UML->Xen laundry list

UML->Xen laundry list

[Matthew Bloch]

Hello,

I'm nearly finished converting our hosting scripts (in Ruby) to work 
with Xen as well as UML so wondered whether I could solicit some 
miscellaneous comments on my remaining jobs.   I appreciate there may be 
(yet) no official way to do any of these, but I'd appreciate pointers to 
the relevant bits of source or any other relevant discussion.  The 
reason is I'm keen to make a few hacks to the user-space tools to better 
integrate with our existing scripts, not because I'm just poking around 
in lower level interfaces for fun (though I am having fun :) ).

How to send a Ctrl+Alt+Delete (or sysrq) to a XenLinux guest kernel?

How to create a vif interface from dom0, supply it pre-configured to a 
domain?

Disc synchronisation: when specifying a block device as a file: from a 
Linux domain 0, does the back-end driver in dom0 cache disc writes from 
other domains?  i.e. if power is lost, could the journalled filesystems 
in other domains become corrupted?  I'm guessing the answer is "no" but 
this is just one of those avoidable hazards of UML that I wish to avoid 
again if possible.

Where in the libxc C interface can I find the name of a domain?  I know 
I probably shouldn't be using this interface, I'm just curious.  (there 
must be a better way than grovelling around in /var/xen)

Finally any docs on the sxp libraries: purpose and formats would be 
greatly appreciated.  I assume it's a light cross-language data 
serialization library but haven't dug very deeply yet.

cheers,

-- 
Matthew



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Re: UML->Xen laundry list

[Mike Wray]

Matthew Bloch wrote:
> Hello,
> 
> I'm nearly finished converting our hosting scripts (in Ruby) to work 
> with Xen as well as UML so wondered whether I could solicit some 
> miscellaneous comments on my remaining jobs.   I appreciate there may be 
> (yet) no official way to do any of these, but I'd appreciate pointers to 
> the relevant bits of source or any other relevant discussion.  The 
> reason is I'm keen to make a few hacks to the user-space tools to better 
> integrate with our existing scripts, not because I'm just poking around 
> in lower level interfaces for fun (though I am having fun :) ).
> 
> How to send a Ctrl+Alt+Delete (or sysrq) to a XenLinux guest kernel?
> 
> How to create a vif interface from dom0, supply it pre-configured to a 
> domain?

At the moment you can't - the vif interfaces in dom0 are created by
the back-end network drivers. You could modify /etc/xen/scripts/vif-bridge
or configure a different script if you need to do stuff to the vif.

> 
> Disc synchronisation: when specifying a block device as a file: from a 
> Linux domain 0, does the back-end driver in dom0 cache disc writes from 
> other domains?  i.e. if power is lost, could the journalled filesystems 
> in other domains become corrupted?  I'm guessing the answer is "no" but 
> this is just one of those avoidable hazards of UML that I wish to avoid 
> again if possible.
> 
> Where in the libxc C interface can I find the name of a domain?  I know 
> I probably shouldn't be using this interface, I'm just curious.  (there 
> must be a better way than grovelling around in /var/xen)

You can't. Xen doesn't know the names of domains (well not the full names
anyway), only xend knows what the domain names are.

> 
> Finally any docs on the sxp libraries: purpose and formats would be 
> greatly appreciated.  I assume it's a light cross-language data 
> serialization library but haven't dug very deeply yet.

It's documented in docs/misc/xen_config.html (and possibly elsewhere).
Basically it's a lisp coding of xml.

Mike


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