Apple's free HD SC Setup 7.3.5 disk formatting and partitioning utility
can create standard A/UX partitions that are appropriate for MkLinux.
You can  download a copy now from:

   ftp://ftp.info.apple.com//Apple.Support.Area/Apple.Software.Updates/US
      /Macintosh/Utilities/Apple_HD_SC_Setup_7.3.5.sea.hqx

But Apple, in its infinite wisdom, made the utility brain-dead
so that it only works with Apple-brand drives. Here's a simple
ResEdit hack that allows HD SC Setup to work with any SCSI drive.

   1. Open a copy of HD SC Setup with ResEdit.
   2. Open the "wfwr" resource icon.
   3. Open the "wfwr" resource with ID 67.
   3. Change the "00" string to "FF".
   4. Save the modified copy.

You should now be able to use HD SC Setup to create A/UX partitions
on your non-Apple drive.

-- submitted by sjohnson@datadungeon.com. Details on the patch
   were culled from a post by Philippe Laliberte to one of the MkLinux
   mailing lists.

(See also What tools can I use to partition my disks?.)