Re: xenstored: EACCESS error accessing control/feature-balloon 1

[Yann Dirson <yann.dirson@xxxxxxxx>]

On 5/4/23 20:04, zithro wrote:
> On 04 May 2023 17:59, Yann Dirson wrote:
>>
>> On 5/4/23 15:58, zithro wrote:
>>> Hi,
>>>
>>> [ snipped for brevity, report summary:
>>> XAPI daemon in domU tries to write to a non-existent xenstore node in
>>> a non-XAPI dom0 ]
>>>
>>> On 12 Apr 2023 18:41, Yann Dirson wrote:
>>>> Is there anything besides XAPI using this node, or the other data
>>>> published by xe-daemon?
>>>
>>> On my vanilla Xen (ie. non-XAPI), I have no node about "balloon"-ing
>>> in xenstore (either dom0 or domU nodes, but I'm not using ballooning
>>> in both).
>>>
>>>> Maybe the original issue is just that there is no reason to have
>>>> xe-guest-utilities installed in this setup?
>>>
>>> That's what I thought as I'm not using XAPI, so maybe the problem
>>> should only be addressed to the truenas team ? I posted on their forum
>>> but got no answer.
>>> I killed the 'xe-daemon' in both setups without loss of functionality.
>>>
>>> My wild guess is that 'xe-daemon', 'xe-update-guest-attrs' and all
>>> 'xenstore* commands' are leftovers from when Xen was working as a dom0
>>> under FreeBSD (why would a *domU* have them ?).
>>
>> That would not be correct: xenstore* are useful in guests, should you
>> want to read/write to the XenStore manually or from scripts;
>
> Didn't know that, can you give some use cases (or URLs) for which it 
> is useful, with or without XAPI ?
> I've read xenstore* man pages and could not infer a use case.
> Although I may already see some : updating ballooned memory values, or 
> as Julien Grall pointed out, updating "feature-s3/4" values ?

You can get other examples in 
https://xenbits.xen.org/docs/unstable/misc/xenstore-paths.html#domain-controlled-paths

>
> PS: small mistake in "man/xenstore-write.1.html" (from at least 4.14, 
> and onward), the synopsis reads "xenstore-read" ieof "xenstore-read".
Patch sent, thanks.
> Also, the -s option disappeared from unstable, although it may be 
> expected. I don't know it's purpose either.

See 
https://github.com/xen-project/xen/commit/c65687ed16d2289ec91036ec2862a4b4bd34ea4f

Best regards,

-- 
Yann Dirson | Vates Platform Developer
XCP-ng & Xen Orchestra - Vates solutions
w: vates.tech | xcp-ng.org | xen-orchestra.com



Yann Dirson | Vates Platform Developer

XCP-ng & Xen Orchestra - Vates solutions
w: vates.fr | xcp-ng.org | xen-orchestra.com