Hello Michael,
Am 29.09.2020 um 14:10 schrieb Michael Quigley - Sec <MichaelQuigley@xxxxxxxxxx>:
I've seen a couple articles which cover the process in broad strokes.
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.
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.
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.
(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. ;-)
:wq! PoC
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