Solved - iTunes Library cannot be saved (Error -54)

I saw this exception: -

iTunes Library cannot be saved (Error -54)

whilst attempting to backup my iPhone 5S using iTunes 11.4 on the Mac ( OS X Mavericks 10.9.5 ).

Google, as almost always, led me to the answer: -

...

I've already solved the issue, through repairing disk permissions.  (Applications>Disk Utility>Repair Permissions)

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Source: iTunes Library cannot be saved (Error -54)

In order to achieve this, I rebooted the Mac into, effectively, single-user mode ( known as Recovery Mode ).

Source: OS X Recovery
Source: OS X: About OS X Recovery

This is achieved by rebooting and, as soon as one hears the bong of life, holding down [cmd] and [r].

Once rebooted, one can access a limited subset of tools, including Terminal, Restore from Time Machine and, most importantly, Disk Utility.

DU allowed me to mount my disk ( note that this requires one to enter the OS X log in password to unlock/decrypt the disk, assuming that one is using FileVault2 for full-disk encryption ).

Once done, I was able to: -

• Verify and Repair Disk
• Verify and Repair Permissions

To be safe, I did BOTH, several times.

Once I rebooted into normal multi-user mode, I re-opened iTunes ( the 5S was still connected ) and was able to do a full backup without exception.

For the record, I do backup the 5S locally rather than to the cloud .....

I then further backup ITunes to various external USB drives, with/out Time Machine.

Which is nice .....