I am working on a VM SNTP client to get a time correction at IPL and adjust the system time accordingly. It is working on second level, but I have not been able to get system time to try it first level. The code also needs tidying up and more/better comments.
During testing, I updated the time on the running second level system. Updating the VM time on the fly seems to work, but VM was not designed with this in mind, and I have been warned of potentially fatal consequences of doing so, hence the emphasis on doing it at IPL. Dave Jones wrote an SNTP server for VM, available from the VM Download page http://www.vm.ibm.com/download/. > -----Original Message----- > From: Rob van der Heij [SMTP:[EMAIL PROTECTED]] > Sent: Wednesday, September 11, 2002 3:12 AM > To: [EMAIL PROTECTED] > Subject: Re: NTP Clients in a Linux390 server farm? > > At 00:41 11-09-02, Len Thomson wrote: > > >1. There seems to be no nice way to get VM to maintain it's time synch > >2. There seems to be no nice way to get a Linux guest to synch with the > VM > >time > >3. I really don't want NTP clients all popping up at the same time to do > a > >network synch on every virtual server... > > I admit I only briefly looked at the latest code, but afaik > especially with the 'demand timer patch' Linux uses the TOD > to tell time, and I don't recall seeing the drift corrections > applied. This would mean an ntpd cannot adjust time of Linux > running on z/VM, but one might be able to change that. I can > even imagine hwclock to issue SCK instruction to update the > virtual machine's private offset of the VM TOD clock (to > live through a reboot, but not logoff). > My understanding is that the S/390 TOD does not drift much, > but we do have a problem of the operator setting time on VM > by looking on his $10 Mickey Mouse watch. > > You're very right that you dont't want them all to measure > time separately by talking to some remote ntpd. Howerver, I > did see there is a lot of smartness in ntpd to increase the > time between probes when it finds there is little drift. You > could imagine one local ntpd to talk to a few good clocks, > and have your local systems use that single server. > > It's on my list of things to do, so I would be interested in > what others do (that is the fastest way these days for things > from my list to get done ;-) > > Rob
