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xen-users
Re: [Xen-users] Installing Xen on Debian Sarge
Mark Foster wrote:
Miguel Enrique Cobá Martínez wrote:
2. They are all about installing on plain devices, not lvm volumes.
If you are serious about using Xen for production systems you will want
use LVM or something other than simple file-based disks. Sounds like
some others are using true SANs or gnbd or drbd? My personal preference
is to assign an 8GB logical volume for "/" and another volume for swap,
the size depending on how much RAM will be assigned to the DomU. That
fits my bill, but in the physical world I much prefer giving separate
partitions for /boot, /usr, /var and so on. It's just too much
(maintenance) overhead with virtual systems. I also prefer to use RAID
0+1 over SCSI.
Yes I agree, in my future servers I will be using something more robust
that simple IDE disk. For the moment, as I am starting with Xen, I have
to use my desktop for all the tests. Unfortunately, until I can show a
working system and the advantages for use it, they aren't investing much
money for this :D
I will be testing a distributed system I built for work. For this I need
a central node and 10 remote nodes. I thought that Xen will be the
perfect solution. Just create 11 DomUs with minimal debian in each one,
run the test of the system and collect statistics.
I have put a lot of time in my current desktop, so I would like to
continue using my desktop, but running as Dom0. I would like to use the
second hard drive to install the virtual machines.
I would recommend a dedicated system for Xen Dom0, as running it on your
desktop is asking for trouble. Running your desktop in Xen as a DomU is
also silly.
Keep your Dom0 as small as possible to minimize your risk when patching
(you are patching right?)
Yes they are a lot of trouble. I finally have a Dom0 and three DomU, all
with sarge, but the dom0 nvidia card is quite hard to configure.
After a lot of problems and 3 days of search and testing I finally
booted my machine as Dom0. These are the steps I followed:
1. I used the unstable pkgs for xen
OK.
2. I downloaded the src from:
http://www.cl.cam.ac.uk/Research/SRG/netos/xen/downloads/xen-2.0.7-src.tgz
and compiled using my current kernel config in /boot.
Huh? You used the pkgs AND you installed from src?
Yes, because the packages only install /boot/xen.gz, xend and xendomains
and symlinks in /etc/init.d/. You are supposed to build or download
your dom0 and domU images.
3. I installed the new XenLinux kernel in /boot and configured menu.lst
according.
3. I had to build a initrd image so that the boot process could mount
the root partition on lvm. I use the script from
/usr/share/doc/lvm2/examples/lvm2create_initrd.gz
to build the initrd, as mkinitrd has a bug with lvm root partitions.
Ah, good info!
4. I updated grub to use the initrd and all worked ok.
After that, I had my system running Xen but without graphical setup.
This is not a problem, as I probably could configured correctly with
patience.
I am now ready for creating domains for the real work and I can say that
I have managed to install Xen successfully.
In spite of that, I have the feeling that the solution isn't optimal or
the best.
So, the questions:
- I'm doing this the proper way?
- Is this the intended way of installing Xen?
I mean, should I use my configured and personalised original machine
(postgresql, apache, firefox, thunderbird, /home, etc) on top of Xen as
Dom0 and from time to time to create DomUs for specific task? Or should
I use a minimal debian for Dom0, just for hosting the DomUs and use one
of the DomU as workstation, with all my configuration and selection of
packages inside and the other DomUs for working as needed?
I wouldn't do what you are doing, but to each his own.
- If I use Dom0 for my workstation, I think I will have full control of
all the others DomUs, and I could use them as I wanted. I could access
it with xm console without problems. But if I use one DomU for my
workstation how could I access the other DomUs? With ssh or vnc only?
What happend if I wanted to access the DomO from DomU? I think that I
couldn't do that.
ssh or vnc or whatever! The only thing you lose is console access from
your desktop to the DomUs, but that can be done by ssh-ing to DomO and
'xm console' from there.
- What will pass with the updates of my kernel in Dom0? Will I need to
redo all the steps for configuring my new xen-enabled kernel, creating
an initrd image, compiling nvidia drivers and, when my Dom0 was updated,
then update all of my DomUs?
You can specify a default kernel in /boot/grub/menu.lst you will
sidestep any kernels installed via apt-get (or aptitude)
A don't want to create a flame war, but I would like to hear the
scenarios you used and the decisions you made when configuring Xen.
Also, I would like to read your toughts about your use of Xen.
Using LVM was a good idea. LVM snapshots are also interesting way to
save disk space and have multiple systems based on a common denominator,
but I have yet to get that going. If anyone else has, I'd sure like to
know how to set it up "right".
Good luck.
I think I'll try them soon.
Thanks
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