Re: xen daemon situation

[Harry Waddell <waddell%caravaninfotech.com@localhost>]

On Wed, 2 Jan 2013 09:25:04 +0100
Roger Pau Monné <roger.pau%citrix.com@localhost> wrote:

> On 02/01/13 07:32, Aaron J. Grier wrote:
> > I find myself falling further down the xen rabbit hole and am still a
> > bit confused as to what xen-related daemons are necessary under what
> > conditions.
> > 
> > I seem to only be able to get things working with (o)xenstored, xend,
> > xenconsoled, and xenbackendd running, even when only using xl.
> 
> Having xend running while using xl can cause all sort of strange issues.
> 

I think as long as you never use xm to manage a domain, things go as they 
should, 
even with xend running. It takes some discipline, especially when I still have 
many systems that use xm. If I wasn't updating these systems a lot, I'd just 
remove xm, but since I am updating them, I can't get used to relying on that. 
Now that I've been doing this for a while, I find that I instead keep 
accidentally trying to using xl on the old systems. 

> > 
> > my understanding is that xend and xenbackendd are deprecated and if I'm
> > only using xl, I should only need (o)xenstored and xenconsoled running.
> > is this correct?
> 
> Yes, xl only needs xenstore and xenconsole.
> 
> > 
> > if I don't run xend, my dom0 name shows up as (null) instead of
> > Domain-0, 
> 
> Dom0 name is set by xencommons init script.

I'm running with the following in rc.conf:

xencommons=YES
xend=YES
xenwatchdog=YES
xendomains_config="/usr/pkg/etc/xen/conf/%s"
xendomains_prehook="/usr/pkg/etc/xen/conf/%s-pre"
xendomains="...

and so long as I only use xl, things work. That said, I'm really looking 
forward to 
xen 4.2 in pkgsrc when everything will be sorted out with xl. 

> 
> > and if I don't run xenbackendd, devices don't get attached to
> > the back end in the dom0, even if I create domUs with xl.  is this
> > something send-PR-worthy?
> 
> What version of Xen are you using? xl is only supported on NetBSD
> starting with 4.2.
>

I've always used the xendomains startup script and with 4.1.3, it contains the 
following:

ctl_command="/usr/pkg/sbin/xl"

so when I first upgraded, I just naively assumed that was what I was supposed 
to use, setup xl.conf, etc.. and found a combination of things that got me 
working again with xl. 

If xl isn't really supported, then the xendomains rc script probably shouldn't 
be using 
it. 
 
> > 
> > what does xenwatchdogd do, anyway?  I can't seem to find any
> > documentation on it, and asking takes less of my time than crawling
> > through the source code...  :)
> 
> xen watchdog is used to check a list of DomUs to see if they are
> running, so you can perform automatic actions when a DomU crashes. I've
> never used this, so I'm afraid I don't know whether the code works or not.
> 


I use it and have no idea if it works or not, which I guess is a good sign. :-)


Thanks, 

Harry Waddell