The values you see for available free disk space (from either Finder or the
"df" command), depend on whether you login as "root" or with a normal user
(non-root) accounts. This is because A/UX 2.0 adopts UFS (Berkeley Fast
File System) as the default root file system with minimum free-space
threshold. UFS provides a mechanism that lets you specify the percentage
of disk space RESERVED FROM USE by normal (non-root) users to reduce disk
overhead and increase disk performance.
The percentage of space reserved for the Root file system shipped with A/UX
2.0 is about 5 percent, and the default percentage of space reserved for
the non-root file system is 10 percent on the UFS file system. This is
done via the -m option of the "newfs" command.
The point is that the root superuser has the privilege to see and use all
free disk space, including the reserved space, but other users see only the
AVAILABLE disk space.
If you really need some or all of the reserved disk space for normal use
and don't care about disk performance, use the tunefs(1M) command with the
-m minfree option to change the percentage of the reserved space on an
unmounted UFS file system. For example, the command,
tunefs -m 0
sets a UFS file system without free-space threshold. However, the disk
performance (throughput) is significantly lower than performance at the
default 10 percent threshold.
For more information on Berkeley UFS, refer to newfs(1M) and tunefs(1M)
manual pages.