RT-11 Help - test-drb@ccmp.vtda.org

12 Jan 1999

...
 I dont know RT-11 (yet.) and am looking forward to the
experience.  But
before that happens the seller wants to purge some sensitive employee
files on the system.  Can someone tell me how to tell him to 1) move
through the directory structure, and 2) how to delete specific files (
some that span partitions 0 - du4 according to him ), and...  
On RT-11, as with many OSes, deletion of a file simply updates the
directory in some way to indicate that the file is deleted.  In some OSes,
it might mean removal of the directory entry which pointed to the data on
disk (or the list of pointers to retrieve the info).  In some, it may be
to mark the directory entry as a deleted file.

In the case of RT-11, it marks the disk space taken up by the file to be
'free'.  But until another file is written over that data, it remains,
and can be retrieved.

What they can do, however, is to delete all those files which they don't
want anyone to have access to, and then to 'SQUEEZE' the disk volume.
The squeeze process is similar to what Windoze does when it defragments
a disk volume, only RT-11 files are not fragmented - they exist as
contiguous files.  But the files are all moved to the beginning of the
disk (low block numbers) with all the free space consolidated to the
end of the disk (higher block numbers).  This will result in at least
those deleted files which existed between others being overwritten
with files being moved.  The only problem might be a deleted file at
the end of the volume (or if the quantity of deleted files are sufficient
that the moved files don't adequately cover the deleted ones).  It
should be possible to write a very short program which will determine
the last block used on the (squeezed) volume, and to write null blocks
to all disk blocks from there to the end of the volume.

Finally, RT-11 files cannot span RT-11 disk partitions.  An RT-11
file can only exist in the partition in which it is defined.  It is
possible, however, for a user application to make use of the system
library routines which allow full access to an MSCP disk -- in which
case doing the squeeze won't help.

What you may want to suggest to him is to

	1) Delete all sensitive files from all disk partitions
	2) Squeeze all disk partitions.
	3) backup all disk partitions (on a file, not device, basis)
	4) FORMAT all disk partitions (RT-11 Format doesn't really
	   do a low-level format except for specific devices, and
	   MSCP disks are not one that it will do -- with the
	   exception of RX33 diskettes)
	5) Restore the backed-up files to all partitions.
	6) Release the hardware to you... :-)

...
 Where can I find a good source of RT-11 info?  
Not counting the documentation which can be purchased for it...

right here is a good place... :-)

					Megan Gentry
					Former RT-11 Developer

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