ext3 zerofree option and RedHat back port?

Ron Yorston rmy at tigress.co.uk
Wed Sep 24 08:23:20 UTC 2008

Andreas Dilger <adilger at sun.com> wrote:
>> Ulf Zimmermann wrote:
>> Ok, so you really want to zero the unused blocks in-place, and e2image
>> writing out a new sparsified image isn't a ton of help.
>> The tool does that, I guess - but only on an unmounted or RO-mounted
>> filesystem, right?  (plus I'd triple-check that it's doing things
>> correctly, opening a block device and splatting zeros around, one hopes
>> that it is!)
>That is WAY to scary for me on a mounted filesystem.  It is racy if the
>blocks become allocated.

The 1.0.0 version of the zerofree utility only worked on unmounted
filesystems, but then someone suggested that it should be safe on
a read-only mount.  Is that not so?


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