linux app for syncing hardware clock?

unclejed613 · 08-08-2010, 12:57 PM

i need to be able to sync my linux box to something like www.worldtimeserver.com

how? there don't seem to be any 3rd-party apps for it, so is it already in linux?

dugan · 08-08-2010, 01:04 PM

ntpdate

It's part of a default Slackware installation.

unclejed613 · 08-08-2010, 02:23 PM

tnx.....

i see there's no man page for it, what are the options?

Richard Cranium · 08-08-2010, 02:31 PM

Look in /usr/doc/ntp-4.2.6p1/html/ntpdate.html

michaelk · 08-08-2010, 02:46 PM

Yes, the daemon used for syncing computers clocks is called ntp. I suggest running ntp over ntpdate because ntp will adjust for clocks errors whereas ntpdate just sets the time.

http://en.wikipedia.org/wiki/Network_Time_Protocol
http://linux.die.net/man/1/ntpdate

As stated it should be part of the default Slackware installation. What version of slack are you running?
Does /etc/ntp.conf or /etc/rc.d/rc.ntpd exist?

unclejed613 · 08-08-2010, 09:27 PM

tnx, the file:/// link didn't work.... the link to the linux web page did.... so how would i go about setting up cron to automatically update my clock once every 24hrs or so? i've been using linux "part-time" for about 10 years, and "full-time" for only about a year, so there's a lot i still need to learn...

edit: so i created a script called "update-time" with this as the execution line:
/usr/sbin/ntpdate www.worldtime.com

i then placed this file in /etc/cron.daily/

so i gather that this script will execute daily? without using crontab? my pc's clock loses about 1/10 minute per day, and it adds up after a while.

Richard Cranium · 08-08-2010, 10:15 PM

Quote:

Originally Posted by unclejed613

tnx, the file:/// link didn't work.... the link to the linux web page did.... so how would i go about setting up cron to automatically update my clock once every 24hrs or so? i've been using linux "part-time" for about 10 years, and "full-time" for only about a year, so there's a lot i still need to learn...

Hmm, that's right; the file:/// link doesn't work. Odd. Oh well, it should point into your installed ntpd documentation. Just remove the leading file:// part.

If you have a permanent connection to the web, then you should just run ntpd and forget about it. See this thread, which actually gives a good set of example configuration files.

But just make an executable script containing...

Code:

#!/bin/sh
/usr/sbin/ntpd -q -x -g

...and drop it into /etc/cron.daily/ to set the clock once a day if that's what you'd really prefer.

Richard Cranium · 08-08-2010, 10:17 PM

Quote:

Originally Posted by unclejed613

edit: so i created a script called "update-time" with this as the execution line:
/usr/sbin/ntpdate www.worldtime.com

i then placed this file in /etc/cron.daily/

so i gather that this script will execute daily? without using crontab? my pc's clock loses about 1/10 minute per day, and it adds up after a while.

Well, it uses root's crontab to run that. Root has a crontab entry of...

Code:

# Run daily cron jobs at 4:40 every day:
40 4 * * * /usr/bin/run-parts /etc/cron.daily 1> /dev/null

Bear in mind that ntpdate will eventually go away.

Eternal_Newbie · 08-09-2010, 08:47 AM

that's not really the best way to do it. Read http://www.pool.ntp.org/en/ and http://en.wikipedia.org/wiki/NTP_ser...suse_and_abuse for why it is not recomended doing it that way.

Also, www.worldtime.com doesnt appear to accept ntp connections, which you are attempting to do:

Code:

root@foobar:/etc/rc.d# /usr/sbin/ntpdate worldtime.com
 9 Aug 15:37:47 ntpdate[7537]: no server suitable for synchronization found
root@foobar:/etc/rc.d# /usr/sbin/ntpdate www.worldtime.com
 9 Aug 15:38:10 ntpdate[7548]: no server suitable for synchronization found
root@foobar:/etc/rc.d# /usr/sbin/ntpdate ntp.worldtime.com
Error : Name or service not known
 9 Aug 15:40:49 ntpdate[7618]: can't find host ntp.worldtime.com

 9 Aug 15:40:49 ntpdate[7618]: no servers can be used, exiting

If you are using Slackware set up your pool servers in /etc/ntpd.conf and make /etc/rc.d/rc.ntpd executable and then run

Code:

/etc/rc.d/rc.ntpd start

(or restart) as root.

This is my /etc/ntpd.conf, which is just the default slackware one with pool servers added:

Code:

# Sample /etc/ntp.conf:  Configuration file for ntpd.
#
# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available. The
# default stratum is usually 3, but in this case we elect to use stratum
# 0. Since the server line does not have the prefer keyword, this driver
# is never used for synchronization, unless no other other
# synchronization source is available. In case the local host is
# controlled by some external source, such as an external oscillator or
# another protocol, the prefer keyword would cause the local host to
# disregard all other synchronization sources, unless the kernel
# modifications are in use and declare an unsynchronized condition.
#
#server  127.127.1.0     # local clock
#fudge   127.127.1.0 stratum 10  
server  0.uk.pool.ntp.org
server  1.uk.pool.ntp.org
server  2.uk.pool.ntp.org
server  3.europe.pool.ntp.org

#
# Drift file.  Put this in a directory which the daemon can write to.
# No symbolic links allowed, either, since the daemon updates the file
# by creating a temporary in the same directory and then rename()'ing
# it to the file.
#
driftfile /etc/ntp/drift
multicastclient                 # listen on default 224.0.1.1
broadcastdelay  0.008

#
# Keys file.  If you want to diddle your server at run time, make a
# keys file (mode 600 for sure) and define the key number to be
# used for making requests.
# PLEASE DO NOT USE THE DEFAULT VALUES HERE. Pick your own, or remote
# systems might be able to reset your clock at will.
#
#keys           /etc/ntp/keys
#trustedkey     65535
#requestkey     65535
#controlkey     65535

# Don't serve time or stats to anyone else by default (more secure)
restrict default noquery nomodify
# Trust ourselves.  :-)
restrict 127.0.0.1

Note I am using UK pool servers. You will want to use pool servers close to you, if possible. Check http://www.pool.ntp.org/en/use.html for details how to do this. If your country has only a couple of pool servers it is better to use the region instead of the country so you don't overtax them. Some regions like Africa have only a few servers as well, so if you are from one of those regions it may be better to specify only 1 or 2 of your servers as a regional one and use worldwide pool servers.

Richard Cranium · 08-09-2010, 09:04 AM

Quote:

Originally Posted by Eternal_Newbie

thats not relly how you should do it. Read http://www.pool.ntp.org/en/ and http://en.wikipedia.org/wiki/NTP_ser...suse_and_abuse for why it is a bad idea doing it that way.

Those links state nothing of the sort that I could see.

Even so, I agree that simply setting up ntpd to run correctly is the better approach; that's what I do.

Eternal_Newbie · 08-09-2010, 09:58 AM

Quote:

Originally Posted by Richard Cranium

Those links state nothing of the sort that I could see.

Even so, I agree that simply setting up ntpd to run correctly is the better approach; that's what I do.

Sorry I didn't see your reply when I edited my previous post, I'll post what I noticed here as well:

Quote:

Originally Posted by unclejed613

so i created a script called "update-time" with this as the execution line:
/usr/sbin/ntpdate www.worldtime.com

i then placed this file in /etc/cron.daily/

You appear to want to use ntpdate with www.worldtime.com and they don't appear to accept ntp connections:

Code:

root@foobar:/etc/rc.d# /usr/sbin/ntpdate worldtime.com
 9 Aug 15:37:47 ntpdate[7537]: no server suitable for synchronization found
root@foobar:/etc/rc.d# /usr/sbin/ntpdate www.worldtime.com
 9 Aug 15:38:10 ntpdate[7548]: no server suitable for synchronization found
root@foobar:/etc/rc.d# /usr/sbin/ntpdate ntp.worldtime.com
Error : Name or service not known
 9 Aug 15:40:49 ntpdate[7618]: can't find host ntp.worldtime.com

 9 Aug 15:40:49 ntpdate[7618]: no servers can be used, exiting

You need you use a valid ntp server for which you often need permission to access, which is why using the pool servers with ntpd is best.

unclejed613 · 08-09-2010, 10:01 PM

i'm using the computer for weak signal decoding, which should use at least a stratum 2 server. JT65 signals only need the computer clock to be within a few seconds, but propagation beacons require somewhat better timing, less than a second IIRC.

you're right about www.worldtime.com, it didn't work. i put in www.worldtimeservers.com and that works, as does wwv.nist.gov (that's not a typo, that's WWV, the NIST's standard time and frequency station, which is local to me.

as far as the misuse and abuse part of it goes, i connect once daily at 1am (not midnight, when i imagine a majority of scripts are running), and the address isn't "hard coded" in firmware, and ntpdate doesn't hammer the connection until it gets a reply. i'm not also producing millions of identical devices and flooding the market with them. on an interesting side note, LG blu-ray players and set-top boxes ping www.whitehouse.gov to determine whether they are still connected to the internet at regular intervals. i don't know what the govt did to piss off LG (maybe the goofy stuff that went on with the DTV switchover, such as forcing companies to mass produce DTV/analog STB's, selling them dirt cheap, and taking a huge hit in their R&D budgets?), but every LG product that is internet capable (blu-ray players, DTV STB's, TV's, etc) is periodically pinging www.whitehouse.gov, just to see if it's still conected...

edit: also, i found KDE's crontab editor to be extremely useful, i didn't even need a handful of hastily scribbled notes to get the process set up...