Modelo de cuaderno de a bordo u hoja de ruta

The clock synchronization is mandatory for system working together with Kerberos authentica- tion tool, to do it the Network Timing Protocol (NTP) specified by RFC 1305 has to be configured by fol- lowing the instructions shown in this paragraph.

If NTP is not configured you have to check the time difference among all the systems and guarantee that it doesn't exceed five minutes.

Before proceeding with the NTP configuration you must have a clear picture of the configuration among the involved machines, it is advisable to prepare a "time distribution plan" taking into account the following rules:

a) The primary time sources have to be reliable ones, such as a Global Position System (GPS) receiver time source.

b) Define two or three time-server machines. Each time-server should be a peer with of the other time- servers.

c) If possible, do not synchronize multiple time-servers to the same outside source.

d) If you choose to use an HPTM _{server as time source, it must be configured to be synchronized with}

its internal clock.

For example in a network with two GPS receivers and five nodes, with the following roles: – host and hosted configured with: EML and SDH co-hosted with HA.

– hostly, host and hostel preform the presentation function for the resilient servers.

The resilient hosts plus a presentation (host) can be configured to receive the time from the GPS receives, and swap the time among themselves. All the other servers in the network (hostly and hostel) have to be configured to receive the time from the host, host e hosted.

GPS

GPS Receiver 1 GPS Receiver 2

hosta

hostb hostd hoste

hostc WAN WAN IP 192.200.49.1 IP 192.202.21.7 IP 192.202.21.8 IP 192.202.22.4 IP 192.202.22.5 IP 192.202.22.20 IP 192.202.21.51

To obtain such a configuration the three time servers you have to declare the two Receivers as NTP serv- ers, moreover they can declare the other ones as peers; the resulting configuration will be:

hosta

server gpsrec1 prefer server gpsrec2 peer hostc peer hostd hostc

server gpsrec1 prefer server gpsrec2 peer hosta peer hostd hostd

server gpsrec1 server gpsrec2 prefer peer hosta

peer hostc

The “prefer" attribute distinguishes as the preferred source, this source it is usually the most reliable and also the nearest one.

The remaining servers can retrieve the time from the other ones, here after the configuration: hosta

server hostb prefer server hostc server hostd hoste

server hostb server hostc server hostd prefer

To make easier the NTP configuration the “scxntp" script is provided.

To start “scxntp" script, login the system as root user and enter: scxntp [Enter]

======================================================================== OS-Conf xntp Protocol Configuration

======================================================================== 1 - Add new NTP server

2 - Add new NTP peer 3 - Remove NTP server 4 - Remove NTP peer

5 - Configure NTP on local clock 6 - Show NTP configuration

7 - Show NTP status

8 - Start/Stop NTP server 9 - Align the time to server e or q - for exit

to simplify the explanation, the procedure shows how to configure the server hostb and hosta of Figure 9.at page 84. Note, the configuration order is relevant for the system behavior, it is better to start config- uring the nodes more close to the Timeservers.

2.3.2.1 Configure hostb

This is the procedure using scxntp script to configure the hostb of Figure 9.at page 84. a) Login hostb as root user.

b) Start the scxntp script by entering: scxntp [Enter] c) Define the preferred timeserver:

Insert choice and press [Enter]: 1

Enter server hostname or IP address or q for Quit : 192.202.21.51 NOTE: Checking the configuration ...

Would you like to set 192.202.21.51 as preferred (y/n) ? y NOTE: Updating /etc/ntp.conf adding server 192.202.21.51 ...

NOTE: Setting 192.202.21.51 timeserver for synchronize at boot time Press return to continue ...

d) Define the secondary timeserver:

Insert choice and press [Enter]: 1

Enter server hostname or IP address or q for Quit : 192.202.22.20 NOTE: Checking the configuration ...

Would you like to set 192.202.22.20 as preferred (y/n) ? n NOTE: Updating /etc/ntp.conf adding server 192.202.22.20 ... Press return to continue ...

e) For each peer hosts enter:

Enter server hostname or IP address or q for Quit : 192.202.21.8 NOTE: Checking the configuration ...

Would you like to set 192.202.21.8 as preferred (y/n) ? n NOTE: Updating /etc/ntp.conf adding peer 192.202.21.8 ... Press return to continue ...

f) Start the NTP Daemon, set-up the daemon automatic start at system startup, and synchronize the hostb clock with the preferred server in one shot:

Insert choice and press [Enter]: 8

WARNING: The xntpd daemons it is not configure to start automat... Would you like to start xntpd automatically at reboot (y/n) ? y NTP server is stop

Would you like to start it (y/n) ?y

NOTE: Temporary setup xntpd autostart... NOTE: Starting xntpd ...

4 Sep 18:33:01 ntpdate[14482]: step time server 151.98.45.29 offset -0.026898 sec

xntpd NOTE: Reset the setup xntpd autostart... Press return to continue ...

2.3.2.2 Configure host

This is the procedure using scxntp script to configure the hosta of Figure 9.at page 84. a) Login hosta as root user.

b) Start the scxntp script by entering: scxntp [Enter] c) Define the preferred timeserver:

Insert choice and press [Enter]: 1

Enter server hostname or IP address or q for Quit : 192.202.21.7 NOTE: Checking the configuration ...

Would you like to set 192.202.21.51 as preferred (y/n) ? y NOTE: Updating /etc/ntp.conf adding server 192.202.21.51 ... NOTE: Setting 192.202.21.51 timeserver for synchronize at boot time Press return to continue ...

d) Define the other two timeserver:

Insert choice and press [Enter]: 1

Enter server hostname or IP address or q for Quit : 192.202.21.8 NOTE: Checking the configuration ...

Would you like to set 192.202.22.20 as preferred (y/n) ? n NOTE: Updating /etc/ntp.conf adding server 192.202.22.20 ... Press return to continue ...

e) Start the NTP Daemon, set-up the daemon automatic start at system startup, and synchronize the hosta clock with the preferred server in one shot:

Insert choice and press [Enter]: 8

WARNING: The xntpd daemons it is not configure to start automatically Would you like to start xntpd automatically at reboot (y/n) ? y NTP server is stop

Would you like to start it (y/n) ?y

NOTE: Temporary setup xntpd autostart... NOTE: Starting xntpd ...

4 Sep 18:33:01 ntpdate[14482]: step time server 151.98.45.29 offset -0.026898 sec

xntpd NOTE: Reset the setup xntpd autostart... Press return to continue ...

f) Leave script by entering “e" or “q".

The script allows to easily manage the NTP configuration, you can add or/and delete servers and/or peers, show the configuration, stop and start the NTP daemon, or align in one shot your system time to a specific server.

Defining a NTP server the management script allows to specify the preferred one, it is not recommended to define more than one preferred server.

The NTP mechanism takes a long time to synchronize the machine with server. The NTP dae- mon has to be stopped and started each time the configuration changes. Usually the NTP daemon is not running.

2.3.2.3 Initial Clock Alignment

When a machine is installed for the first time, the clock is not synchronized with any reference, the easiest way to synchronize it with the other is by running “scxntp" script selecting the option N.9 “Align the time to server".

N.B. The time alignment is forbidden when NTP daemon is running.

To align the time you have to login the system as root user and start the script “scxntp" by entering:

...,sys,root# scxntp[Enter]

======================================================================== OS-Conf xntp Protocol Configuration

======================================================================== 1 - Add new NTP server

2 - Add new NTP peer 3 - Remove NTP server 4 - Remove NTP peer

5 - Configure NTP on local clock 6 - Show NTP configuration

7 - Show NTP status

8 - Start/Stop NTP server 9 - Align the time to server e or q - for exit

Insert choice and press [Enter]: At the prompt enter “9 [Enter]"

Enter server hostname or IP address or q for Quit :

The procedure will ask you to enter the IP address or Hostname of the timeserver, enter it and press [Enter] key. The time will be aligned and shown.