Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!zephyr.ens.tek.com!tektronix!psueea!parsely!bucket!leonard
From: leonard@bucket.UUCP (Leonard Erickson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Command.com ISN'T invalid
Message-ID: <1843@bucket.UUCP>
Date: 24 Dec 89 07:05:56 GMT
References: <89121614031714@masnet.uucp> <320@infovax.UUCP> <25189@cup.portal.com>
Organization: Rick's Home-Grown UNIX; Portland, OR.
Lines: 34

Devin_E_Ben-Hur@cup.portal.com writes:

<The problem with "INVALID COMMAND.COM -- SYSTEM HALTED" does have to do
<with attempting to reload the transient portion of COMMAND.COM from disk.

<The problem is that the resident portion of COMMAND.COM *ignores* the COMSPEC
<environment variable.  If your shell is loaded from other than the root
<directory of the boot drive, the transient reload will fail unless you
<specify the correct re-load path as a parameter to COMMAND.COM in the initial
<SHELL= line of CONFIG.SYS.  So, if your COMMAND.COM is located in a
<directory named DOS on drive C, your CONFIG.SYS should have a line like:
< 
<SHELL=C:\DOS\COMMAND.COM C:\DOS /P <other switches>
<                         ^^^^^^ -- this tells it where to reload from.
<Note that, when the reload path is specified in the shell= line, there
<is no need to set comspec in your autoexec.bat, command.com will automatically
<make "COMSPEC=<load-path>\COMMAND.COM" the first line of your environment.

I must disagree with you. Some versions of DOS may act this way, but not all.
I ran a two disk system for *months* with comspec pointing to a copy of
COMMAND.COM in a ramdisk. And none of the reloads failed. There was no SHELL
line in my CONFIG.SYS, just a SET COMSPEC=C:\COMMAND.COM in my
AUTOEXEC.BAT. I know that reloads were occuring, because I'd had to set up
the ramdisk so I didn't get prompted for "inesrt disk with COMMAND.COM"
all the time.

Do note that DOS will cheerfully use a copy of command.com in the *current*
directory for reloading. So it pays to make sure that you only have *one*]
copy on your HD!
-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I'm all in favor of keeping dangerous weapons out of the hands of fools.
Let's start with typewriters." -- Solomon Short