There have been some very good ideas posted here on the hows and whys of having a shared Linux kernel.
Some caveats, however:
1) the example Rexx code to create and save a Linux kernel in a NSS only works for 2.4.x level kernels, in 31-bit mode. It does not work with the newer 2.6.x level kernels at all. 2) The same with the basevol/guestvol approach for sharing DASD r/o. It only works with the 2.4.x level distributions and not the 2.6.x level ones, due to differences in how /dev/dasd is handled.
Linux needs the ability to save itself into a NSS the same way CMS and GCS know how to save themselves (i.e., IPL 190 CLEAR PARM SAVESYS CMS...) I think that there's an effort underway inside IBM do add this functionality to the kernel and get it accepted into the standard source code tree.
DJ
Mrohs, Ray wrote:
Kernel sharing would be a nice-to-have feature. There just seem to be a lot of issues surrounding it's implementation. They involve extensive bootup customizations, r/o and r/w switching, and non-standard manipulations of file systems. Ask five people how to do it and you will get five different solutions. Some are really elegant but they look difficult to undo if your needs change, or if part of your penguin farm has to stay back-level for compatibility reasons. But there needs to be a standardized, supportable way to do this to allow everyone to leverage this important advantage.
For now, the real beauty of Linux on VM, which I saw from the very beginning, is the ability to quickly restore your production environment at the DR location. Put another way, which would you rather recover: 100 1U servers with their disks/SAN(s) and network infrastructure, or 1 or 2 mainframe partitions?
Ray Mrohs Energy Information Administration U.S. Department of Energy
-----Original Message----- From: Noll, Ralph [mailto:[EMAIL PROTECTED] Sent: Wednesday, January 26, 2005 11:00 AM To: [email protected] Subject: Re: Having 1 linux kernel
That's ok... Don't mind each linux guest having r/w to /usr..../opt.... Just want 1 place to upgrade the kernel... If not might as well have 1u servers.
Ralph
-----Original Message----- From: Adam Thornton [mailto:[EMAIL PROTECTED] Sent: Wednesday, January 26, 2005 9:34 AM To: [email protected] Subject: Re: Having 1 linux kernel
On Jan 26, 2005, at 8:39 AM, Noll, Ralph wrote:
Is there any doc on setting up 1 linux kernel and all linux guests booting from That 1 kernel...
Right now I have 8 linux guests all with separate boot disks...
Be nice to have just one..
You can put the kernel in NSS and then everyone can IPL that shared segment, but that doesn't really get you around needing some per-machine unique r/w DASD. Although with a shared kernel in NSS and smart use of basevol/guestvol, you could probably get a system with minimal writeable DASD.
http://www.vm.ibm.com/linux/linuxnss.html tells you how to do the NSS trick. Ignore the "64M is recommended" bit; I've done it successfully in 12M. Do it in the smallest size you're ever going to want to run with.
Adam
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