Free space wierdness

[Herbert Wolverson]

I have a system running FreeBSD 4.9-RELEASE. It primarily functions as a firewall and 
router, and is generally pretty lightly loaded (load averages around 0.2). It
is a low end system (P200, 64mb RAM, 2 gig hard drive), and is generally
stable as a rock.

The system has drives setup as follows:
/	256M (UFS)
/usr	1.2gb (UFS+Softupdates)
(/var and /tmp are linked onto /usr/var and /usr/tmp respectively)

This morning I noticed that the "/" partition was at 108% utilization,
and "df -h" looked like this (approximately):

Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/ad0s1a   252M   256M  -8M    108%     /

Oddly, "du -h -d1 -x" showed only a total of 29Mb used on the partition!
The output looked like this:

su-2.05b# du -h -d1 -x
 68K    ./dev
2.0K    ./usr
2.7M    ./stand
1.3M    ./etc
512B    ./proc
4.0M    ./bin
542K    ./boot
2.0K    ./mnt
6.4M    ./modules
 30K    ./root
 12M    ./sbin
4.0K    ./tmp
4.0K    ./oldvar
 29M    .

When I rebooted the system (without deleting any files), "df -h" showed
the following:

Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/ad0s1a   252M    29M   203M    12%    /

This is good, since the correct amount of free space now shows, and the
server is back to running perfectly. Can anyone shed any light as to why
this discrepancy happened in the first place? I'd love to know what I can do to avoid ever having to worry
about this again!

Thanks,
Herbert Wolverson,
The Turner Stephenson Group, Inc.
http://www.tsghelp.com/