9th June 2018

Technical Resources

A collection of my Technical Resource documentation.

Latest Tech Articles

7th September 2020

Using Chrome DevTools to view Your website in “Mobile View”

Follow the below to view Your website as it would be displayed on a Mobile Device using Google Chrome’s DevTools.

Firstly, open Google Chome Website Browser (Click the text if You do not have Google Chrome installed to install the browser).

Browse to Your website in Google Chrome

Press the F12 button on Your keyboard to open up Chrome DevTools (Eg below)

Now click the button at the top to force Chrome to preview Your website in Mobile View:

After clicking this, Your mobile will be displayed with a default “Responsive” Mobile view. If You wish to see how Your website will be displayed for a particular device, You can click on the “Responsive” link at the top to select a particluar Mobile Device (which will adjust the resolution in the displayed view).

To revert back to the usual Desktop view, simply close DevTools by clicking on the X at the top right of the DevTools Window.

30th March 2020

Forcing Windows Servers to sync NTP Time more frequently

By default, Windows will only sync it’s NTP time every 17 minutes. To update the server to sync time more often this can be set via Group Policy (Either locally if the machine is not joined to a domain or centrally if in a Domain controlled environment).

Group Policy setting:

Instructions will be the same for Domain Controlled and local Group Policy (gpedit.exe):

  • Open up Group Policy settings
  • Go to:Local Computer Policy > Computer Configuration > Administrative Templates > System > Windows Time Service
  • Double click on Global Configuration Settings
    • Select “enabled” at the top of the Window
    • Scroll down to MinPollInterval and MaxPollInterval and set these as appropriate (minimum is 2 min /3 max ). NOTE: These times are in base-2

Apply the Group Policy change

Run the below to update Group Policy on the server:

gpupdate /force

Confirm current time sync status / sync time:

To confirm that the setting has applied, run the following and check the final line in the output:

C:\Users\Administrator>w32tm /query /status
Leap Indicator: 0(no warning)
Stratum: 4 (secondary reference - syncd by (S)NTP)
Precision: -6 (15.625ms per tick)
Root Delay: 0.0314484s
Root Dispersion: 7.7758595s
ReferenceId: 0xA9FEA97B (source IP: 169.254.169.123)
Last Successful Sync Time: 26/03/2020 19:37:22
Source: 169.254.169.123,0x9
Poll Interval: 2 (4s)
30th March 2020

Deploying Route53 Subdomain for a VPC

How to create a Subdomain for a VPC (Eg [vpcname].int.[yourdomain].com).

This is useful for allowing ec2 instances to connect to each other with custom domain names rather than the internal DNS name automatically created by AWS when You create an ec2 instance.

Setting up the Subdomain in Route 53:

  • Open up Route53 Control Panel and Create a new Hosted Zone
    • Enter Your Subdomain (Eg [vpcname].int.[yourdomain].com)
    • Select Type “Private Hosted Zone for Amazon VPC”
    • Select Your VPC ID

Creating a Record:

  • Select Your hosted zone via the Route 53 Hosted Zones Page
  • Click “Create Record Set” at the top of the page
  • Add Your DNS Record (Eg an A record for one of Your EC2 Instances)

Setting up Your DNS Host:

  • With Your Hosted Zone selected in the Route 53 panel, select the NS (NameServer) records and copy the 3 AWS Nameservers from the “value” field on the right hand side.
  • Open up Your DNS Provider and create 3x DNS records with Your subdomain as the Host and the 4 Nameservers provided by AWS as the values for these records.

Enabling the Hosted Zone in Your VPC:

  • Open up the VPC Console and select Your VPC that You setup the Route 53 Endpoint for
  • Go to the Tags page and create the following two tags:
    • enableDnsHostnames: true
    • enableDnsSupport: true

Setting the FQDN Domain for the VPC:

In order to be able to resolve DNS names without the full fqdn (Eg resolving just “db” rather than having to use “db.myvpc.int.mydomain.com”) You need to update the DHCP Option Set for the VPC to provide this Domain via DHCP.

  • Open the VPC Console and select “DHCP Options Set” on the left hand side
  • Click “Create DHCP options set” at the top of the page and create a new Option set with the following settings configured:
    • Name: [Your VPC Name]
    • Domain Name: The full domain You created earlier (Eg [vpcname].int.[yourdomain].com)
    • Domain name servers: AmazonProvidedDNS
    • NTP Servers: 169.254.169.123
  • Go back to the “Your VPC” page and select Your VPC that You setup the Route53 Subdomain for.
  • Go to “Actions” and select “Edit DHCP Options set” and select Your new DHCP Option Set

To immediately test the DNS resolution You can reboot one of Your instances on the VPC and ensure You can ping one of the A records You created.