topic Re: mkboot for mirroring boot disk in Operating System - HP-UX

mkboot for mirroring boot disk

Shahril M — Mon, 16 May 2005 02:54:32 GMT

Hi folks,

I have done my research on this and found various versions for the mkboot command. I am wondering how they are different, if at all. Note that this is for a 10.20 system, although I wonder if there is any difference on 11.x?

Here are the 4 common versions I found:
"hpux -lq"
"hpux -lq /stand/vmunix"
"hpux -lq (;0)/vmunix"
"hpux –lq (;0)/stand/vmunix"

I also understand I need to -lq the primary disk to protect against the scenario where the secondary is down. What AUTO string should be used for the primary disk?

TIA.

Rgds,
Shahril

Re: mkboot for mirroring boot disk

Naveej.K.A — Mon, 16 May 2005 03:38:29 GMT

Hi,

lifls -l /dev/rdsk/c1t6d0
will give you the list of the files in the lif volume which contains AUTO (which is a file in the lif volume)

The file contains the name of the secondary loader (which is by default hpux)and also the arguments which has to be passed along with the loader (like -lq -lm ,etc)

hpux with the options then loads the kernel.

Regards,
Naveej

Re: mkboot for mirroring boot disk

Victor Fridyev — Mon, 16 May 2005 05:02:04 GMT

Hi,

Look at the attached script, I use it for mirroring of system disks.

HTH

Re: mkboot for mirroring boot disk

Pete Randall — Mon, 16 May 2005 05:09:00 GMT

Shahril,

Those are four slight variations of essentially the same command. The first assumes defaults , the second gets slightly more specific and so on, but they all essentially do the same thing.

Here is an extract from my standard Mirroring notes:

3. Use mkboot to place the boot utilities in the boot area and add the AUTO file
"mkboot /dev/rdsk/c1t6d0"
"mkboot -a "hpux -lq" /dev/rdsk/c1t6d0"

4. Use mkboot to update the AUTO file on the primary boot disk
"mkboot -a "hpux -lq" /dev/rdsk/c0t6d0"

That's all you really need.

Pete

Re: mkboot for mirroring boot disk

Naveej.K.A — Mon, 16 May 2005 05:16:16 GMT

Shahril,

If i have not mistaken your question,

"hpux -lq"
"hpux -lq /stand/vmunix"
"hpux -lq (;0)/vmunix"
"hpux -lq (;0)/stand/vmunix"

I don't find any issues with 1,2 and 4, but really doubt if the third one will work!!!

The best way would be to use the first one.
hpux -lq.

Regards,
Naveej

Re: mkboot for mirroring boot disk

Uli Manschke — Wed, 25 May 2005 08:22:28 GMT

Hi,
I'll try to remember my trainer time ...
let's split up the command.

The full thing would be:

ISL> hpux -lq boot (8/8/0.3.0;0)/stand/vmunix

Here are the parts of it:

ISL
is a command interpreter which has some internal commands. It understands the LIF (Logical Interchange Format) filesystem format, a very basic thing which specifies file locations by distance from the first block. Inside this LIF filesystem is (hopefully, at least :-) one "file" called "hpux" (there may be more, e.g. "ODE", Offline Diagnostic Environment).

hpux
is a file residing inside the LIF filesystem part of the boot disk. It knows about the HFS filesystem structures and thus is able to read the kernel file from the /stand filesystem.

-lq
an option for the hpux command. "lq" stands for "low quorum". The quorum rule of LVM requires that MORE than 50% of the VG's disk are available at boot time. If there are only 50% or less disks of the root VG available, the quorum rule can be turned off with "-lq". In most cases, the root VG consists of only two disks - if one fails, there are exactly 50% of the root VG disks available and the quorum is not reached. If you have three disks in the VG, the system would perfectly boot if one fails - if all required filesystems (etc) are found on the remaining disks.

boot
directs the hpux command that we want to boot the system. "boot" is the default, it may be omitted. There are more commands available, e.g. "ls" : the hpux command has the ability to do the same as the UNIX command "ls". So, "hpux ls (;0)/" gives you a directory listing of the HFS on LVOL1.

(8/8/0.3.0
specifies the disk device on which the "hpux" command should look for the kernel file. Well, since a cross-device boot is not possible, it's useless to specify anything else than the disk where the ISL and hpux command are loaded from. So, in nearly all cases, this part is left out, falling back to the disk we started from.

;0)
specifies the disk SECTION to start from. Some years ago (before we got the blessings of LVM), disks were hard-sectioned in areas 1 - 15. This isn't used any more, I suppose ... When using LVM, the section is always 0. This is the default, so it can be omitted.

/stand/vmunix
is the name of the kernel to load. Actually, the directory part "/stand" needn't to be specified, since the "hpux" command searches the HFS filesystem on LVOL1 which is later mounted to /stand - in fact, the kernel file's absolute path on that LVOL1 filesystem is "/vmunix" :-) The boot process normally uses LVOL3 as / (root) and then mounts LVOL1 to /stand - so the file vmunix is in the top layer directory of LVOL1 filesystem. The human insanity "remembers" the file's name from the running (= mounted) system, i.e. /stand/vmunix, so the programmers adapted to our dumbness and allowed to put /stand in front of the file's name. The default for this thing is "/stand/vmunix" - it can be omitted.

So ... there are lots of defaults:

hpux -lq
hpux -lq boot
hpux -lq boot (;0)
hpux -lq boot (;0)/stand/vmunix
hpux -lq boot (;0/vmunix

all do the same ... read the kernel file from LVOL1 :-)

Regards
uli

Re: mkboot for mirroring boot disk

Shahril M — Wed, 25 May 2005 19:35:33 GMT

Hi Pete,

Thanx for your reply.

You mention the first one assumes defaults. What are the defaults and under what known circumstances would either one of the other 3 be used instead?

Referring to my second question, you also recommend to -lq the primary disk. Is this to allow boot up from this disk should the secondary be down?

Rgds,
Shahril

Re: mkboot for mirroring boot disk

Shahril M — Wed, 25 May 2005 19:38:12 GMT

Hi Uli,

An excellent and comprehensive answer, thanx.

A perfect 10 reply if not for missing out my 2nd query. Well, I hold the points till then.

TIA,
Shahril

Re: mkboot for mirroring boot disk

Devender Khatana — Wed, 25 May 2005 20:56:18 GMT

Shahril,

HPUX is the secondry loader what load the kernel with the arguments set in the AUTO file. If -lq option is set on any disk means that quorum check will be bypassed on the root VG causing it to boot from only a single disk even if VG has originally two disks. This can be set on both primary as well as secondry disk to byepass check for the other one.

Option 1 , 2 & 4 will achive the same task.
Option 3 will not work as kernel has to be there in /stand always and can not be there in root.(/)

HTH,
Devender

Re: mkboot for mirroring boot disk

Thayanidhi — Thu, 26 May 2005 01:44:33 GMT

Hi,

-lq with both disks = Any disk failure will not stop the booting.

-lq only in alternate boot disk = If secondary fails system will not boot. If primary fails system boots.

no -lq in both disks = any disk failure system will not boot(not recommended)

It's upto you to desire!

I suggest to set -lq in both disks, and do a regular check on the VG status for synchronization.

You were asking about the defaults.
The default disk is the disk which runs ISL
The default section is 0 (lvol1)
The default kernel is /stand/vmunix

Note that even if -lq is not set you can manually boot the system by interacting with ISL and give manually "hpux -lq"

Regds
TT

Re: mkboot for mirroring boot disk

Uli Manschke — Thu, 26 May 2005 03:08:24 GMT

Well, then I'll try to earn my points :-)

Whether and where to use -lq in the AUTO string depends on what you want the system to do in case of a disk failure.
Assuming the boot disk is mirrored, thus the root VG consists of exactly two disk.
-lq tells the hpux command to ignore the quorum rule, thus : whenever -lq is found, the system will try to automatically boot even if not all disks are physically available.
So, the choices you have are:
1. no lq option on any disk
2. lq option set only on the primary disk
3. lq option set only on the secondary disk
4. lq option set on both disks.

What happens?
1. If any of the disks is not available, the system will stop booting automatically. But you are still able to manually boot with
boot pri/alt IS
hpux -lq
2. If the secondary disk is unavailable, the sytem will boot automatically. If the primary disk fails, the system will stop booting; again, you can manually boot as in 1.
3. like 2., but with primary and secondary swapped.
4. The system will boot automatically, whichever disk fails.
Just to mention :-) ... if both disks are unavailable the system will not boot ... irrespective of the existence of the lq option :-)

So, the normal settings are either

hpux -lq (boot whenever possible)
or
hpux (boot only if both root VG disks are available)

on all disks of the root VG, depending on what you want the system to do in case of a missing disk.
I've very rarely seen different strings on the disks - the option is meant to allow system availability even if one disk fails.

That one disk is missing will be automatically recorded in "dmesg" output, which generally is also logged in syslog.log.
So, if you do system monitoring with really good tools like OpenView Operations (well, I must admit - I'm in OpenView Sales :-), they will send you a warning.

HTH :-)
uli