[CentOS] Repartitioning issues - advice needed, and info.

[Bruce Whealton]

Hello all,
       I have a couple problems with two Centos installs.  One is my
Dedicated hosting plan.  I have been trying very hard to build some strong
skills in system administration because the task apparently is more complex
than I imagined... or it appeared that way to a web developer, who reported
he was not a system admin and so even though he could do quite a bit on the
server - more than I could at the time - he felt my task of needing to fix a
partitioning problem on my systems needed to be referred to a system
administrator ( a role I'm trying to take on).  
       On my dedicated server, I have had a couple partitions that are quite
often full and one of them tends to fill up very quickly now.  The other
partition, I believe the /var partition seems ok now that I have moved most
of my accounts elsewhere.  I believe the databases were there and so by
moving accounts elsewhere, much space was freed up.  Not it is the /etc
partition that is full every other day.  It is a 10GB partition and most of
the data is in the mail spool directories.  I don't have many accounts, so
I'm not sure how to fix the issue.  I get thousands of spam messages and
yet, I just realized, they don't seem to be going to the email addresses I
have on that particular dedicated server - or the domains hosted there.  All
manner of problems develop when this happens. 
          So, this is on a 500GB disk with a good bit of free space, such as
in the home partitions.  My domains are setup like this:
/home/username/public_html.  So, If I setup the domain mydomain.com, I'd use
a username of mydom.  Anyway, this partition has available space on it.  How
can I (maybe?) shrink one partition, moving files as necessary, and then
increase the storage size for the 10GB partitions, /etc and /var?  Can this
be done without breaking things?  
         Second issue...  My business/development server...  Centos 6.4.  I
cannot boot into it now because the /tmp partition is full.  Most of the
fixes I found online involve what you do once you boot into it.  Initially I
was getting an error about Power Management and googling this turned up
info. Saying that a disk partition is full.  Indeed, checking the boot log,
that was the case.  It could not create files in the /tmp
partition/directory - no more space.  So, I was trying to get to a place
where I could delete some tmp files as a first step.  Since I cannot boot
up, and didn't know what to do from grub to address the issue, I tried
booting to live CD.  The files are locked, of course, and/or protected, or I
don't have permission to delete anything. Is there any way to from adjust
the size of the different partitions, shrink some space in one partition and
expand it/reclaim it elsewhere, e.g. the /etc partition?  Again, I cannot
boot to the desktop.  I got as far as the grub boot loader and didn't find
anything that would let me adjust partitions.

Thanks in advance for any help,
Bruce