Xen users - Aug 2013 - Best Practice and Documentation for Xen 4.2 using LibXL

Hi,

I''m getting back in to Xen after a little while out of the game.  It
seems
things have moved on quite a bit while I was away!

I remember using "xm list" and "xm migrate --live" etc to
manage my VMs but
I recently took a look at what I believe to be the latest stable release
(Xen 4.2) and found that xm is deprecated and I should be using xl instead. 
When I try and do things with xl it seems to conflict with xend.  Sorry I
can''t be more specific -my test setup is a bit of a mess now.
It seems that whenever I google for a Howto or Faq it invariably shows me
the xm way of doing things, and the documentation on Xen 4.2 seems to be not
as comprehensive as Xen 3 was.
Can anyone point me to a definitive guide for Best Practice with Xen 4.2
running Centos 6, e.g. examples of tried and tested config files which work
out of the box so I can create my VMs straight away.

As a minimum what I need to do is get to the point where I can easily do the
following:

create a VM using a config file which defines its name,ram,cpus,etc, and
points to an LVM partition i''ve just created, and builds Centos from an
ISO
I have on the Dom0.

I have managed to get this working partially using virt-install but that
seems to use XML config and not the XL-style configs.

When I build a config file using the examples at 
http://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html and 
http://xenbits.xen.org/docs/4.3-testing/misc/xl-disk-configuration.txt 
I get nowhere when I try "xl create <my-config-file>".  It says
it is
building the VM then I just get a couple of DEBUG messages and the VM
disappears.

I just need to understand the best toolset and config combination to use
because from what I have done so far this is not looking like a stable
enough environment for production.

Hope someone can help.

Regards,
GW








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On Tue, 2013-08-27 at 13:56 -0700, Virtually Mad wrote:
> Hi,
> 
> I''m getting back in to Xen after a little while out of the game. 
It seems
> things have moved on quite a bit while I was away!
> 
> I remember using "xm list" and "xm migrate --live" etc
to manage my VMs but
> I recently took a look at what I believe to be the latest stable release
> (Xen 4.2) and found that xm is deprecated and I should be using xl instead.
> When I try and do things with xl it seems to conflict with xend.
Yes, you need to stop xend from running, otherwise bad things will
happen (like your xl domains getting immediately shot, as you''ve
experienced).

xl includes a latch to warn you if xend is running and refuse to operate
unless forced to. Not sure why that isn''t working for you (I assume it
isn''t because you haven''t mentioned it).

>   Sorry I
> can''t be more specific -my test setup is a bit of a mess now.
> It seems that whenever I google for a Howto or Faq it invariably shows me
> the xm way of doing things, and the documentation on Xen 4.2 seems to be
not
> as comprehensive as Xen 3 was.
I''m not sure what you mean, if anything there is far more (and better)
documentation for Xen 4.2 than there ever was for previous versions.
Perhaps you are referring to 3rd party guides?
> Can anyone point me to a definitive guide for Best Practice with Xen 4.2
> running Centos 6, e.g. examples of tried and tested config files which work
> out of the box so I can create my VMs straight away.
xl is intended to be command line and config file compatible with xm
(with one or two caveats mentioned in http://wiki.xen.org/wiki/XL). I
think your problems stem from xend interfering.

If you still have problems when xend has been stopped (and even better
if you can prevent it starting on boot and restart) then please let us
know. You will gain more traction if you include the logs which are
requested in http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen .

Ian.

Ian Campbell-10 wrote
> On Tue, 2013-08-27 at 13:56 -0700, Virtually Mad wrote:
>> Hi,
>> 
>> I''m getting back in to Xen after a little while out of the
game.  It
>> seems
>> things have moved on quite a bit while I was away!
>> 
>> I remember using "xm list" and "xm migrate --live"
etc to manage my VMs
>> but
>> I recently took a look at what I believe to be the latest stable
release
>> (Xen 4.2) and found that xm is deprecated and I should be using xl
>> instead. 
>> When I try and do things with xl it seems to conflict with xend.
> 
> Yes, you need to stop xend from running, otherwise bad things will
> happen (like your xl domains getting immediately shot, as you''ve
> experienced).
> 
> xl includes a latch to warn you if xend is running and refuse to operate
> unless forced to. Not sure why that isn''t working for you (I
assume it
> isn''t because you haven''t mentioned it).
> 
> 
>>   Sorry I
>> can''t be more specific -my test setup is a bit of a mess now.
>> It seems that whenever I google for a Howto or Faq it invariably shows
me
>> the xm way of doing things, and the documentation on Xen 4.2 seems to
be
>> not
>> as comprehensive as Xen 3 was.
> 
> I''m not sure what you mean, if anything there is far more (and
better)
> documentation for Xen 4.2 than there ever was for previous versions.
> Perhaps you are referring to 3rd party guides?
> 
>> Can anyone point me to a definitive guide for Best Practice with Xen
4.2
>> running Centos 6, e.g. examples of tried and tested config files which
>> work
>> out of the box so I can create my VMs straight away.
> 
> xl is intended to be command line and config file compatible with xm
> (with one or two caveats mentioned in http://wiki.xen.org/wiki/XL). I
> think your problems stem from xend interfering.
> 
> If you still have problems when xend has been stopped (and even better
> if you can prevent it starting on boot and restart) then please let us
> know. You will gain more traction if you include the logs which are
> requested in http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen .
> 
> Ian.
> 
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@.xen
> http://lists.xen.org/xen-users
Thanks Ian.  Can''t supply the logs as due to time constraints have had
to
give up on XL and just get something working with libvirt.  I was having
problems with finding an xl config syntax that worked for me, specifically
the disk and iso definitions were not intuitive and I kept getting errors
with devices not being found and root disk not found and a few other errors. 
But libvirt works fine, and I''ll revisit XL when I get a chance.
As for the docs, I probably was remembering the excellent Red Hat
Virtualisation Guide and Oracle VM Install Guides etc. but there was a
100-page PDF for Xen 3 and I couldn''t find anything on Xen 4 other than
man
pages, and a wiki with mostly plain text files etc. e.g. the xl-disk-config
info which I tried and failed to use for my disk config.

GW




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