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  1. #1

    dosfsck finds errors on vfat drive -- are these repairable or will I lose data?

    I ran dosfsck (also called fsck.vfat) on an almost-new external hard drive. It reports nearly a thousand errors, almost all of which are of the same type (as shown below -- I've trimmed down the repetitive nonsense so you don't have to scroll much).

    Can anyone explain what these errors mean, practically speaking? Have I already lost data because of this, or will I lose data if I let dosfsck autorepair, or is it safe to allow dosfsck to autorepair the disk?

    Should I archive off the data and reformat, or just let autorepair do its magic?

    $ dosfsck -n -v /dev/sdb1
    dosfsck 3.0.1 (23 Nov 200
    dosfsck 3.0.1, 23 Nov 2008, FAT32, LFN
    Checking we can access the last sector of the filesystem
    Boot sector contents:
    System ID "MSWIN4.1"
    Media byte 0xf8 (hard disk)
    512 bytes per logical sector
    32768 bytes per cluster
    32 reserved sectors
    First FAT starts at byte 16384 (sector 32)
    2 FATs, 32 bit entries
    61033472 bytes per FAT (= 119206 sectors)
    Root directory start at cluster 2 (arbitrary size)
    Data area starts at byte 122083328 (sector 238444)
    15258274 data clusters (499983122432 bytes)
    63 sectors/track, 255 heads
    63 hidden sectors
    976768002 sectors total
    FATs differ but appear to be intact. Using first FAT.
    Cluster 12397 out of range (16781312 > 15258275). Setting to EOF.
    Cluster 28781 out of range (16781312 > 15258275). Setting to EOF.
    Cluster 45165 out of range (16781312 > 15258275). Setting to EOF.
    Cluster 61549 out of range (16781312 > 15258275). Setting to EOF.

    ... almost 1000 more of these ...

    Cluster 15216749 out of range (16781312 > 15258275). Setting to EOF.
    Cluster 15233133 out of range (16781312 > 15258275). Setting to EOF.
    Cluster 15249517 out of range (16781312 > 15258275). Setting to EOF.
    Bad file name.
    Auto-renaming it.
    Renamed to 000\0000000.\000\000\000
    Checking for unused clusters.
    Reclaimed 3724 unused clusters (122028032 bytes).
    Checking free cluster summary.
    Free cluster summary wrong (14872083 vs. really 14875807)
    Leaving file system unchanged.
    /dev/sdb1: 13890 files, 382467/15258274 clusters

  2. #2
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    How big is this drive? Unless you need to access the drive from Windows systems as well as Linux, then reformat the drive (and change the partition type) to use a Linux file system. If you need to access it from Windows, then reformat it as NTFS. FAT file systems are only reasonable on small flash devices and thumb drives that are not intended for long-term storage and efficient data access.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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