Re: [Xen-API] Issues with XenAPI on CentOS 6.3

[Dave Scott <Dave.Scott@xxxxxxxxxxxxx>]

Hi John,

This is really, really odd!

If you're in the market for a workaround, you could use the 
"execute_command_get_output" function to run "cat filename" -- ugly but it has 
to work.

 let stdout, stderr = Forkhelpers.execute_command_get_output "/bin/cat" [ 
filename ] in
...

Cheers,
Dave

> -----Original Message-----
> From: John Garbutt [mailto:John.Garbutt@xxxxxxxxxxxxxxx]
> Sent: 11 March 2013 12:46 PM
> To: Dave Scott; 'John Garbutt'; Mike McClurg
> Cc: xen-api@xxxxxxxxxxxxx
> Subject: Re: [Xen-API] Issues with XenAPI on CentOS 6.3
> 
> Hi,
> 
> Thanks for talking a look :-)
> 
> The original code was using Unixext, and had the same errors, from what I
> remember.
> 
> I tried with 3.12.1 and 4.00.1 and have got the same errors.
> 
> I am guessing the issue is specific to the CentOS kernel of 3.4.x? Don't 
> really
> have any sound reasons why though.
> 
> It is interesting that the standalone code seems to work perfectly, and I can
> cat the file, but when running inside the xapi deamon, it fails.
> 
> John
> 
> On 11/03/2013 12:36, "Dave Scott" <Dave.Scott@xxxxxxxxxxxxx> wrote:
> 
> >Hi,
> >
> >In the broken strace, I can't explain the different sequence of
> >syscalls between the file that works (lstat; open) and the file that
> >doesn't (lstat; stat; access; open). I also can't reproduce the
> >behaviour you see on my Ubuntu with ocaml 3.12.1. Out of curiousity,
> >which ocaml version are you using?
> >
> >However this is the second time recently we've been bitten by unwanted
> >behaviour in the buffered I/O channel code. Since we're dealing with
> >low-level stuff like sysfs 'files' where the behaviour of file I/O may
> >not exactly match that of regular files, I recommend that we drop down
> >to the low-level Unix.* functions which map directly onto syscalls.
> >
> >Assuming these sysfs files only contain one line of text anyway, how
> >about replacing
> >
> >    read_one_line file
> >
> >with
> >
> >    Unixext.string_of_file file
> >
> >Cheers,
> >Dave
> >
> >> -----Original Message-----
> >> From: xen-api-bounces@xxxxxxxxxxxxx [mailto:xen-api-
> >> bounces@xxxxxxxxxxxxx] On Behalf Of John Garbutt
> >> Sent: 07 March 2013 3:03 PM
> >> To: Mike McClurg
> >> Cc: xen-api@xxxxxxxxxxxxx
> >> Subject: Re: [Xen-API] Issues with XenAPI on CentOS 6.3
> >>
> >> Hey Mike,
> >>
> >> Still stuck with these permissions issues when running XAPI on CentOS
> >>6.3
> >>
> >> I have extracted some strace from a standalone OCAML program that
> works:
> >> https://gist.github.com/JohnGarbutt/5108513
> >>
> >> I have hacked up XAPIs ballon.ml, there the permissions error occurs,
> >>to use  the above code. The same code as above, when running as part
> >>of XAPI, was  able to read my test file, but was unable to read
> >>/sys/devices/system/xen_memory/xen_memory0/info/current_kb
> >>
> >> I have managed to capture the strace here, by adding the "-nowatchdog"
> >> param to xapi:
> >> https://gist.github.com/JohnGarbutt/5108563
> >>
> >> Any ideas welcome!
> >>
> >> John
> >>
> >> On 1 March 2013 19:37, Mike McClurg <mike.mcclurg@xxxxxxxxxx> wrote:
> >> > On 01/03/13 17:43, John Garbutt wrote:
> >> >>
> >> >> I installed xenopsd using OPAM, not sure how to get hold of the
> >> >> associated code to check what it is doing.
> >> >
> >> >
> >> > You're probably using the opam remote
> >> > 'github.com/xen-org/opam-repo-dev/',
> >> > which tells me...
> >> >
> >> > https://github.com/xen-org/opam-repo-
> >> dev/blob/master/packages/xenopsd.
> >> > 1.0.0/url
> >> >
> >> > ... that the xenopsd repo you've installed is here:
> >> >
> >> > git://github.com/djs55/xenopsd.git
> >> >
> >> > I'll take a look at your other run-time issue now.
> >> >
> >> > Mike
> >>
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