Monthly Archives: September 2014

Configuring and Testing NTP on ESXi

I hate NTP.  I hate time sync issues.  I hate time skew issues on ESXi.

So now that I’ve got that out I feel a whole lot better.  I can now talk about how to configure and importantly validate your NTP settings on an ESXi host.

Setting and syncing time on an ESXi host is done within Time Configuration on the Settings tab of an ESXi host.


The time can either be set manually or it can be set via NTP.  Setting the time manually is self explanatory.  Basically change your time and click OK.  It’s not something I’m going to go into any further.  Ideally, though, you want to be setting your time with NTP.  Using NTP is relatively easy too, the hardest part will be making sure you have the correct ports open on all parts of the network.  NTP generally uses UDP port 123 btw.


So firstly you want to select Use Network Time Protocol.  You next want to head over to and find your closest NTP time sources.  Understanding how the underlying technology of how NTP works is actually quite interesting but beyond what this post is about.  Wikipedia is a good start on NTP.  Each region around the world has a number of NTP pools and within those regions many countries have pools of their own.  For me my closest pool is Australia within the Oceania region.  Australia has 4 pools.  Within these pools are actually a number of servers.  I can use one of these pools or I can use them all.  I’ll be using them all for redundancy.  Once I enter these pool addresses and separate them with commas I click the Start button and click OK.


The Time Configuration should now look something similar to below.  The time change in not instant and can take… well… time.


But how do you test that these settings are correct, considering that the time sync process is not instant.  Further more, NTP uses UDP port 123 which is connectionless.  Well, we can query the output our NTP sources gives us, which can be done from the CLI of the ESXi host.

Log into the console of the ESXi host using whatever method you prefer.  The simplest is usually just starting and connecting to SSH.

We use the NTPQ command and type the following.

ntpq -p localhost

The output should be sometime similar to below.  VMware have a good KB article which explains what it all means if your really want to know.


If we see something similar we know we’re good and the time should start to change shortly.  If we get all zeros we probably have network and DNS working but NTP is block at the firewall somewhere.


Part 4: The NUC for Weight Weenies

As a cyclist and a self professed weight weenie, if the NUC was a bicycle component it would surely have to be on the wish list of many riders.

My second Intel NUC arrived in the post recently.  For this second NUC I went with the i5 D54250WYK model.  Again I maxed out its memory and went with 16 GB and for the SSD I upped it from the previous 120 GB to the 240 GB Crucial.  Now knowing that I can install a working ESXi image on a NUC.  I felt comfortable purchasing the faster i5 model and increased SSD storage capacity for a home lab.

With the memory and mSATA SSD installed I decided to weight the NUC on my bike kitchen scales.  Clocking in at 504 grams is pretty impressive I think.  Weighing less than a 600 ml bottle of coke.  It’s light enough to stick in your bag and take to work.  One of the marketing angles of the NUC is a media center.  Being able to put a 4K capable media center in your bag and to a friend joint is pretty cool.



Articles in this series

Part 1: The NUC Arrival
Part 2: ESXi Owning The NUC
Part 3: Powering a NUC Off A Hampster Wheel
Part 4: The NUC for Weight Weenies
Part 5: Yes, you can have 32GB in your NUC