Message-ID: <47FADE53.1DFBEE53@dessent.net>
Date: Mon, 07 Apr 2008 19:54:11 -0700
From: Brian Dessent <brian AT dessent DOT net>
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To: cygwin AT cygwin DOT com
Subject: Re: A FAQ regarding defrag and permissions of nonadmin files?
References: <ftel7t$b1s$1 AT ger DOT gmane DOT org>
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Gmane User wrote:

> The defragger I used was JkDefrag.  And there was the explanation, right in the
> online documentation.  The files to be defragged need to be accessible by admin.
>  I never suspected that something as system-wide as defragging would be
> dependent on a specific account.  Setting all files to go+rwx allows all the
> files to defrag.
> 
> This arrangement clashes directly with the unix practice of having all nonadmin
> user file permissions default to u+rw,go-rwx.  A unix user (not necessarily an
> admin, as I've never been) who wanders into the weird and wonderful world of
> Windows would think he/she found salvation in cygwin (and would mostly be
> right).  He/she (let's just say "It") would innocently and obliviously bring its
> Unix ways with it, and never be able to defrag.  I am baffled by why this caveat
> isn't documented in any defrag or cygwin posting/page that I've come across.

This is just patently false.  While it may be true that a defrag program
that runs in userspace needs access to a file to defrag it, that does
not in any mean that some special "admin" user needs access to it.  And
besides, most defraggers install as a service anyway, so they run as the
system.

$ touch file

$ chmod 600 file

$ getfacl file
# file: file
# owner: brian
# group: None
user::rw-
group::---
mask:rwx
other:---

$ perl -e 'print "a"x10240' >>file

$ perl -e 'print "b"x10240' >>file

$ contig -a file

Contig v1.53 - Makes files contiguous
Copyright (C) 1998-2006 Mark Russinovich
Sysinternals - www.sysinternals.com


c:\tmp\file is in 2 fragments

Summary:
     Number of files processed   : 1
     Average fragmentation       : 2 frags/file

$ contig file

Contig v1.53 - Makes files contiguous
Copyright (C) 1998-2006 Mark Russinovich
Sysinternals - www.sysinternals.com


Processing c:\tmp\file...
Summary:
     Number of files processed   : 1
     Number of files defragmented: 1
     Average fragmentation before: 2 frags/file
     Average fragmentation after : 1 frags/file


The file has been defragmented and there was no need for any chmod
go+rwx.

For the record I took a look at JkDefrag's source at some point in the
past and it made me shudder how badly coded it was.  I suggest
UltraDefrag which is open source and free and it installs a native
driver to do the defragmentation so there is none of this worrying about
who owns a file or what ACLs it has.  Since it has a native interface it
can even run at bootup before files such as pagefile.sys are locked.

Brian

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