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323

This is caused by a livelock when ntpd calls adjtimex(2) to tell the kernel to insert a leap second. See lkml posting http://lkml.indiana.edu/hypermail/linux/kernel/1203.1/04598.html Red Hat should also be updating their KB article as well. https://access.redhat.com/knowledge/articles/15145 UPDATE: Red Hat has a second KB article just for this issue here: ...


33

This hit us hard. After restarting many of our hosts, the following turned out to be embarrassingly simple and fully effective without a host restart: /etc/init.d/ntp stop ntpdate 0.us.pool.ntp.org /etc/init.d/ntp start All that is required is to reset the system clock. Sheesh. What I've give to have known this six hours ago.


30

http://www.pool.ntp.org/ If you are in the US: United States — us.pool.ntp.org To use this pool zone, add the following to your ntp.conf file: server 0.us.pool.ntp.org server 1.us.pool.ntp.org server 2.us.pool.ntp.org server 3.us.pool.ntp.org Other pools around the world are available and can be found at the http://www.pool.ntp.org/ site.


24

The NTP algorithm includes information to allow you to calculate and fix the drift in your server's clock. NTPD includes the ability to use this to keep your clock in sync and will run more accurately than a clock on a computer not running NTPD. NTPD will also use several servers to improve accuracy. ntpdate does not keep any state to perform this service ...


24

A simple C program that clears the leap second bit in the kernel's time status field: #include <sys/timex.h> #include <string.h> #include <stdio.h> int main(int argc, char **argv) { struct timex txc; int ret; (void) argc; (void) argv; bzero(&txc, sizeof(txc)); txc.modes = 0; /* fetch */ ret = adjtimex(&...


23

In the old days, setting up a stratum-1 NTP server was very difficult, because stratum-0 sources were very expensive, extremely delicate, and usually radioactive. Nowadays we have the GPS, which incidentally functions as an extremely accurate radio clock. You can buy a dedicated stratum-1 server containing a GPS receiver as its stratum-0 timesource for ...


21

The Network Time Protocol, or NTP, can be used to synchronize the time on a server with an authoritative source. Windows Servers, for example, will use one of the network domain controllers (the DC which holds the PDC emulator FSMO role for the domain [thanks Graeme]) to get time information. You can configure the domain controller to get information from ...


21

Databases don't like backward steps in time, so you don't want to start with the default behavior of jumping the time. Adding the -x option to the command line will slew the time if the offset is less than 600 seconds (10 minutes). At maximum slew rate it will take about a day and half to adjust the clock by a minute. This is a slow but safe way to adjust ...


20

This is easy to control. Configuration management is the key... Ensure that the ntp service is running and configured... For example, using Monit to make sure ntpd is running and to restart it if it fails is an easy approach... It may make sense to add cron and other essential daemons to that sort of check. Another option is using a configuration ...


19

I would log everything in UTC (Coordinated Universal Time), this way daylight saving is never observed. It is the common default time setting for Linux servers. You can then present both the UTC and the local timezone time at the application layer. Reading about the tzdata package might be of interest to you. From that Wikipedia article: UTC does ...


19

You have the list of registry values here. Referring to this, try setting the following values : SpecialPollInterval : HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient Explanation : Version : Windows XP, Windows Vista, Windows Server 2003, and Windows Server 2008 This entry specifies the special poll ...


19

As with most things, "it depends". Are all of your administrators/users in the same timezone? Perhaps their TZ would be appropriate. Do the machines interact with the local environment? Local TZ might be good. Are all the logs pulled to a central location for analysis? UTC might help there. Do the machines communicate with each other in ways where time ...


18

Set everything to UTC. In addition to the examples user48838 mentioned, most things related to aviation are given in Zulu time (same as UTC/GMT). e.g. flight plans are filed with takeoff and landing times in UTC.


18

Postmortem it seems ./lsec does not have an effect. What we're seeing is lots of softirqd processes eating CPU (usually linear to the load of java processes) What does work to fix POSTMORTEM with leap seconds already applied by ntp is the following: It appears to be sufficient to just issue: export LANG="en_EN"; date -s "`date`" This should reduce the ...


17

Jeff, I found this article. Might be of some help to you. You might have already read this but I thought it was worth a shot. HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Config\AnnounceFlags This registry entry controls whether the local computer is marked as a reliable time server (which is only possible if the previous registry entry is set ...


17

The simple fact is that clock accuracy within a VM is still really bad. This comes from a few spots, but the killer thing is that the time drift is not constant; the drift factor changes from moment to moment. NTP is a protocol that has clock compensation built within it, but it was designed with a static drift factor built in. For example, if a physical ...


17

You only need to set the time zone once: tzselect or dpkg-reconfigure tzdata NTP does not handle time zones. All time data handled by NTP is in UTC; your local time zone setting determines the offset from there.


17

http://my.opera.com/marcomarongiu/blog/2012/03/12/no-step-back seems to indicate that the Debian squeeze kernel won't handle the leap second. This thread on comp.protocols.tim.ntp is of interest, also: https://groups.google.com/forum/?fromgroups#!topic/comp.protocols.time.ntp/KSflIgjUdPE That said, the leap second hasn't happened yet: 23:59:60 UTC Finally,...


17

Essentially, you're outta luck if the DDoS attack manages to fill whatever pipe you have to the Internet (which is the purpose of any UDP reflection attack -- to fill the pipe). If your upstream link can take 1Gbps of traffic, and there's (say) 2Gbps of traffic total to go down the link, then half of it is going to be dropped by the router or switch that's ...


16

The pool.ntp.org is a DNS-level load balancer. Jeff just happened to get directed to that one, the NTP pool maintainers do not care what does the server run on it's port 80 (http), only that it serves time via NTP correctly.


16

ntpd doesn't sync time periodically the way you think it does, see here for more information (read the whole thing, it's all important. Short version: ntpd syncs the time and tells the system how fast it's drifting away from "true" time, the system then adjusts its clock frequency to properly track "true" time. Within a day most systems are tracking to ...


15

Stop ntpd, run ntpdate -u 0.europe.pool.ntp.org 3 times, start ntpd, check up on ntpq -p, delay, offset and jitter should be non-zero.


15

It is not promiscuous at all. It's just binding to the interface IP addresses and localhost, both on ipv4 and ipv6 protocols. If you think it should not be listening to some of those, just change the listen config as explained in the manual (this may be for a different version that you are using): listen on address Specify a local IP address or a ...


15

These attacks have been around for ages, they just became popular again the last couple of months. They work like any regular amplification attack: a host spoofs a query so that the source IP address seems to be the targetted host. The NTP server sends its answer to the spoofed address. Since the answer for specific query types can be quite large and usually ...


15

Here is my recommended configuration for Windows Domain Time Synchronization, pieced together from several Microsoft TechNet articles and blog posts. If your servers are virtualized, do not use any of the VMware tools time sync features. Just let the Windows Time Service (w32time) do its job. VMware even says so. I assume the same is true for Hyper-V. ...


15

Connecting your ntpd to NTP servers outside your LAN to time sync can lead to the inconsistencies you are seeing, because every connection will have to go thru several routers, each one with unpredictable latencies depending on traffic. If each server connects by itself, the time between all the servers will drift a little. To avoid the inconsistency, the ...


15

I see some confusion going on in the answers here. For starters, ntpclient, at least in -s mode, isn't acting as a full NTP client, it's only sending and receiving one packet, so there's no "last 8 packets received". It isn't actually estimating its own dispersion at all. Instead, the value it's printing is the value called "root dispersion" (rootdisp) in ...


14

Windows Time Agent is a free control panel applet for configuring the NTP server/synchronization ability of Windows. It acts as a front-end to the registry settings and lets you configure multiple NTP servers and see what sort of results you are getting from them in real-time. Not many people know about this particularly handy (and free) piece of software, ...


14

ntpq -p ntp.ubuntu.com From man ntpq: ... -p Print a list of the peers known to the server as well as a summary of their state. This is equivalent to the peers interactive command. ... Edit: The host is timing out right now. ntpq -p pool.ntp.org will return a valid result.


14

In a perfect world, your VM guests would keep perfect time, or at least as perfect as the host provides. Unfortunately we don't live in a perfect world. Based on my experience with virtually every hypervisor known to man, I always run an NTP client in virtual machines, without exception. My usual setup is ntpd with the -g option, or ntpdate starting right ...



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