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

[zithro <slack@xxxxxxxxx>]

On 09 May 2023 10:50, Yann Dirson wrote:
> 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 ?
> You can get other examples in
> https://xenbits.xen.org/docs/unstable/misc/xenstore-paths.html#domain-controlled-paths
Thanks, I should pay more attention to headings ;)
From the comparison between the docs and the xe-daemon, I saw some 
inconsistencies.
I decided to post a bug report in TrueNAS bug tracker :
https://ixsystems.atlassian.net/browse/NAS-121872
(It's a bit messy though, /me not proud).
I didn't check if FreeBSD and TrueNAS do some changes from upstream, but 
it may be of interest for Citrix devs too ?
Apologizes in advance for mistakes due to misunderstanding/noobiness.

> > 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.
No prob and happy to help back !
(@Yann: please tell that to your colleague C. Schultz, so he's more 
inclined to lemme write articles for the Xen docs ^_^).
> > 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
Ah yes, understood.
To complete the commit, I found a few other places where "-s" has not 
been removed from "xenstore_client.c", in func "usage()" :
Example for line 97, diff style:
- errx(1, "Usage: %s %s[-h] [-p] [-s] [-R] key [...]", progname, mstr);
+ errx(1, "Usage: %s %s[-h] [-p] [-R] key [...]", progname, mstr);

Same deletions needed for lines: 100, 103, 109, 112, 115.


KR,
zithro/Cyril