1 2 3 4 Previous Next 45 Replies Latest reply: Jan 17, 2014 11:34 AM by TinMass
G4Dualie (Michael) Level 1 Level 1 (70 points)

Files can’t be copied onto the backup disk because it appears to be read-only.

 

You may need to repair or reformat the disk using Disk Utility. If the disk can’t be repaired, you must use a different disk for backups. Open Time Machine preferences to select a different backup disk.

 

Why is Time Machine insisting my drive is Read-only, when in fact it isn't?
This is becoming a routine occurrence. What's troubling is the problem is easy enough to resolve by simply unmounting/mounting the Time Machine drive and selecting Back Up Now from the menu and it purrs like a kitten.

 

After performing the step outlined above, my latest Time Machine backup is tucked neatly away and everything is fine once more.


24-inch iMac 2.8GHz (early 2007), Mac OS X (10.7.2)
  • 1. Re: Time Machine could not complete the backup.
    Linc Davis Level 10 Level 10 (118,465 points)

    What kind of drive is it?

  • 2. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    It is a terabyte Mercury Elite AL-Pro from OWC. It's about three-years old now and it performs flawlessly. This particular issue regarding Time Machine began surfacing in the last couple of months.

     

    The drive runs like clockwork for days without a hitch, and then suddenly Time Machine declares the drive to be Read-only.

  • 3. Re: Time Machine could not complete the backup.
    Linc Davis Level 10 Level 10 (118,465 points)

    Run Repair Disk on the backup volume in Disk Utility, if you haven't already done so. It will take a long time, maybe hours.

  • 4. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    It's easier to unmount and mount the drive.

     

    DU hasn't been able to resolve this issue for the last few months so, at the risk of offending you, and because Time Machine has since performed two backups, I'll take a pass on running DU again.

     

    I created this comment to add one more voice to the discussion regarding Time Machines inability to recognize whether a drive is read/writeable.

     

    Thanks Linc.

  • 5. Re: Time Machine could not complete the backup.
    Pondini Level 8 Level 8 (38,720 points)

    G4Dualie (Michael) wrote:

    . . .

    I created this comment to add one more voice to the discussion regarding Time Machines inability to recognize whether a drive is read/writeable.

    Time Machine may have set it to read-only because it found a problem. 

     

    Sounds like there's a problem with the drive, perhaps beginning to fail.    If Disk Utility fixes it, but later on it turns up suspect.

  • 6. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    That's interesting Pondini. In the realm of possibilities, how would we test the veracity of your observation? In what log would I read an account resembling the process you describe?

  • 7. Re: Time Machine could not complete the backup.
    Pondini Level 8 Level 8 (38,720 points)

    You may see it in the system.log.

     

    There are some similar threads in this forum.

     

    Or, you could just try what two experienced users have suggested.

  • 8. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    Or, you could just try what two experienced users have suggested.

     

    Oh oh. You had to go there, Pondini?

     

    TM isn't resetting my drive to read-only, you made that up. Then, you have the nerve to go and suggest my drive is about to fail. Why would you jinx me like that, Pondini?

     

    I read and evaluate ALL the advice you give to forum members. Why wouldn't I? You are the most vocal people here. I respect your badges and your experience. You spend countless hours of your own personal time helping thousands of nubes and Windows converts resolve their problems and that's great and all...

     

    But, I want help from the person a Level 7 goes to, Pondini. Nothing personal, nor am I challenging you or your knowledge but quite frankly your TM advice is fundamentally basic common Apple-sense. ... cause Band-aids stuck on me.

     

    Disk Utility, or any File system utility for that matter, is not going to resolve this issue. The drive appears to be ok, is not necessarily so.

     

    This TM problem is a gathering storm. Google this Read-only issue! It's everywhere and not just here in this Apple forum.

     

    The bottom line is, we have to manually resume Time Machine backups every time TM fails and it's becoming annoying. You've been dealing with this matter for months and your advice is always the same; run DU or DW, which are File system utilities, and when those fail to affect any permanent repair, the fix is never positive.

     

    This issue is beyond the scope of this forum and won't be resolved until an Apple engineer gets involved. It's about time Apple began collecting data from our Macs regarding this issue.

     

    Perhaps ZFS is the answer to my problem?

  • 9. Re: Time Machine could not complete the backup.
    Linc Davis Level 10 Level 10 (118,465 points)

    Perhaps ZFS is the answer to my problem?

     

    Why didn't I think of that? Port ZFS to the Mac, then reverse-engineer Time Machine to work with it. Problem solved. Be sure to let us know when you're ready to release your code.

     

    While we're waiting, others finding this discussion might want to peruse the Apple documentation that pertains to the issue:

     

    If Time Machine is unable to complete a backup, make note of any alert message that appears. You can also open System Preferences and in Time Machine preferences click the red "i" icon for more information.

     

    Messages you may see after clicking the red "i" include:

     

     

    "The backup volume is read only."

    Attempt to repair your Time Machine's backup:

    1. Choose System Preferences from the Apple menu.
    2. From the View menu, choose Time Machine.
    3. Move the slider bar to "Off" to disable Time Machine backups.
    4. Open Disk Utility located in/Applications/Utilities

     

    1. Mount your external hard drive.
    2. In Disk Utility, locate your external backup drive. Your backup drive should mount in the Disk Utility sidebar when attached to your Mac.
    3. Select your external backup drive.
    4. Click Repair.

    Time Machine: Troubleshooting backup issues

     

    The fact is that under some circumstances, diskarbitrationd(8) can update the 'rw' (read-write) mountflag of an HFS volume to 'ro' (read-only) if the filesystem fails an assertion. That's not Time Machine; it's the Disk Arbitration framework. Such failures occur because the device hosting the volume has thrown an error. If it happens once, the correct response is to repair the volume directory, assuming it needs repair and can be repaired. If it happens repeatedly, the correct response is to suspect a hardware fault and test with another drive.

  • 10. Re: Time Machine could not complete the backup.
    Pondini Level 8 Level 8 (38,720 points)

    G4Dualie (Michael) wrote:

    . . .

    TM isn't resetting my drive to read-only, you made that up.

    No.  I don't know (and didn't say) that's necessarily what's happened in this case, but that it does happen, and might well be what's causing the problem here.   Your system.log may clarify what's going on.

     

    But, I want help from the person a Level 7 goes to, Pondini. Nothing personal, nor am I challenging you or your knowledge but quite frankly your TM advice is fundamentally basic common Apple-sense.

    Then you have some choices:

     

    Call AppleCare.  See the blue box in  Reporting a Problem to Apple.

     

    Use Apple's BugReporter.  See the green box in Reporting a Problem to Apple.

     

    Get a Developer's membership ($99/year), so you can download and test beta software, and file bug reports.  That would let you test "point" upgrades to Lion, and/or Mountain Lion.

  • 11. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    Perhaps ZFS is the answer to my problem?

     

    Why didn't I think of that? Port ZFS to the Mac, then reverse-engineer Time Machine to work with it. Problem solved. Be sure to let us know when you're ready to release your code.

     

    Okay, smartypants. Obviously you aren't aware of just how close we are to achieving that very thing you describe. You should get out of this cave more often.

     

    Don Brady's got our backs, k? Z-410 premium will be available this summer and for some of us, it's the beginning of the end of Finder's Folly.

     

    In the meantime, thank you for your interest. Personally, I'd like to see them just get rid of this embarrassing display of unprofessionalism.

  • 12. Re: Time Machine could not complete the backup.
    G4Dualie (Michael) Level 1 Level 1 (70 points)

    Time Machine may have set it to read-only because it found a problem.

     

    "No.  I don't know (and didn't say) that's necessarily what's happened in this case, but that it does happen, and might well be what's causing the problem here.   Your system.logmay clarify what's going on."

     

    You said it MAY have happened, followed by your proclamation that perhaps the drive is about to fail and you based that on what I wrote! You didn't ask for logs, or press for further information, like you have done with evey other thread in this forum.

     

    I'm done here.

  • 13. Re: Time Machine could not complete the backup.
    Pondini Level 8 Level 8 (38,720 points)

    G4Dualie (Michael) wrote:

    . . .

    You said it MAY have happened, followed by your proclamation that perhaps the drive is about to fail and you based that on what I wrote! You didn't ask for logs, or press for further information, like you have done with evey other thread in this forum.

    Correct.  I recommended starting with Repair Disk, as Linc did, because that usually fixes it, and you'd answered that recommendation with the rather snippy "It's easier to unmount and mount the drive."  If you'd made it clear you'd already done that, with a clean result, I would have gone further.

     

    I'm done here.

    As you wish.  Be sure to post back when you solve it.

  • 14. Re: Time Machine could not complete the backup.
    Steve Johgart Level 1 Level 1 (5 points)

    Yes, I know this is a very old thread, but I wanted to reply with my experience with the advice in the preceding question. I used Repair Disk, which didn't solve the problem. I then tried unmounting and remounting the drive, which did solve the problem. For a week or two - then the drive is again declared read-only until I unmount and remount it. While still in what TM claims is "read-only" mode, "Get Info" shows the disk read and write for me and for admin, but read-only for everyone; it will not allow me to unlock and change the permissions. This is under Mountain Lion - I don't recall it happening pre-Mountain Lion.

     

    Mountain Lion seems in general to have done something weird to the disk directories, since after upgrading to ML, SuperDuper! was so completely fouled up about which disks were mounted and which weren't, and which disks it should be using, that I had to fully delete (using MacCleanse) and reinstall SD - now it works just fine. Hopefully that will continue, and not periodically get fouled again up like TM seems to do. Of course, I do realize that the SD problem may be totally unrelated to the TM problem (possibly SD plist or something got corrupted in the Mountain Lion update), but the symptoms have enough in common to be somewhat suspicious.

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