Repairing Mojave

Discussion in 'macOS Mojave (10.14)' started by blackxacto, Jun 2, 2019.

  1. blackxacto macrumors 6502a

    blackxacto

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    #1
    Anyone have a remedy for when Mojave Disk Utility finding errors and being unable to correct them? Why are repairs disabled?
     

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  2. pippox0 macrumors member

    pippox0

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    #2
    Backup on external hdisk, reformat apfs partition, restore back your data.
    Check if everything is good...
     
  3. blackxacto thread starter macrumors 6502a

    blackxacto

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    #3
    Are you saying that is the only solution from Apple? Disk Utility no longer repairs?
     
  4. chrfr macrumors 604

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    #4
    Is the disk formatted as APFS or HFS Extended?
     
  5. pippox0 macrumors member

    pippox0

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    #5
    You can try from recovery partition to use disk utility. I presumed that you have just done this without any result..
     
  6. fisherking macrumors 604

    fisherking

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    #6
    what pippox0 said, above. or, take a deep breath, make sure you're backups are running... and just work.

    i had a friend who had an 'unrepairable' warning in disk utility a few years ago; she just kept using her mac, without issue...

    EDIT: or, of course, run the combo updater: https://support.apple.com/kb/DL2000?locale=en_US
     
  7. ApfelKuchen macrumors 68030

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    #7
    Repairs have always been "disabled" if you're booted normally. You have to be booted to Recovery to run repairs.
     
  8. Honza1 macrumors 6502

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    #8
    Of course, Disk Utility will try to repair the disk. However, it depends:
    1. If the disk is HFS+, you must be running off different disk. Boot to recovery or some other disk and run DU from there.
    2. If the disk is APFS, it can repair in place. Sometimes, if it is possible.

    NOTE: not every disk error even can be fixed by Disk Utility. Do not expect miracles.

    In any case, before you do anything, make sure you have backup.

    At the end, erase/restore from backup may be easiest and fastest solution anyway. Fixing disk errors is tricky and may not be possible.
     
  9. ApfelKuchen macrumors 68030

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    #9
    For what it's worth, Disk Utility Help for Mojave still says to boot to Recovery to repair a disk. While you can run First Aid when booted normally (just as in older OSes), that verifies/detects errors, it does not repair them.
     
  10. blackxacto, Jun 3, 2019
    Last edited: Jun 3, 2019

    blackxacto thread starter macrumors 6502a

    blackxacto

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    #10
    The disk to be repaired is an internal HD , i broke the fusion and run from the 128 SSD. The internal 2TB is formatted APFS.


    Does anyone know why repairing from Recovery Mode is different from repairing from an externally booted drive w Disk Utility?
     
  11. ApfelKuchen macrumors 68030

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    #11
    It’s no different. Disk repair (file system repair, really) requires that the disk under repair not be mounted. That means booting the OS (and Disk Utility) from another disk or partition. That can be another partition on the same HD (the hidden Recovery partition, with its stripped-down version of macOS), a downloaded Recovery disk image running in RAM (Internet Recovery), or an external drive with a bootable OS.

    The difference between using an external drive and internal Recovery has more to do with hardware failures. The Recovery partition won’t boot if the physical HD failed (or the HD cable failed). Internet Recovery is dependent on an Internet connection. External drives can get you around those issues.

    Someone who services or supports multiple Macs can save time and effort by keeping bootable thumb drives with various versions of the OS. Rather than making multiple attempts to boot to a (possibly bad) internal drive, they go straight to the external. The time and effort that goes into making the bootable drives pays off down the road.
     
  12. Honza1 macrumors 6502

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    #12
    In my experience APFS can be fixed (at least some stuff) while being booted from. DU freezes data (kind of creates snapshot) and runs of that, if it find errors, it tries to fix them in kind of "second snapshot". At the end switches to fixed snapshot. Interestingly, it does not fix errors in the snapshots created by Time Machine and simply lets them age out in the 24 hours or so it takes.

    I have done that. Also, was advertised as one of the advantages of APFS. And is kind of cool - when it works ;-)

    Now, I am sure there are errors it cannot fix this way. But keep in mind, that with SSDs (for which APFS is anyway) any hardware error fixes are not accessible to OS - OS reads from a small computer called SSD ;-)... Tricks of old times of magnetic disks are not valid anymore. What OS can fix are some record errors in tables etc. That's it. Anything more than that and data are gone...
     
  13. ApfelKuchen macrumors 68030

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    #13
    PS. Apple’s Recovery system is cool because in many cases you can do the job without needing an external disk. Prior to Recovery you either booted to OS X Utilities from a DVD installer disk (if you hadn’t misplaced it), or from external drive. Heck, I remember booting on a daily basis from a floppy disk (dual floppy-equipped MS DOS, Apple II).
     
  14. blackxacto thread starter macrumors 6502a

    blackxacto

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    #14
    Boot from Recovery
    Thank you for your advice.
     
  15. ApfelKuchen macrumors 68030

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    #15
    Cool that you've been able to do some repairs. "Some" doesn't seem good enough to me. Until Apple says unequivocally that it's not necessary to run Disk Utility from Recovery to repair a disk, it's likely more time-efficient to boot to Recovery. One "maybe it'll work" pass at First Aid while normally booted, followed by a second pass in Recovery if the first fails? Why not cut to the chase?

    My philosophy is that Disk Utility > First Aid is there to deal with damage to the file system. Period. Perhaps that damage is due to bad sectors (HDD or SSD), maybe not. While Disk Utility will identify and quarantine bad sectors once found, the ability to repair the damaged file system is the crux of a successful repair. If the damage can't be reconstructed, it's time to erase and reinstall. "Tricks of old times of magnetic disks are not valid anymore" - well, both HDDs and SSDs can have sectors fail; we just expect that'll happen more frequently on an HDD.

    While HDD is everyone's favorite whipping boy for file system damage, there are several other major causes of damage. Some are addressed by APFS, others aren't. A "favorite" of mine, especially in particular MacBook models, is data communications-related - failures in the HD interconnect cable (the dreaded MacBook Pro flex cable). Bad connections = bad data. That can happen to either an SSD or HDD, and even with APFS. GIGO, after all.
     

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14 June 2, 2019