vfat filesystem goes read-only

This entry was posted by on Monday, 26 July, 2010 at

I experienced some problems writing to my ubuntu backup server. The machine runs rsync every night to grab backup2l backups from production machines. The problem seems to be a vfat system (why I still use such a crappy format you wonder… it is simple enough to also work under MS windows). Anyway… found some good posts on this:


Now, the problem is exactly as explained in this post, yet the keypad stuff has nothing to do with it. Checking /var/log/messages yields nothing. Dmesg, however, goes berzerk:

[88396.976584] FAT: Filesystem error (dev sda5)
[88396.976585] fat_get_cluster: invalid cluster chain (i_pos 535540750)

Ok so I guess we’re having a faulty vfat system on our hands.

Luckily, somebody had the same problem with a vfat on a memory card:


So the problem can fixed:

sudo fsck.vfat /dev/sda5 -w -r

What this does: fix the FATs (which were for some reason munched up). -w means its immediately written to disk and not to memory to be written all the way at the end (although the command did not take long). -r means it asks the user what to do. This fixed the problem with an “Unable to create unique name” message from dosfsck when using -a (automatically repair).

One Response to “vfat filesystem goes read-only”

  1. Roberto

    Hey, I know it’s been 3 years since you posted this, but I need to say this: your post has saved my life (and my iPod)! Thank you!

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