[NTLUG:Discuss] Software RAID using file "device"?

[Stuart Johnston]

I have a server with two partitions, / and /home (not the best setup, I 
know).  The /home partition is coming very close to running out of disk 
space and I am trying to figure out a way to use some of the extra space 
on / without requiring a trip down to the data center.  This would only 
need to be a temporary solution.

When I setup the system, I didn't worry too much about the partition 
setup because I was using LVM, which I thought would allow me to easily 
re-allocate the partitions as needed.  It turns out not to be quite so 
easy since you can't generally resize an ext3 partition while it is mounted.

I was thinking about how in Linux, devices are treated like files and 
you can often use them interchangeably.  So, if I created a file on / 
then I could use it as a device in mdadm or lvm to combine linearly with 
the /home partition (which can be unmounted and resized remotely). 
Unfortuntately, neither mdadm nor lvm seem to be willing to work with a 
non-block device.

Any suggestions on how to make this work?

thanks,
Stuart Johnston