Subject: Re: Why root and usr in separate partitions?
To: None <>
From: Nate Johnston <>
List: netbsd-users
Date: 06/29/2001 09:19:46
Scott Horton spake thus: (Thu, Jun 28, 2001 at 10:43:10PM -0500)

> So - my question - in a single-disk system, why this longstanding tradition
> of breaking the filesystem up into multiple partitions?  (There!  I've
> unveiled my ignorance of *nix filesystems in general!)

First, there is no reason requiring this kind of a split.  I have seen
plenty of systems, particularly desktops, that have one gigantic /, and
the only other filesystem is swap.  While this is generally considered
Bad Form it is ok for a desktop.

Second, Unix has its roots in multi-disk server systems.  Your laptop
running NetBSD thinks more like a Sun Starfile E10000 than the same
laptop running Windows.  So, when I as a system administrator administer
large produciton unix systems I configure my desktop unices to be
similar.  Given the roots NetBSD has in old unix, and people like me who
have a utilitarian reason to make their laptops look vaguely like their
servers, more people accept multi-filesystem setups as the norm.

Third, it increases functionality through modularity.  I have to keep my
work data separate from other data as a corporate requirement, therefore
when I go into work I use a different /home partition on my laptop than
when I am at home (using the automounter).  Since filesystems are a
relatively static part of the system this doesn't usually come up much
but it is there.

Lastly, having multiple filesystems localizes errors.  If there is a
physical disk error, chances are that it is unlikely to be in the small
center track that contains my root and other boot-critical filesystems.
It is likely to be on an exterior track, where my /home, /export, or
/usr live.  The same process works for localizing application level
errors; here is an excerpt I got from a general google search "why does
unix use separate filesystems".  It is representative of the philosophy
and the mentality.


"You want to control how much data gets put on a drive. For example, in
some environments, I'll make /var/spool/lp/temp a small filesystem of
its own. This causes it to fill up if there are too many unfulfilled
print jobs, which calls attention to the problem before it really gets
out of hand and fills up something more important. The idea here is that
it's better not to print than not to work at all."


Nate Johnston                 
GPG footprint: DEAF B505 0D84 1AEF A43F  91C5 71B3 D053 D0E1 3C05
Unix System Administrator