Network Time Protocol daemon (简体中文)
OpenNTPD is a FREE, easy to use implementation of the Network Time Protocol. 能够使本地时间和NTP服务器的时间同步，同时也能使本地时间变成一个NTP服务器，发布给其他用户。
OpenNTPD is primarily developed by Henning Brauer as part of the OpenBSD Project.
OpenNTPD is a brand new implementation of the ntp protocol. 相对于NTPD，OpenNTPD比较容易配置和使用。
首先,安装 OpenNTPD package ——这包Arch Linux社区已经提供了（in the Arch Linux community repository）。
pacman -S openntpd
# $OpenBSD: ntpd.conf,v 1.7 2004/07/20 17:38:35 henning Exp $ # sample ntpd configuration file, see ntpd.conf(5) # Addresses to listen on (ntpd does not listen by default) #listen on * #listen on 127.0.0.1 #listen on ::1 # sync to a single server #server ntp.example.org # use a random selection of 8 public stratum 2 servers # see http://twiki.ntp.org/bin/view/Servers/NTPPoolServers servers pool.ntp.org
The "servers" directive works the same as the "server" directive, however, if the dns name resolves to multiple IP address, ALL of them will be synced to. 其实，默认的 "pool.ntp.org"已经可以满足大部分要求了。具体的时间服务器可以到这查看：www.pool.ntp.org/zone/asia
Any number of "server" or "servers" directives may be used.
If you want the computer you run OpenNTPD on to also be a time server, simply uncomment and edit the "listen" directive.
listen on *
will listen on all interfaces.
listen on 127.0.0.1
will only listen on the loopback interface.
If you would like to run OpenNTPD at boot, add openntpd the DAEMONS variable in your /etc/rc.conf.
net time set /bin/date
pacman -S ntp
The very first line of your ntp.conf file should contain a line such as the following:
restrict default noquery notrust nomodify
This essentially restricts everyone from modifying anything. Following this, you need to let ntpd know what you want to let through into your NTP server. Here is where you would specify any other ip addresses you would like to synchronize on your NTP server. For example:
restrict 126.96.36.199 restrict 192.168.0.0 mask 255.255.255.0 nomodify
This tells ntpd that 188.8.131.52 and all ip addresses from the 192.168.0.0 range will be allowed to synchronize on this server, but they will not be allowed to modify anything. All other IP addresses in the world will still obey the default restrictions (the first line in the ntp.conf).
Now, is where the stratum 2 servers that our server will synchronize with come into play. The lines in ntp.conf will be used to tell ntpd what servers we would like to use for synchronizing (these are just examples; use ntp servers that are closest to your location). Please see http://ntp.isc.org/bin/view/Servers/NTPPoolServers for a list a closer servers.
server ntp1.cs.wisc.edu server ntp3.cs.wisc.edu server ntp3.sf-bay.org
Unless you have a good reason not to, it is advisable to use the pool.ntp.org servers: http://www.pool.ntp.org/. Alternatively, a list of ntp servers is available at http://www.eecis.udel.edu/~mills/ntp/clock2a.html. Please pay attention to the Access Policies.
If we left it alone right now, we would never connect to a server because the response from any of the three servers listed above would never be allowed back into our server due to the fact that our default restrict statement would be in use (since we did not add the servers to our lesser restrictions (like we did with 127.0.0.1 and the subnet of 192.168.0.0).
To correct this, enter the following lines in ntp.conf:
restrict ntp1.cs.wisc.edu noquery nomodify restrict ntp3.cs.wisc.edu noquery nomodify restrict ntp3.sf-bay.org noquery nomodify
This will allow the response from the above servers into our system so our local clock can be synchronized. The noquery restriction will not allow any of the above three servers to query for information from our server. The nomodify restriction will not allow the three servers to modify anything (synchronization will still take place).
The only thing left to do is add the drift file (which keeps track of yours clocks time deviation). and the log file location:
driftfile /etc/ntp.drift logfile /var/log/ntp.log
The complete file will look like this:
# default restrictions restrict default noquery notrust nomodify # override the default restrictions here restrict 10.1.1.0 mask 255.255.255.0 nomodify # public NTP servers to sync with (all stratum 2) server ntp1.cs.wisc.edu server ntp3.cs.wisc.edu server ntp3.sf-bay.org restrict ntp1.cs.wisc.edu noquery nomodify restrict ntp3.cs.wisc.edu noquery nomodify restrict ntp3.sf-bay.org noquery nomodify # NTP drift file - used to keep track of your system clocks # time deviation driftfile /etc/ntp.drift # NTP log file logfile /var/log/ntp.log
Take note that this is for a client and a server ntp.conf configuration. If you just want to synchronize with a stratum server and are not concerned with other PCs synchronizing with your ntp server, then you can do something like the following (note that only 127.0.0.1 is allowed to be synchronized):
# default restrictions restrict default noquery notrust nomodify # Permit all access over the loopback interface restrict 127.0.0.1 # public NTP servers to sync with (all stratum 2) server ntp1.cs.wisc.edu server ntp3.cs.wisc.edu server ntp3.sf-bay.org restrict ntp1.cs.wisc.edu noquery nomodify restrict ntp3.cs.wisc.edu noquery nomodify restrict ntp3.sf-bay.org noquery nomodify # NTP drift file - used to keep track of your system clocks # time deviation driftfile /etc/ntp.drift # NTP log file logfile /var/log/ntp.log
... or if you don't care about restrictions at all, something like this (note there are no restrictions, thus no need to reduce restrictions for 127.0.0.1 to allow your local clock to synchronize):
# public NTP servers to sync with (all stratum 2) server ntp1.cs.wisc.edu server ntp3.cs.wisc.edu server ntp3.sf-bay.org # NTP drift file - used to keep track of your system clocks # time deviation driftfile /etc/ntp.drift # NTP log file logfile /var/log/ntp.log
A Note about Security
You may wonder about all of the restrict lines. The reason for them is security. If you don't want a secure NTP server, don't add any restrict lines to your ntp.conf file. If you want a secure NTP server, start out by adding a default restrict that doesn't allow anything to contact your server, then add more (less restrictive) restrict lines - allowing certain addresses various access privileges.
/etc/rc.d/network file modification
One more thing that you may want to do. 大多数情况下， /etc/ntp.conf 会被dhcp重写，为防止发生这情况，编辑 the /etc/conf.d/dhcpcd ， add -N to the line that starts with 'dhcpcd -t 10'.
FYI: This was my experience/solution with setting the time.
On my system my /etc/conf.d/dhcpcd contains a single line:
DHCPCD_ARGS="-t 30 -h $HOSTNAME"
I assume it needs to be changed to:
DHCPCD_ARGS="-N -t 30 -h $HOSTNAME"
Some have suggested adding -R to preserve /etc/resolv.conf as well.
To fix Time use /etc/rc.local
To set the correct time; Set time and start ntpd at boot via /etc/rc.local
Relevant sections of /etc/rc.conf
HARDWARECLOCK="UTC" TIMEZONE="US/Mountain" Network/ DHCP section: lo="lo 127.0.0.1" eth0="dhcp" INTERFACES=(lo eth0) Daemons subsection: DAEMONS=(syslog-ng hotplug !pcmcia network netfs !ntpd crond dbus hal alsa gdm)
This is my /etc/rc.local
#!/bin/bash # # /etc/rc.local: Local multi-user startup script. # # Re-copy ntp.conf (was over written by dhcp) cp /root/CONFIG.BAK/ntp.conf.bac /etc/ntp.conf # I advise you keep your desired /etc/ntp.conf # OUTSIDE of /etc # Set time /usr/bin/ntpdate ntp.nasa.gov #Use any time server you like here # Start ntpd /etc/rc.d/ntpd start
And here is my /root/CONFIG.BAK/ntp.conf.bac (this is just a copy of the desired /etc/ntp.conf)
# default restrictions restrict default noquery notrust nomodify # override the default restrictions here restrict 127.0.0.1 nomodify restrict 192.168.2.0 mask 255.255.255.0 nomodify # public NTP servers to sync with (all stratum 2) server ntp.nasa.gov #Use any time server you like here restrict ntp.nasa.gov noquery nomodify # NTP drift file - used to keep track of your system clocks driftfile /etc/ntp.drift # NTP log file logfile /var/log/ntp.log
Leave /etc/conf.d/dhcpcd at default. Mine is a single line and reads
DHCPCD_ARGS="-t 30 -h $HOSTNAME"
With this configuration I get the correct time and ntpd running at boot. There may be a better way, but this worked for me. I hope it helps.
Updating your system immediately using ntpdate
建议在/etc/rc.local加上下面一行，这样在系统启动时，就能和NTP时间同步 (服务器地址用一个对你来说快点的 NTP 服务器).
Running ntpdate when you boot up is a good idea because ntpd may take a long time to synchronize your local clock depending on how far off the time is. If your clock is synchronized when ntpd starts, then it's sole purpose is to keep it synchronized. To run ntpd at startup, add ntpd to the daemons section of the /etc/rc.conf file.
ntpd will work well if you have a connection to the internet all the time. If you are using dialup, you may just want to stick with using ntpdate via the command line.
Querying your NTP server using ntpq
There is a default restrict statement for the localhost that includes an ignore flag. Without overriding it (adding the line restrict 127.0.0.1) you will not be able to query your NTP server. If that's not a concern to you, then leave out the restrict line for your localhost. You will still be able to synchronize with your stratum 2 servers.