Time machine is a simple backup application, one of a Mac's best features. Data backed up using Time Machine can be a lifesaver when you lose vital data due to inevitable circumstances. However, like other backup applications, even the time machine could also be subjected to errors and issues that would cause severe threats to your backup copy. One commonly encountered Time machine error is "The backup volume is read-only." Due to this error, you will not be permitted to store or backup new data to Time Machine drive until the error is fixed.
Various solutions help you troubleshoot this sort of time machine error. Sometimes, the operating system assumes that the drive’s permissions are changed to read-only mode. In such cases, you can try resetting the permissions and fix the issue, but this method may sometimes fail and not yield the expected results.
Even turning off the time machine would help you in solving the error. To do this, you must open System Preferences, click on the Time Machine preference pane, and then move the slider to the OFF position. Suppose you use an external hard disk as a Time Machine backup volume, then try to eject the drive from your computer and reconnect the drive or restart the computer.
If the Time Machine drive isn’t mounted on the Desktop, you can unmount the drive to fix the issue using Disk Utility (located in /Application/Utilities). For this, select Time Machine drive from the Disk Utility sidebar and then click on the Unmount button situated in toolbar. After unmounting the drive, disconnect the cable, and later, you can plug in the drive; now, the drive should work fine.
These are the most commonly used and effective methods to fix the backup volume of a read-only error on a time machine. However, if the error is not fixed at the earliest, it could lead to Time Machine failure, causing massive data loss. Use Remo Recover (Mac) software if you have lost your data. The tool is designed to recover data after a Time Machine failure in just a few minutes. It supports data recovery from any Mac OS version, including the latest Yosemite.