Virtualization

[Kent Borg]

Victor Padro wrote:
> I am looking for a virtualization software, which can be used of 
> course in ubuntu, and in a daily basis, under a production enviroment, 
> i have used vmware server and workstation under windows for some 
> years, and i like it a lot, but now i am migrating everything to 
> linux, so i need to reduce costs in all terms, and i think 
> virtualization can do the job, so if any of you have used any software 
> in production, using ubuntu or any other distro, i'll be glad to hear 
> from you, thank you all! 

The obvious answer will be "Vmware".  There are versions that are free 
("as in beer") but it is still commercial and not open source (so not 
"free as in speech").  Vmware owns the software, they make you agree to 
their terms, and can possibly revoke your permission to use it.  (Have 
any of us read those terms carefully?  I have not.)

If this is cool with you, then cool.

If you want to have your server under more certain control, there is 
more than one open source alternative.  (Free as in beer and free as in 
speech.)

I recently started using Qemu on my personal basement server.  I have 
Ubuntu 7.04 as the host OS (running NTP and very little else), and 
several Ubuntu 7.04 installations running under QEMU as guests.  It 
works so far.  My virtual mail machine has an uptime of 36 days at the 
moment.

I don't have one of the newer CPUs that support full virtualization.  
But using the kqemu kernel module makes the guests very fast anyway.

One thing I don't have is fancy management tools.  It sounds like they 
are improving quickly, but I was kind of ahead of them and wrote simple 
script files that launch each guest machine with a "serial" console that 
runs in "screen", so I can log into the console as I please, scroll back 
through the boot, etc.  When the host boots the guests come up 
automatically.  I don't have any auto shutdown of the guests set up.

Another drawback is the disk emulation by Qemu is slow.  In my case it 
is fast enough.  And it looks like it will get better.  My host is 
running software RAID 1, so the guests get the benefit of that without 
any fuss inside each of them.

I played with Xen earlier, but the coupling between the host and guest 
software versions is too tight.  Upgrade the host and guests can break.  
They are too intimately linked for my taste.  It is nice to be able to 
upgrade a guest OS with absolutely no interaction with the host 
versions.  The kernel module is a version link between the host OS and 
Qemu, but too terrible: recompile for the new host kernel.  Because 7.04 
didn't have a completely working version of Qemu I compiled Qemu from 
sources myself.  Being just a user space program, it was pretty easy.  
Xen is much more complicated.  Trying to run a mix of versions would be 
a nightmare, and probably impossible with Xen.  Running a mix of Qemu 
versions is no more problem than running a mix of versions of any program.

Because my host OS is running very little, upgrading it should be pretty 
easy.  I expect I will wait until the next LTS version comes out. 

-kb