User`s guide

Advanced Tasks 185
Changing System Time From
Container
Normally it is impossible to change the system time from a Container. Otherwise, different
Containers could interfere with each other and could even break applications depending on the
system time accuracy.
Normally only the server system administrator can change the system time. However, if you
want to synchronize the time via Network Time Protocol (NTP), you have to run NTP software,
which will connect to external NTP servers and update the system time. It is not advisable to run
application software on the server itself, since flaws in the software can lead to compromising
all Containers on this server. Thus, if you plan to use NTP, you should create a special
Container for it and configure it to have the sys_time capability. The example below
illustrates configuring such a Container:
# pctl set 101 --capability sys_time:on --save
Unable to set capability on running Container
Saved parameters for Container 101
The output of the above command warns you that pctl cannot apply changes in the capabilities
to a running Container. The Container has to be restarted before changes take effect:
# pctl stop 101; pctl start 101
Stopping Container ...
Container was stopped
Container is unmounted
Starting Container ...
Container is mounted
Adding IP address(es): 192.168.1.101
Hostname for Container set: Container101
Container start in progress...
# ssh root@ct101
root@ct101's password:
Last login: Mon Feb 28 23:25:58 2007 from 10.100.40.18
[root@ct101 root]# date
Mon Feb 28 23:31:57 EST 2007
[root@ct101 root]# date 10291300
Tue Feb 29 13:00:00 EST 2007
[root@ct101 root]# date
Tue Feb 29 13:00:02 EST 2007
[root@ct101 root]# logout
Connection to Container101 closed.
# date
Tue Feb 29 13:01:31 EST 2007
The command session above shows the way to change the system time from Container 101. The
changes will affect all the Containers and the server itself. It is not advisable to have more than
one Container with the sys_time capability set on.
NTP is described in Internet Standard RFC 1305; more information including client software
can be obtained from the NTP web server (http://www.ntp.org).