Wednesday, March 20, 2013

Time Machine Volume got Locked Due to Corrupt Disk Permissions

Time Machine volume is locked, what should I do? I am not able to access my Time Machine volume on my Mac machine after upgrade. How to fix Time Machine backup when it is locked?

Mac has a built-in utility i.e. Time Machine that automatically takes backup of the data. The issues mentioned above arise when a user upgrades the Mac. Therefore, if you are also facing the above mentioned problem in Mac OS X after upgrade, you need to check and repair the permissions associated with the Time Machine drive. In this situation, the Time Machine icon is replaced automatically with a simple volume like icon with a small lock on it, which represents that the volume cannot be mounted to access the data. Users try attaching their Mac hard drive to another Mac machine; however, are not able to retrieve the data because another Mac machine also treats it in the same manner.

In this situation, user needs to format the entire hard drive and rebuild all the Mac volumes using Disk Utility; however, formatting a hard drive causes data loss at a large level. A user certainly does not wish for such a resolution that results in losing the data.

Why it is locked?

Time Machine associates backup to the Mac Machine based on MAC address, which is unique for every machine and is associated with its Ethernet card. This information i.e. Machine’s name and MAC address is saved in an invisible file that is saved in the root of the Time Machine, which makes the drive to be connected with multiple Mac machines. The latest OS X versions might have altered the way these permissions within this file are accessed or the file itself. Therefore, to avoid such an issue, the user should be given the rights to change and reset these permissions with the terminal. Moreover, various internal and external Mac machine errors, such as power failure, improper or sudden system shutdown etc. in the permissions may lead to their corruption.

Manually Changing and Resetting Permissions

Before manually changing the permissions on the file using Terminal application (built-in in Mac OS X), figure out what the file is called, and then change the permission using the following steps:

1. Launch, type cd and press space bar on the keyboard.
2. Drag and drop the Time Machine drive on the running window.
3. Watch the command, which should look like: cd /Volumes/Backup and hit Enter key to execute this command
4. Type: ls –la
5. Execute commands i.e.
sudo chown `id -un` FILENAME
sudo chmod 400 FILENAME

Replace FILENAME (in both commands) with the error appeared while accessing Time Machine drive and output of the commands executed in step 4.

Note: You need to enter the password (after each of the two command executes) in order to get Time Machine drive back to work.

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