HostingHacks.net | Tools to Build a Linux Webhosting Service

Earth is divided in 24 time zones. The local time depends on how many zones it is away from Greenwich, Great Britain. UTC (Universal Time Coordinated) = GMT (Greenwich Mean Time). NTP is a protocol designed to synchronize the clocks of computers over a network.

last updated: Apr. 2005

Traditionally, all POSIX machines (i.e. Solaris, Linux, UNIX) have their system time in UTC format.

Set the system time to UTC:

cat > /etc/hardwareclock << "EOF"
UTC
EOF

chmod 644 /etc/sysconfig/clock

ln -sf /usr/share/zoneinfo/US/Pacific /etc/localtime

ntpdate 128.100.100.128

Set a daily synchronization with a public time servers:

cat > /etc/cron.daily/timesync.sh << "EOF"
#!/bin/sh
ntpdate 128.100.100.128 | mail -s "serv1 time sync" subzero@hosting.hacks

EOF

chmod +x /etc/cron.daily/timesync.sh
/etc/cron.daily/timesync.sh

Visit http://www.eecis.udel.edu/~mills/ntp/servers.html to find a public time server near you. With most public timeservers you should send a courtesy e-mail if you plan to use it.

US AZ ntp.drydog.com (207.211.160.111)
Location: Tempe, AZ
Synchronization: NTP V4 secondary (stratum 2) P-III/Linux 2.4
Service Area: Western United States and Northern Mexico
Access Policy: open access, please send a message to notify. Please limit access to one or two hosts per site (large sites should set up their own ntp server)
Contact: Dan Anderson ( timekeeper_at_drydog.com)
US CA ntp.ucsd.edu (132.239.254.49)
Location: UCSD Academic Computing Services/Network Operations, San Diego, CA
Synchronization: NTP secondary (stratum 2)
Service Area: CERFNET; NSFNET, SDSC region and nearby
Access Policy: open access, please send a message to notify.
Contact: timekeeper_at_ucsd.edu
US CA ntp1.mainecoon.com (63.192.96.2)
Location: Quincy, California
Geographic Coordinates: 39:56.863N, 120:54.657W
Synchronization: NTP V4 secondary (stratum 2) P-II/X86 Solaris 2.7
Service Area: North America
Access Policy: Open Access, please drop us a note so we can add you to our mailing list.
Contact:time_at_mainecoon.com or Chris Kennedy (chris_at_mainecoon.com)
Note: ntp1 is a CNAME for time service. Please use DNS; IP assignments subject to change.
US CA ntp2.mainecoon.com (63.192.96.3)
Location: Quincy, California
Geographic Coordinates: 39:56.863N, 120:54.657W
Synchronization: NTP V4 secondary (stratum 2) Sun 4/75 Solaris 2.7
Service Area: North America
Access Policy: Open Access, please drop us a note so we can add you to our mailing list.
Contact:time_at_mainecoon.com or Chris Kennedy (chris_at_mainecoon.com)
Note: ntp2 is a CNAME for time service. Please use DNS; IP
US CA ntp1.sf-bay.org (207.126.97.57)
Location: San Jose, CA
Synchronization: NTP secondary (stratum 2), FreeBSD
Service Area: North America: Northern California and Pacific Northwest
Access Policy: open access, please send a message to notify
Contact: Scott Hazen Mueller (clockmaster_at_sf-bay.org)
US CA ntp2.sf-bay.org (204.74.68.55)
Location: Los Angeles, CA
Synchronization: NTP secondary (stratum 2), FreeBSD
Service Area: North America: Southern California
Access Policy: open access, please send a message to notify
Contact: Scott Hazen Mueller (clockmaster_at_sf-bay.org)
US CA reloj.kjsl.com (204.87.183.6)
Location: Salinas, CA, USA
Synchronization: NTP V3 secondary (stratum 2), MultiNet on VMS
Service area: Western USA (Above.NET connectivity)
Access policy: open access, please drop me a note if you use the server so I can keep you on the notify list.
Contact: <timekeeper_at_kjsl.com>>
US CA time.berkeley.netdot.net (216.27.190.202)
Location: Berkeley, CA
Synchronization: NTP secondary (stratum 2), FreeBSD
Service Area: North America: Pacific Coast
Access Policy: open access, please send a message to notify
Contact: Caleb Haley (chaley_at_netdot.net)
Note: time.berkeley.netdot.net is a CNAME
US CA time.five-ten-sg.com (205.147.40.34)
Location: Lake Arrowhead, CA, USA
Synchronization: NTP V4 secondary (Stratum 2), Linux/intel
Service Area: within 100ms of Digilink.net
Access Policy: open access, email for firewall access first
Contact: carl_at_five-ten-sg.com
US CO ntp1.tummy.com
Location: tummy.com, ltd., Fort Collins, CO
Service Area: US
Synchronization: NTP Secondary (stratum 2), i686/Linux
Access Policy: open access.
Contact: ntp_at_tummy.com
Note: ntp1 is an alias and the IP address may change, please use DNS.
US NV cuckoo.nevada.edu (131.216.1.101)
Location: University of Nevada System Computing Services, Las Vegas,NV
Synchronization: NTP V3 secondary (stratum 2), DEC Alpha/Unix
Service Area: NevadaNet, NSFNET, SDSC region
Access Policy: open access, please send message to notify
Contact: Systems Group (software_at_nevada.edu)
Note: cuckoo.nevada.edu is a CNAME for alphabits.nevada.edu
US NV tick.cs.unlv.edu (131.216.22.15)
Location: UNLV College of Engineering, Las Vegas, NV
Synchronization: NTP V4 secondary (stratum 2), Solaris
Service Area: Sprintnet
Access Policy: open access, an email note is appreciated
Contact: <grayaw_at_egr.unlv.edu>
Note: select one of tick.cs.unlv.edu or tock.cs.unlv.edu at random to equalize load
US NV tock.cs.unlv.edu (131.216.22.17)
Location: UNLV College of Engineering, Las Vegas, NV
Synchronization: NTP V4 secondary (stratum 2), Mips/Unix
Service Area: Sprintnet
Access Policy: open access, an email note is appreciated
Contact: <grayaw_at_egr.unlv.edu>
Note: select one of tick.cs.unlv.edu or tock.cs.unlv.edu at random to equalize load
US NV cuckoo.nevada.edu (131.216.1.101)
Location: University of Nevada System Computing Services, Las Vegas, NV
Synchronization: NTP V3 secondary (stratum 2), Sun UltraSparc/Solaris 8
Service Area: NevadaNet, NSFNET, SDSC region
Access Policy: open access, please send message to notify
Contact: Systems Group (software_at_nevada.edu)

to set the system time (kernel) manually:

date -s "10/31/03 13:05:02"

to set the hardware clock manually:

hwclock --set --date="10/31/03 13:05:02" --utc

Changing your time-zone:

tzselect

RedHat allows the kernel to update the BIOS time at shutdown so that the BIOS will be more likely to have an accurate time when the system boots up the next time.

NTP version 3 is an internet draft standard, formalized in RFC 1305.