On Thu, 23 Apr 2009, Ugo Bellavance wrote: > Mintairov Mihail a écrit : >> Hello All, I have a problem with hwclock on centos 5.3. in xen guest >> environment. >> # hwclock --debug >> hwclock from util-linux-2.13-pre7 >> hwclock: Open of /dev/rtc failed, errno=19: No such device. >> No usable clock interface found. >> Cannot access the Hardware Clock via any known method. yes - this also shows up in the dmesg at boot time in the domU. I noted it when doing LSB testing, as part of their 3.2 suite wanted to tickle the hardware clock. >> So, I'm afraid that I can not change my time by ntp. >> >> In CentOS mailing list I found a thread "hwclock and util-linux on 5.3", >> but there is still no answer and discussion stopped. Maybe someone knows >> the solution of this problem. > > Maybe the clock is sync'd with the host? essentially this is the case -- the host (the dom0) has exclusive write access as to the clock. -- There is intentionally should be no solution to permit a domU to alter the hwclock, as a domU should not be able to affect the domO's clock. To permit a domU to do do so would permit the client to control the master outer ring zero's crontab, atd, and such Kerberos attacks [keeping a ticket in force longer than intended], and more also come to mind, if a arbitrary domU could control the clock - Russ herrold