Juniper Systems Allegro DOS Manual - Manual (Page 199)

MS-DOS Page 5-39
The Allegro will start with a basic configuration instead of your usual
configuration. For example, device drivers for PC cards will not be
loaded and environment variables will be set to their default values.
Bypassing Individual Commands
If you suspect your problems are related to a specific command, you can
view each command individually and bypass only the command you
think may be causing the problems. To review individual commands,
follow these steps:
1) Reboot the Allegro by pressing the <ON/OFF> key for 8 to 10 seconds
(just until the screen clears). After the system starts, DOS displays the
following message:
Starting MS-DOS...
2) While the text is on your screen, quickly press and release the <F8>
key. One by one DOS displays each command in your CONFIG.SYS
file followed by a prompt. To accept a command, press <Y> for yes.
To bypass a command, press <N> for No.
3) When DOS finishes processing the CONFIG.SYS file, the following
prompt appears:
Process AUTOEXEC.BAT [Y, N]?
Press <Y> for yes, if you also want to view the commands in your
AUTOEXEC.BAT file.