Edit: Some links no longer work.
Originally posted August 10, 2010 on AIXchange
Recently I questioned why so many people choose to download .iso images rather than order a set from IBM. Some of you were kind enough to offer your thoughts.
Being able to download these images from IBM is nothing new, (although the capability to download one DVD image as opposed to multiple CD images is a welcome new twist). Back when I first wrote about this, we weren’t yet able to take advantage of virtual optical media. It makes me laugh to go back and read about the gyrations I once went through to use these disk images for anything other than a source file that I would then need to burn to physical media. The method I described in that post didn’t even allow me boot from the images to load the OS; the images could only be used to load the AIX code into a NIM server using the bffcreate command.
In the article I mentioned that I had to download the CDs, then I noted that:
“On Linux, I can simply run:
mount -o loop -t iso9660 filename.iso /mnt/iso
“This mounts my CD image on my filesystem. On AIX, mounting an .iso image is a little more involved. First I created my logical volume, in this case:
/usr/sbin/mklv -y’testlv’ datavg 6
“Then I ran the dd command in order to write the contents of the .iso file to my logical volume:
dd if=/aixcd1.iso of=/dev/testlv bs=10M
“Then I mounted my .iso image with:
mount -v cdrfs -o ro /dev/testlv /mnt/iso
“At this point the CD was mounted, and I could run smitty bffcreate.”
Of course these days, with virtual optical media, .iso images can be copied into a virtual media library and loaded and unloaded without the need to create logical volumes and run dd commands.
Another thing that simplifies this process now is the addition of the loopmount command in AIX. Anthony English explains:
“You can now mount ISO images directly onto an AIX LPAR using the loopmount command. This was introduced into AIX 6.1 TL 4 (use the oslevel -s to check your current level). The man page for loopmount provides this example:
loopmount -i cdrom.iso -o “-V cdrfs -o ro” -m /mnt
So, with all this said, I can certainly understand why people choose to download the .iso images, and that for some in fact it may be their only option. As one reader told me: “I prefer the downloads. It seems easier to me to mount an .iso via virtual means. Though we keep hard copies at the DC just for the reasons you mention.”
Not everyone disagreed with me though. Here’s another comment: “Call me old school also, but I too like for IBM to send me the base media, comes in real handy for booting to maintenance mode for an outage recovery. I can always download/burn .iso (images), but if a server is down, every minute counts….”
Here’s a final comment I liked: “I wish I could download .iso images, because I have more often access to a high bandwidth Internet connection than to a physical media drive. (I work on some systems that are a several miles away from me.)” Without physical access to a machine, an .iso image in a virtualized machine is certainly the way to go. But even in that situation, I’d still want a copy of the media from IBM as well.
Yes, I understand that we can boot from .iso images as if an actual DVD was loaded in a virtual drive. We can also burn our own copies from the images if we want to. With physical media, we can still load our system even if the environment lacks a NIM server or we don’t have a VIO server running on the server in question. Each method has its pros and cons. As in any case, we need to know what tools we have at our disposal, and then use the most appropriate one for the task at hand.
On an unrelated note, the Central Region Virtual users group hosted another great session — this one covers NIM. Check out the replays (here and here) and download the materials (here and here).