Root File System Invisible File(s)

[Kerr]

I run a Pyramid MIServer 4/2 and have had a problem recently with the root 
file system filling up (hold on don't answer just yet) with no visible file 
that has has the amount of space that is missing.

At times there will be 5 megabytes free and it will vanish with no apparent
cause. The free space reappears with the same mystery.

I have looked at every file (visible to find/ls/du) in the root file system 
that has changed during the period of the when the space disappears and none of 
the files can account for the loss/gain of space.  

Yesterday the local FE was here and watched as the only files changing
were the /etc/.*tmp files (they were getting bigger) and poof there was
1 megabyte more of FREE space than minutes earlier.

Has anyone else experienced this? Does any net.person have an explanation?
Are there programs that create files with no directory entrys that can
change size at will? If there are such invisible files how does one find out 
what program is creating them?

Thanks for your time...

grant
(kerr at oodis01.af.mil)

Oh yes, /tmp/ is a separate file system, we are running OSx 5.0d.