I use a NAS to store files I do not directly need on my notebook hard drive (due to limited space on my SSD). From time to time I need to boot Windows and I regularly use this opportunity to scan my complete system for viruses. The installed free version of Avira Antivir, like most other free scanners (as far as I know), prevents scans on network drives. It is feature that is reserved for the professional version of Antivir. Apart from the safety aspect, this has annoyed me for some time.

Playing around with different mount techniques to get the antivirus software to scan my network shares, I eventually stumbled over symbolic links. What I did not know: you can create symbolic links not only of files or directories, but also network shares.

Symbolic links from network shares can easily created in with the mklink /d command. (Found it on MS TechNet and in the Windows 7 forum).

C:\>mklink /d "c:\folder" "\\NAS-NAME\folder"

You need administrative rights (an administrator shell). You can then browse into the newly created (linked) directory and also scan it with your virus scanner.

I just ran into an issue while trying to compact my Virtualbox hard drive images. On virtual NTFS filesystems I usually run defrag twice, then rely on a tool called sdelete (download page) to zero the free space within the image. Afterwards I use vboxmanage to reduce the image size.

This time either zeroing the free space or the shrinking process seemed to fail. The supposedly compressed images needed even more space than before. It took me a while to figure out what happened – the parameters of sdelete have changed:

C:\>sdelete

SDelete - Secure Delete v1.6
Copyright (C) 1999-2010 Mark Russinovich
Sysinternals - www.sysinternals.com

usage: sdelete [-p passes] [-s] [-q] <file or directory> ...
       sdelete [-p passes] [-z|-c] [drive letter] ...
   -a         Remove Read-Only attribute
   -c         Clean free space
   -p passes  Specifies number of overwrite passes (default is 1)
   -q         Don't print errors (Quiet)
   -s or -r   Recurse subdirectories
   -z         Zero free space (good for virtual disk optimization)

It feels like 99% of the tips concerning zeroing the free space by calling sdelete -c (the old option for zeroing) seem to be outdated. Even worse: the “clean free space” feature shows the same output as “zero free space”.

So this should (currently) be a working procedure:

1. Run the Windows “defrag” tool twice.
2. (Download and) run “sdelete -z” to zero the free space.
3. Use vboxmanage “modifyvdi IMAGE.vdi –compact” to reduce the image size.