最近在配置多台使用RHEL5
X86_64的虚拟机，由于要做门户开发的实验。发现一个奇怪的现象：VMware中的RHEL5经常停止在Starting
udev阶段，由于时间有限没有等太长时间，一般几分钟没响应我就reset了。这时重启几次虚拟机或者修改一下虚拟机的配置，比如改成单cpu单核心启
动就又成功了。今天终于发现了原因：

Clocksource is the name of the new timekeeping
subsystem introduced in the Linux 2.6.18 kernel. In this subsystem
there are several clocksources that can be used to read the time. One
of them is the tsc clocksource which
uses the Time Stamp Counter that is present on each processor and can
be used to track how much time has elapsed. The TSCs on the different
processors are not necessarily perfectly in sync with each other, so
time can appear to go backward if the TSC is read on one processor and
then another processor. Early versions of the tsc
clocksource did not handle this case, which can lead to the guest
operating system not responding. Due to the different timing behavior
of running in a virtual machine, this can be observed more frequently
in a virtual machine.

所以如果遇到这种情况，只需要修改CPU为单CPU，启动系统后编辑/etc/grub.conf，在对应kernel的启动项后加入对应系统的参数即可。

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1007020
http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1006427