Re: Hosting Linux partitions on IBM i

Patrik,

Gott segnen sie!

My apologies for being rather slow at replying. I've started to reply
several times and another interruption happens. I really appreciate your
response. I'll reply in-line below

Danke,
Michael Quigley
Computer Services
The Way international
www.TheWay.org

-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf
Of Patrik Schindler
Sent: Tuesday, September 29, 2020 11:09 AM
To: Midrange Systems Technical Discussion <midrange-
l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Hosting Linux partitions on IBM i

Here it is one more detailed:

https://try-as400.pocnet.net/wiki/File:IVirtualization_-
_IBM_iHost_and_Client_LPAR_Easy_Install_Guide_v5.03_TR7.pdf

I could not find that PDF online anymore, so I put it on my server.

[Michael Quigley]
Excellent link! I've started reading through it. I know IBM added
functionality since this was published, but it seems to still be relevant.

What all of the docs omit is: How to actually boot and kickstart the

install?

Well, put the iso image into an image catalog on the hosting i LPAR,

mount

it and the LPAR firmware will happily boot it.

Also, for watching the boot process, and setting initial configuration,

you'll

need a console, and this is *not* an 5250 console, but a VT100 one.

I'm thinking I have to release some of the memory from our IBM I

partition

before I can allocate any to the Linux partitions.

Of course. And CPU. This is possible at run-time. With a HMC at least.

[Michael Quigley]

We do not have an HMC. :-(

Also, I'm not sure how much memory would be required to run a simple

Linux partition.

If you omit the graphical environment completely (we're talking about a
server, yes?), then you'll be fine with as little as 512 MB. Yes,

Megabytes.

This is completely sufficient for a Linux "doing nothing" besides having

the

basic services running like ssh, ntp, cron/at, postfix (for delivering

output

generated by cron/at), and syslog.

There are ways to see if Linux needs more RAM. The most important is to
watch the output of vmstat 2 while the machine is busy. Watch the si and

so

columns. If they constantly show activity in the low 2-digit range, you

maybe

need to add RAM, soon. (End vmstat with Ctrl-C) If the numbers are three

or

even four digits, add RAM *now*. :-) How much? "depends". I start with
doubling the amount, so I'm safe.
The output of "free" or "top" regarding the total amount of used swap

space

is *not* an indication of lack of RAM! Over hours and days, the kernel

puts

rarely used pages of allocated memory on disk, to free memory for more
buffers.

[Michael Quigley]
Great advice. I'll start with a minimal set up and increase as needed. As
I said, we're not planning on anything very heavy. But we figure we've got
the big POWER9 box and we would like to take advantage of some of the
horsepower.

(As indicated above, our goal is not a high-capacity server. Just
something for primarily our small IT department.)

I'd recommend to give it a go with 1 GB and a disk file with 8 GB for a
minimum install. You can add more disk files later and depending on the
install, either use LVM to add that new virtual disk to the

volume-group, and

in turn enabling you to resize the logical volume(s) where the

filesystems

reside. This is possible at run-time also. If there's no LVM, you need to
prepare the new disk for a part of the directory tree needing space,

copy that

over, prepare /etc/fstab to mount that volume at boot time, and delete

the

old tree. Known candidates are /var or /home. More details on request.

Any advice or a pointer to a detailed explanation of the requirements

would be much appreciated.

Please provide more detailed explanation what exactly you'll run on the
LPARs. :-) Even if I've 25 intense years of Linux experience, my crystal

ball is

still broken. ;-)

[Michael Quigley]
I haven't been able to repair my crystal ball either.

We will host one couple of webpages developed in C#. These help us track
tasks, projects, as well as some data on PCs. The data is all stored in Db2
for I tables. We've been running it on a sandbox Windows server, but we
need to set up development and production environments. We would like these
two environments to look the same and I don't think we have that many
Windows Server licenses to play with. (That and I would like to utilize
more of the capability of the POWER9 box.)

:wq! PoC

PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc


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