Linux – NTP offset warning when no NTP server is defined and NTP not running

centoslinuxntp

I just want to preface by saying that I am still learning linux and don't have too much experience with it.

My job requires me to monitor an alert system for our clients hosts that are running our product.

I just received an alert regarding NTP that confused me a bit so I was hoping someone here can help me clarify it.

The alert was for the NTP offset of a particular host. That's fine, just go and resync to the NTP server. However, turns out that there is no NTP server defined in the config file and is not even running when I go to stop it:

"ntpd: unrecognised service"

However, this check has been running for a while and only alerted today.

So my question is, if there is no NTP server defined for that host and NTP is not even running, what triggered the alert? I mean, if the alert is only supposed to go off when the offset is large, how can there be an offset if there is no server defined to be compared to?

The alert even specifies an exact time in seconds, and it's updating. So It's comparing itself to something, right?

I've tried to look online for an answer but nothing is clicking with me. Any help would be great.

Best Answer

But, before we continue, let's check the state of the ntp daemon synchronization. On that host, run:

ntpq -pn

Does this returns anything?

If it does, it looks to me that you had executed this command to stop the service:

service ntpd stop

And you've received the following message:

"ntpd: unrecognised service"

Well, in that case, you might try to stop the ntp service (no "d" on the end), like this:

service ntp stop

If that doesn't work, list what ntp* services you have on the initd dir:

ls -l /etc/init.d/ntp*

If you don't have any ntp, ntpd or ntpdate service, than you have to install it.

The service command is only valid for CentOS. For other linux flavours, replace it with /etc/init.d/ntpd stop and /etc/init.d/ntp stop.

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Linux – NTP is running, system clock still not in time – what gives

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.

Linux – NTP not updating the server time in CentOS

Your ntpd believes the remote system is stratum 16 (meaning it has the least reliable time possible). Most ntp clients will not sync with such a system. I highly recommend using pool.ntp.org as described in their directions.

Their example ntp.conf file:

driftfile /var/lib/ntp/ntp.drift

server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org

Also, you should never use IPs in the configuration file unless your system doesn't support DNS resolution by some crazy twist of requirements.

Update:
The NTP Pool project tries to make a semi-intelligent guess as to what time server it should return to you. But you should usually specify the country you want the servers to be from by using the country code in the hostnames. For India it would be:

server 0.in.pool.ntp.org
server 1.in.pool.ntp.org
server 2.in.pool.ntp.org
server 3.in.pool.ntp.org

The same drift, logging, and other options would still apply.

Best Answer

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