Scrub free disk blocks

JD jd1008 at
Sun Aug 29 01:01:59 UTC 2010

  On 08/28/2010 05:42 PM, Patrick O'Callaghan wrote:
> On Sat, 2010-08-28 at 15:12 -0700, JD wrote:
>> On 08/28/2010 01:53 PM, Patrick O'Callaghan wrote:
>>> On Sat, 2010-08-28 at 10:46 -0700, JD wrote:
>>>> You need to study filesystem architecture to gain better
>>>> understanding.
>>> If you can't explain what you mean, just say so.
>>> poc
>> I can explain it alright - and I tried to tell you that a program
>> can access all blocks of a file, direct and indirect, given that
>> tha program has the access permissions for that file, but you ignored
>> it. Direct and Indirect blocks are only meaningful to the inode layer.
>> The file's offset will be computed and a block number arrived at. If
>> that block number is outside the range of the direct blocks, then the
>> indirect blocks are accessed. Enough said.
>> Explaining FS architecture is beyond the scope of this list, and
>> certainly beyond this thread.
> I've been using Unix since 1975 and am very well aware of how the
> direct/indirect addressing scheme works. And I still fail to see what
> this has to do with the scrub command. Are you saying that scrub
> overwrites these blocks when deleting a file? If so, what is your basis
> for saying so, given that the manpage explicitly states that "only the
> data in the file (and optionally its name in the directory entry) is
> destroyed"?
> OTOH if you're saying these blocks are irrelevant, you're contradicting
> your original requirement of scrubbing any free space.
> poc
Let me quote to you what YOU wrote:
On 08/28/2010 06:22 AM, Patrick O'Callaghan wrote:
> From scrub(1):
> -X, --freespace
> Create specified directory and fill it with files until write returns 
> ENOSPC (file system full),
> then scrub the files as usual. The size of each file can be set with 
> -s, otherwise it will be the
> maximum file size creatable given the user’s file size limit or 1g if 
> umlimited.
> However note that neither of these methods guarantees to scrub indirect
> blocks in the filesystem that were used to create the space-filling
> files. Maybe they do, maybe they don't, it's not clear.
> poc

It was you who made the off-the-wall and totally wrong statement that
indirect blocks of files created by the scrub process ARE NOT SCRUBBED!

You have exposed your ignorance of the filesystem architecture, and
mentioned something you vaguely remember the name of, and totally
embarrassed yourself before a very large audience.

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