Date: Thu, 11 Nov 2010 14:09:03 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Matthias Apitz <guru@unixarea.de> Cc: freebsd-questions@freebsd.org Subject: Re: how to overwrite the content of a file Message-ID: <20101111200903.GA57869@dan.emsphone.com> In-Reply-To: <20101111200252.GA1350@tiny.Sisis.de> References: <20101111200252.GA1350@tiny.Sisis.de>
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In the last episode (Nov 11), Matthias Apitz said: > What is the best method to overwrite the blocks of a given file with bytes > of 0x00, i.e. not to O_TRUNC away the blocks to the freelist of the file > system, but overwrite the old blocks? > > I've checked > > $ dd if=/dev/zero of=file count=4 > > but dd(1) opens the file with O_RDWR|O_CREAT|O_TRUNC which for sure will > give away the old blocks and adquire new blocks. Any idea? conv=notrunc (note that this will only help with ufs; zfs is always copy-on-write, so newly-written data never overwrites the old blocks) -- Dan Nelson dnelson@allantgroup.com
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