completing installation".

It restarted again and there was another progress bar (around 7 minutes or more). When it did restart I had Mavericks - OS X 10.9.2 - on the external disk controlling the 15" MacBook Pro. But more to the point, would it start the 13" MacBook Pro with Retina display? . . .

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.