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Possible Duplicate:
ext4: How to account for the filesystem space?

After googleing a little I find that ext4 reserve 5% for root: Reserved space for root on a filesystem - why?, ext2/3/4 reserved blocks percentage purpose. And if I use tune2fs to set the number of reserved blocks to 0, it will take them back. But I use that code on a 100MB volume and get half of the reserving space, it was 10.5MB, and after setting to 0 the used space became 5.5MB. Why is the used space still not zero?

I used the following command to set the reserved space:

tune2fs -m 0 /dev/mapper/truecrypt1
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marked as duplicate by Gilles, jasonwryan, Mat, Caleb, Chris Down Nov 17 '12 at 23:36

This question was marked as an exact duplicate of an existing question.

What command did you use to view the reserved space? Remember ext4 needs some room to live in, too. You may want to try /sbin/tune2fs -l /dev/mapper/truecrypt1 and look at the Reserved block count line. – Michael Kjörling Nov 16 '12 at 9:24
up vote 0 down vote accepted

There is still space required for the filesystem's internal usage (superblocks, etc). This is merely the way ext4 works and defines "used space".

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