On Sun, 31 Jan 1999, Jaromir Dolecek wrote:

> 
> I run out of disk space the  other day and df output looked a bit wierd:
> 
> dolecek~ > df
> Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
> /dev/wd0a      990582   961902   -20850   102%    /
> /dev/wd0e      708411   556513   115303    82%    /usr/emul/linux
> kernfs              1        1        0   100%    /kern
> procfs              4        4        0   100%    /proc
> 
> This shouldn't happen, should it ?

It's OK. Your evidently have 5% reserved on /; 961902-20850 = 990582x5%.
That minfree threshold (binding for ordinary users) is adjustable
using "tunefs". The root user is allowed to exceed the threshold, and
when that happens, you'll see a negative space avail, as you did.