We would like to understand the true time setting variables that are used by a Linux OS and zLinux guests running under VM.
The discussion is based on the assumption that our Linux will automagically adjust our server time settings when we "Spring forward" on April 6th for the bi-annual Daylight Saving event. Current Configuration We are running SLES 7.0 Distribution. You have two choices initially when installing Linux OS, Local Time(CST) or Universal Time with offset. In our /etc/rc.config we currently have two relevant settings, which are indicative of the current configuration and choices selected when the OS was initially installed. GMT="--localtime" TIMEZONE="America/Chicago" We have our zoneinfo/localtime symlinked to the /etc/localtime. /usr/lib/zoneinfo/localtime -> /etc/localtime Do our current settings truly dictate an automatic time adjustment that will be made on April 6th, or does the flip need to be switched to GMT -u with offset adjusting for our local TimeZone? Hardware Clock ? In the Lintel world you can sync your hardware clock with your system time clock. However, I would like to clearly understand how and if this interrelates with zLinux under VM or if there is any difference amongst the Hardware platforms on how this is managed. On zLinux is there even such a thing as a Hardware clock which equates to a CMOS clock similar to a pc? Do you have to set or sync the System Time clock within VM or does the Hardware clock even exist at all? When running the "hwclock" utility under zLinux to show the hardware clock information it says...."Cannot access the Hardware Clock via any known method". That leads me to beleive that VM is the virtual hardware master and no Hardware clock is accessible to zLinux kernel or accessory programs and is certainly not provided or served up by the VM OS. Or....is this all irrelevant if we just use NTP to automatically sync time on all of our guest systems with our designated time servers? Thanks for your input. -Drew Arthur
