Booting
Operating
Systems
Boot
System
Selection
The
Boot
ROM
provides two modes
of
operation,
attended
and
unattended.
These two modes
allow a user
to
either
select from multiple
operating
systems on multiple
boot
devices
or
to
automatically
boot
an
operating
system
with
no user intervention.
Unattended
Operation
In
an
Unattended
situation,
the
first
operating
system found will
be
loaded
and
given control.
To find
an
OS,
the
Boot ROM will search a
boot
list of prioritized devices.
The
first OS system
found on one
of
these
devices will
be
booted.
If
none is found,
the
boot
list will
be
searched
again until a one
is
found.
This
allows discs
not
present
at
power-up
to
be
found after
their
initialization is complete.
Once a device has been successfully accessed, it will never
be
accessed again until re-power-up
or
a reset.
This
mininlizes wear on mass storage devices
and
limits
the
confusion of
operating
systems disappearing
and
re-appearing on
shared
resource
management
systems.
To force
the
boot
of a
particular
system
when
the
machine
is
unattended,
the
user has
the
following options:
• Make sure
that
the
OS
to
be
booted
is
the
first
to
be
found according
to
the
boot
list
search.
This
is
quite
easy
to
do sirnply by changing device addresses, select codes,
or
OS
names,
or
by moving OSs.
The
prioritized
boot
list is discussed in detail
latter
in
this
section .
•
On
an
SRM
with
multiple OSs, make
the
first OS
to
be
found one
that
looks
at
the
host's
SRM node address
and
uses
the
node address
to
decide
what
secondary OS
to
boot.
(The
Boot
ROM
can
then
be
called
to
boot
a
particular
OS.)
Attended
Operation
To force
the
boot
of
an
OS
not
chosen by
the
boot
list,
the
user
must
enter
Attended
Operation
Mode.
This
mode is
entered
by pressing
the
space bar, I RETURN
I,
or
any
letter
or
number
during
power-up
after
the
input
portion of
the
hurnan interface (i.e.,
the
keyboard
or
terminal)
has
been
initialized
but
before a default OS is booted. A good way
to
do
this
is
to
hold down
the
space
bar
until
the
OS selection menu
is
seen.
This
will cause a
boot
selection menu
to
be
displayed.
A user
can
be
sure
that
the
input
human
interface has been initialized when one
of
the
following
(depending on
the
hurnan interface provided)
is
displayed in
the
self-test list:
Keyboard
Console Keyboard
at
XX
HP
986XX
at
X
w here XX is
the
lowest select code of key
board
electronics
in an
I/O
slot.
w here
the
Xs are
the
type
and
select code
of
the
remote
human
interface.
Boot
Rom
Functions
93
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