Hey all ...
QUESTION:
I'm curious as to how file locking between multiple DOSEmu/DRDOS
sessions on the same, single system and single, local filesystem?
SYNOPSIS:
I need to run an DOS accounting program that accesses the same
files, although in multiple sessions. I think it handles its own
file management/locking, to prevent multiple sessions from touching
files (although I'm not sure -- see below).
TECHNICAL INTRO/DETAILS:
- New User
Just got DOSEmu + DR-DOS 7.03 running. I originally used the
Caldera OpenLinux RPMs, but I ended up builting an up-to-date DOSEmu
and putting together a "lightweight" directory from the DR-DOS 7.03
disks. I love how DOSEmu can just boot a Linux directory.
It is actually located in /var/lib/DOSEmu, which is its own 2GB Ext2
(actually Ext3) filesystem. I'm not too concerned about security
(small office setup) and I'm running SUID (I need DPMI) with
"everything open," although the filesystem itself is mounted
"nosuid". I'm sure this is not ideal, but it will do for now.
I'm going to duplicate this setup at a client over 5 PCs.
[ SIDE NOTE: I probably need to talk to Caldera about "licensing"
since I think the DOSEmu image was only for qty. 1, and I see they
have a 5-pack DR-DOS (which is exactly what I need) license for
~$150. I just want to "get it running" first before I pay some
dough. ]
- Client's Software
This setup is for a client that is currently using some older
DOS-based, but DPMI-using, accounting software (Roundtable
Advantage). Their current "setup" is actually interesting. The
have a "server" PC running Concurrent's "Multiuser DOS 7" (which is
based on DR-DOS, some sort of DPMS/TaskMgr-based setup?) to run
_multiple_ "DOS consoles" and serve each one out to a serial port on
a multiport serial card.
>From what I can tell, all this Multiuser DOS allows them to do is
running "multiple" instances of DOS consoles and one instances of
the DPMI program under each. The serial connections run to Wyse
terminals.
Anyhoo, they just had their 3rd Wyse terminal go, and they'd rather
put in $500 Athlon PCs (and have a real network) rather than pay
>$1K for another one.
- File Locking Discussion
At first I figured there was some "fancy locking" going on c/o this
"Multiuser DOS," but I believe you don't even need this setup.
E.g., Roundtable's support site talks about some people running the
DOS DPMI program directly on multiple Windows clients
(non-terminal-based) with the files plopped down in an SMB share
(they all access). Outside of some Oplock issues (which are easily
tamed with Samba, unlike a native Windows server ;-), I've tested it
and it seems to work with multiple SMB sessions (to a Linux server
with Oplocks _off_ on the share).
So I think the program itself is "smart enough" to know what files
are and aren't in use. Not ideal, but its how it does it -- I'm
sure the SMB protocol and Microsoft insistence on enabling "Oplocks"
by default (for performance) reduces that. Still, I'd rather run
more "local" like the original Multiuser DOS setup, instead of
adding a network protocol to the mix.
Please read on ...
- Client Doesn't Mind Linux
I was going to push Windows 2K on the desktops, because I hate
9x/ME (and NT 4.)is no longer kept "up-to-date"), but the client
actually didn't mind the Linux idea because:
A) They are using terminals right now anyway!
(except 1 PC)
B) They don't want users loading stuff on the PCs
anyway
C) I showed him my centralized NIS/NFS server +
Webmin setup with Gnome/Nautlius/etc... on the
deskops and he liked it
(I can setup/clone Linux desktops in no-time)
D) Saves ~$250/PC, which is a 33% savings/PC
($500 Linux v. $750 Win2K)
E) Shouldn't require any maintenance
(I'm only available weekends)
- What I Had In Mind
I'm hoping just local access works as good, or even better, than SMB
w/o oplocks. The most simplistic way I think I could approach this
is by running multiple XDOS sessions on the single server, and
pumping their display to the other Linux PCs. That way, the file
access _is_local_, on the PC I designate as the "accounting DOS
system".
Again, I'm curious how good the "file locking" is between multiple
DOSEmu/DR-DOS sessions.
- Another thought
Is there _any_ advantage (or disadvantage ;-) to use MSDOS as the
"host" filesystem (i.e. /var/lib/DOSEmu) rather than Ext2/3 other
than security? Is it more/less compatible at all -- especially
regarding locking? I'm assuming Ext2/3 is better, because of the
locking, or does the Linux kernel + DOSEmu have some "tricks up its
sleeve" that would be better?
- Final Thanx ...
Thanx in advance ... I'm planning on producing a "HOWTO" for this
program if this setup works -- largely because _many_ people are
having issues moving to a Windows client/SMB share implementation
(largely because of the Oplock issues -- which requires unsupported
registry hacks), and I think running "native/local", like with the
MultiuserDOS/terminal but now only with DOSEmu/XDOS would be more
ideal than over Samba SMB mounts.
-- Bryan
--
Bryan J. Smith, Engineer mailto:[EMAIL PROTECTED]
AbsoluteValue Systems, Inc. http://www.linux-wlan.org
SmithConcepts, Inc. http://www.SmithConcepts.com
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