[BioC] alternate /tmp for Bioconductor install

[Robert Citek]

I'm attempting to install Bioconductor under Debian following the  
instructions here:

   http://www.bioconductor.org/faq.html#getBioC

Apparently, I don't have enough room in /tmp to untar the tar files.   
What is the "R way" to specify an alternate /tmp folder to use while  
installing Bioconductor?  "export TMPDIR=" comes to mind.  Also, can  
a failed install be "restarted" so that it will continue from where  
it failed?

Regards,
- Robert