A while back, after successfully saving my Time Capsule’s hard drive from gaping jaws of hell, I started getting an error when Time Machine tried to backup my iMac. Apparently, it found the Time Capsule’s backup volume to be “read only.” Of course, the drive wasn’t read only, as Time Machine on my MacBook continued to be able to backup just fine. Something was awry… again.

	The dreaded “read only” error message.

Looking around online, I wasn’t the only one with this problem. Gobs and gobs of people were in the same boat, and I wasn’t able to find a consistent or confident solution anywhere.¹²³

Left to my own devices, however, I came up with a fix by implementing some “rules of thumb” and some old-fashioned trickery. As always, keep in mind my “solution” may not work for you, and I’m not responsible for any damage you do to yourself, your Mac, or your reputation by following my instructions below.

Change Names

First, I realized my computers weren’t named correctly – and neither was my Time Capsule. The default names given to Macs (and Time Capsules) follow the First Last's Hardware model. (For example, the default name it gave my MacBook was: Brandon Hansen's MacBook.) Unfortunately, the long name and special character (i.e., the apostrophe) have been known to cause lots of problems. Even if I wasn’t having backup issues, I thought it would be a good idea to remedy this. I gave everything new, short handles, without spaces or special characters. For the computers, this was very straightforward:

1. Open System Preferences.
2. Click on the Sharing icon.
3. Change the text in the field next to Computer Name:.

	Your Mac’s name can be changed on the Sharing preferences page.

For the Time Capsule, it was slightly more involved:

1. Open AirPort Utility.
2. Click Manual Setup at the bottom.
3. Click on the TimeCapsule tab.
4. Change the text in the field next to Time Capsule Name:.
5. Click Update at the bottom.

	Change your Time Capsule name using the Manual Setup dialogue in Airport Utility.

I half-hoped this might fix the problem all by itself. The backup files on the Time Capsule contained the old, messy computer names, so I thought maybe once the computer names were changed, Time Machine would update the backup file names—or maybe start over with a new backup file. It didn’t do either. Instead, the backups continued to go to the same files, and the iMac still found the TC to be read only.

First Level Trickery

This gave me an idea, though. What if I could trick the computer into using a backup file with the new name? I manually changed the backup file name to match the new name, but this caused Time Machine to lose the connection with the old file and start a totally new backup. It was encouraging not to get the read only error, but: I didn’t want to wait forever for a backup-from-scratch and, more importantly, I didn’t want to lose the backups still in the old file.

Time to move on to…

Second Level Trickery

I stopped Time Machine backup (that had started from scratch) then:

1. copied the name of the new backup,
2. erased the new backup,⁴ and
3. changed the name of the old backup to match the new one I erased.

	You can copy, delete, change the name of, or otherwise mess with backup files on the Time Capsule.

I re-started the backup and viola! No error. After the backup completed, I tested out Time Machine and found all of the old backups were intact. It’s now months later and Time Machine has been running seamlessly. Roll up!

Notes

¹ Example of someone else with the same problem: “Time Machine Read Only Error.” Apple Support Discussions, 6 January 2008. Accessed August 2009 from http://discussions.apple.com/thread.jspa?messageID=6277068&.

² Another one: “Time Capsule Read Only.” MacRumors: Forums, 13 March 2008. Accessed August 2009 from http://forums.macrumors.com/showthread.php?t=453349.

³ And another one: “TimeMachine ‘read only’.” MacOSX.com, 24 June 2008. Accessed August 2009 from http://macosx.com/forums/mac-os-x-system-mac-software/301474-timemachine-read-only.html.

⁴ Actually, I re-named it and then erased it later. In retrospect, though, there’s no reason to keep it around.