Date: Thu, 21 May 1998 10:57:36 +0930 From: Greg Lehey <grog@lemis.com> To: "Brian O'Connor" <boc@ironbark.bendigo.latrobe.edu.au>, freebsd-questions@FreeBSD.ORG Subject: Re: seperate / /usr and /var partitions Message-ID: <19980521105736.M22701@freebie.lemis.com> In-Reply-To: <199805202311.JAA24553@ironbark.bendigo.latrobe.edu.au>; from Brian O'Connor on Thu, May 21, 1998 at 09:11:42AM %2B1000 References: <199805202311.JAA24553@ironbark.bendigo.latrobe.edu.au>
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On Thu, 21 May 1998 at 9:11:42 +1000, Brian O'Connor wrote:
> Hello,
> I admin a medium size network of SGI machines, as well as
> a couple of DEC and SUN servers and an increasing number of
> FreeBSD and Linux boxes. All my training, and most of my experience
> has been with either IRIX or Digital(or should that be Compaq) Unix.
>
> One of the many differences(advantages?) between IRIX and other Unixes?
> is that by default the IRIX install creates a single root partition,
> ie no seperate /var or /usr partitions. Three or four times now I have
> had problems with the DEC,SUN and FreeBSD servers in that the /var
> partition fills up, and/or the root partition is too small(esp with DEC
> OS upgrades, the new V4.x needs a bigger / partion).
>
> I feel ridiculous hunting for free disk on a 64MB / partion of a 36GB
> raid array on the DEC 2100.
>
> I have just setup a new freeBSD(2.2.6)server(1.5GB disk), and this time
> configured it with a single root partion. The install process warned me
> about this, asking me if I was sure that I new what I was doing.
>
> I think I'm sure.
>
> Are there technical reasons for the seperate partions beyond the classic
> need for a nfs mounted /usr(not applicable here).
We've discussed this a few times, and in the end we have agreed to
differ. The arguments are:
1. It's good to have a small root file system in case your system
crashes with such force that a file system is no longer mountable.
Since the small / normally does not change, it's unlikely to crash
hard, and it has (barely) enough tools to recover the other
file systems.
2. It's good to have the /usr file system read-only (same reasoning).
This means that /var and /usr can't be the same file system.
I subscribe to (1). I don't subscribe to (2). My recommendation (see
"The Complete FreeBSD", second edition
(http://www.cdrom.com/titles/os/bsdbook2.htm)) is to have a 40 MB root
file system and use the rest of the disk for /usr. Put /var on
/usr/var and make a symlink.
An alternative would be to put / and /usr on a single file system (how
big? Don't know, probably about 300 MB), make it read-only, and put
directories like /usr/share, /var and probably /usr/local on a second
file system. On the whole, I think this is less desirable: the system
very seldom crashes hard (I've been running *BSD on multiple machines
since March 1992, and it only ever crashed hard on me. As luck would
have it, it affected the root file system), and it's more difficult to
determine the size of a combined /usr and / than it is to determine
the size of /.
Greg
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