[sclug] Moving root filesystem from one drive to another

Dickon Hood sclug at splurge.fluff.org
Thu Aug 3 20:58:30 UTC 2006

On Thu, Aug 03, 2006 at 20:38:55 +0100, Tom Chance wrote:

Note: everything I say here may be wrong.  These are just my opinions.

: What's the advantage in having so many separate partitions? I can understand 
: it for /boot and /home but the others baffle me :o)

/home is fairly obvious.

/var is for writeable files, and will fill up.  Full filesystems are
generally a bad thing -- indeed, Solaris UFS can kernel panic in extreme
situations, and I'm told that's not uncommon amongst operating systems --
so anything written to needs to be thought about.

You also have spool files in there (mail, news) which can grow
considerably, and may be under heavy use, so a fast set of discs might be
nice.  Application dependent.

/usr should be mountable read-only.  Nobody actually does this of course,
as it's too much hassle when upgrading the OS or installing new packages,
but it's a nice idea.

/opt is contentious.  Some hate it (me, for one) and don't use it; others
say /usr is for the OS, and /opt for packaged non-core software.
Personally, I feel the OS and packaged software should be happily
non-conflicting in /usr, with anything outside the package management
system living in /usr/local -- this is the approach that most of the linux
distributions take, SunOS, *BSD, IRIX, etc. doing likewise.  Your Oracle
package will probably install here.  Again, should be read-onlyable.

/boot is a hack for crap PC hardware.  The less said about it the better.

/tmp should be mounted on swapfs.  /tmp is for small, very temporary
files.  swapfs / tmpfs are filesystems optimised for this usage, and
usually never writes anything to disc.  Much faster.  For anything bigger,
use /var/tmp; it's what it's there for.

/root shouldn't really exist.  root's home directory ideally should be /;
several standard Unix utilities rely on this (I've no idea why either),
although their GNU equivalents obviously don't.  Not a filesystem anyway,
just thought I'd comment.

/export is usually where users' home directories are mounted on the likes
of Solaris.  I'm not entirely convinced by the idea -- it presupposes an
intention to NFS export them -- and generally use /home as most sane
people do.

/net is for dynamic NFS mounting, via amd.  This is ... interesting.

There is one Sun guru by the name of Adrian Cockroft who recommends the
split-the-filesystems approach on servers, and the one-big-filesystem-to-
rule-them-all for desktops.  I'm inclined to agree, but rarely bother.  At
the BBC we had one big filesystem for all the usual, plus a /content where
all the content goes.  Simple, works.

Use whatever you feel happiest with.  But it can be a right pain in the
proverbial if you split everything and get the sizes wrong, and for the
type of workload people on this list are likely to be generating,
splitting isn't worth the bother.

Dickon Hood

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