guest machines falls behind time
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
kvm (Ubuntu) |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
Binary package hint: kvm
We have seen that guest machines can fall considerably behind wall clock time. This is apparently a well know phenomenon with virtual machines, and is the subject of a VMware whitepaper (http://
In this whitepaper, it is stated that running NTP guest machines is not a good idea, and it is reasonable to imagine that the NTP server would go crazy when the clock constantly is lagging.
A better solution is to have a cron script that runs regularly, updating the time to the value of the host's hardware clock.
We are running with Ubuntu JeOS, where NTP is a required package. For the above reasons, this is not a good idea. A package containing a time synchronizing cron script is a much better solution. Ubuntu JeOS should ship with such a package.
Another solution (?) could be a modification to KVM, so its virtual clock device would be tied to the host clock.
Details:
Host machine runs Ubuntu server 7.10.
kvm is a locally back-ported hardy package: QEMU PC emulator version 0.9.0-cvs (kvm-59)
The problem does not exist when the host runs hardy and the newest version (061) of kvm and the kernel module.