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xen-users
Re: [Xen-users] Time change conundrum
I've tried messing around with clocksources in both dom0 and domUs
yesterday afternoon,
nothing seemed to make a difference, setting independent wallclock
appears to be impossible
in Xen 4.x, there is no /proc/sys/xen directory nor files within to
set a value in.
Whatever the clocksource, the domu should boot with the current time
from dom0! Which it
doesn't, if you have changed the time in dom0, somewhere dom0 is
maintaining another clock
which seems to be set on boot, and cannot be altered by normal
means.
Niall Fleming BSc. (Hons)
Systems Administrator
Webanywhere Limited
Phone: 0800 862 0131 Ext: 203
Web: http://www.webanywhere.co.uk
Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB
Registered in England with company number 4881346
On 02/11/2011 12:07, Miles Fidelman wrote:
I
was suggesting that you look at it for information about the
parameters that effect
where DomUs get there time from, notably:
xen.independent_wallclock
clocksource=jiffies
There seem to be a number of combinations of what can be set in
both Dom0 and DomU.
I happen to set up all of my machines using the "workaround #1"
configuration, and all
works fine - but one thing I note vis-a-vis your comments is that
the hardware clock
is not accessible from within my VMs
You might want to read the prose under "workaround #3" - and
follow the links - this
prose is particularly suggestive:
"set independent_wallclock to 0 (all domains; VMs will follow
dom0's clock)"
you might, for example, want to check what independent_wallclock
is set to, and where it's being set
Niall Fleming wrote:
As stated I have no issue with drift
whilst running.
It's on DomU boot, the time is not the time that dom0 is set to
if dom0 time was changed after boot.
*Niall Fleming BSc. (Hons)*
Systems Administrator
Webanywhere Limited
Phone: 0800 862 0131 Ext: 203
Web: http://www.webanywhere.co.uk
Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB
Registered in England with company number 4881346
On 02/11/2011 11:39, Miles Fidelman wrote:
First off... take a look at
http://wiki.debian.org/Xen, look for the section on
'clocksource/0: Time went backwards'
Niall Fleming wrote:
Here's a confusing issue for you, I
have a bunch of machines running Xen 4.1.
The time in the BIOS was wrong at machine power on, so
logically, I set the time in
Dom0 with NTP and synced it back to the hardware clock (just
in case). I restart the
VMs which came up before the time changed, so that they
would get the correct time
on startup (as has always worked in the past with Xen 3.x).
The VMs do *not* come up with the initial clock set by the
system clock in Dom0, they
persist in using the time before it was set on the host
system (plus however many
seconds/minutes etc.) have passed, so the original clock
time on Dom0 is ticking along
somewhere even though every utility in the system seems to
report the 'correct' time
as I have set by NTP.
Any ideas? I'm at my wit's end with it, I've tried different
kernels (albeit with [almost] the same
config), both jeremy-git-xen-next-2.6.32 and linux 3.1.0+
(latest from git). I've tried with different
Xen version 4.1.0/4.1.1/4.1.2 and the problem exists in each
of them.
I know that I can run NTP in each VM, but I'd like the
system time to be correct at boot up as it
will make the timestamps in the logs very confusing when it
jumps back an hour.
--
*Niall Fleming BSc. (Hons)*
Systems Administrator
Webanywhere Limited
Phone: 0800 862 0131 Ext: 203
Web: http://www.webanywhere.co.uk
Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21
3BB
Registered in England with company number 4881346
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