SUMMARY: swap questions

From: Darryl Pace <>
Date: Wed Nov 07 2001 - 13:01:04 EST
First, thanks to the following for their replies:
Mark Neill, Justin Stringfellow, Kevin Graham, Darren Dunham,
Randy Romero, Casper Dik, Ray McCaffity, Dan Lowe, Thomas Lester,
Ric Anderson, Muhammad Mughal, Steve Camp, Gabel Martin, and Greg.

My original questions along with the answers I received are below.

-----Original Message-----
[]On Behalf Of Darryl Pace
Sent: Tuesday, November 06, 2001 2:09 PM
Subject: swap questions

	Three questions. First, how can you determine whether or
not a box is running the 32-bit or 64-bit OS?

Answer: The following command: "isainfo -kv"

	Second question, is it possible for a system running
the 32-bit OS to boot off the 64-bit OS, and if so, how?

Answer: "Yes.  If the system was installed with "64-bit support" then both
32-bit kernel and the 64-bit kernel were installed side by side.  The
32-bit kernel currently is always installed, the 64-bit kernel is the
option.  If you didn't install with "64-bit support" then you can add
the various 64-bit packages from the installation media rather easily.
They don't replace anything, they just add to what's already there.

The boot(1m) manpage describes how to boot either the 32-bit kernel or
the 64-bit kernel.  Summary:

	boot disk kernel/unix

	boot disk kernel/sparcv9/unix

Or set the boot-file nvram variable to either "kernel/unix" or
"kernel/sparcv9/unix" (note that the lack of leading "/" is intentional)
to make either one the default.  Use diag-file instead of boot-file if
diag-switch? is set to true."

	Last, the following messages appeared in the messages file:

Nov  6 04:49:36 host1 unix: WARNING: /tmp: File system full, swap space
limit exceeded
Nov  6 08:48:05 host1 unix: WARNING: Sorry, no swap space to grow stack for
pid 2227 (dtscreen)

here's what "swap -l" reports:

# swap -l
swapfile			dev	swaplo	blocks	free
/dev/md/dsk/d20		85,20		16	14889904	14763056
/dev/dsk/c1t0d0s1		32,1		16	8389632	8265120
/dev/dsk/d1t1d0s1		32,9		16	8389632	8264480
/dev/dsk/c1t2d0s1		32,17		16	8389632	8267552
/dev/dsk/c1t8d0s1		32,57		16	8389632	8264816

One last question: is there a kernel parameter that limits the
amount of swap space a system could make use of?

Various people pointed out that if I wasn't running a 64-bit OS,
the greater than 2GB swap spaces would not have been allowed to
be created.  Some sample answers were:

"The 32-bit kernel can use more than 2GB of swap, just not from one
swapfile.  Multiple swapfiles of 2GB or less may be used as you would
expect.  You can limit the size of /tmp to prevent files created there
from consuming all available swap.  See the mount_tmpfs(1m) man page for
the details, the option then goes into /etc/vfstab."

"I am unaware of a swap limiting kernel parameter.
Solaris 2.6, if memory serves, had a 2gb swap limit per disk"

"It is QUITE possible unless you chose to limit the size of /tmp via
a size=, e.g.
  swap  -       /tmp            tmpfs   -       yes     size=200m
that a user or users exhausted all of virtual memory by filling /tmp
with garbage since /tmp and swap (and ram) all share the same
real estate."

-- Darryl

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