Author: Noel Alvarez

Domain Name System – Propagation

May 10, 2018
BINDDomain Name SystemNetwork

I recently decided to test a Domain Name System (DNS) provider expansion with GoDaddy and  ClouDNS (link here) for a proof of concept using the domain name noelalvarez.org. The initial configuration and testing were successful. However, after I made the decision to host all DNS service with GoDaddy (again, it was a proof of concept) I found a large quantify of name server around the globe contained name server (NS) records for noelalvarez.org with entries pointing to ClouDNS name servers (ns21.cloudns.net, ns22.cloudns.net, ns23.cloudns.net, and ns24.cloudns.net) using Whats My DNS? (link here). I found this odd due to the fact that the GoDaddy DNS management interface only contained (2) NS records (ns57.domaincontrol.com and ns58.domaincontrol.com) which are the authoritative for the domain noelalvarez.org and the ClouDNS name servers are no longer hosting zone files or responding to DNS queries for noelalvarez.org. Additionally, the Time to Live (TTL) was a maximum of (1) hours. So, I didn’t expect to find inconsistencies days later.

So, what could be causing the lack of synchronization in the NS records (remember, DNS is a distributed and hierarchial system by nature)? Upon basic troubleshooting I found that the GoDaddy name servers ns57.domaincontrol.com and ns58.domaincontrol.com did not contain the same NS records for noelalvarez.org using the nslookup utility (please see the screen shots below). I have contacted GoDaddy support and they have provided me with assurance that they will manually delete the NS records of ns21.cloudns.net, ns22.cloudns.net, ns23.cloudns.net, and ns24.cloudns.net from ns57.domaincontrol.com.

VMware Workstation 11 – Boot from USB Drive

April 13, 2018
VMware Workstation 11

You may use the steps below to boot a virtual machine (VM) in VMware Workstation 11 from a USB drive.

  1. Select VM > Settings.
  2. Select the Options tab.
  3. Select the Advanced setting.
  4. Enable Boot with EFI instead of BIOS.
  5. Click OK.

VMware vCenter Server 6.0 – Verify the Status of Critical Services Locally

November 22, 2017
AutomationMicrosoft Windows PowerShellScriptingServicesVMware vCenter Server 6.0VMware vSphere 6.0

The script below will query the status of the service(s) specified in “C:\Scripts\VMware vCenter Server\Verify_Critical_Services.txt” on the local server. The output of the script will provide the name and status of the service(s) in a formatted list for your viewing. Additionally, it is recommended that the following services be queried as they are critical to the proper functioning of VMware vCenter Server 6.

  • VMware VirtualCenter Server (vpxd)
  • VMware Inventory Service (invsvc)
  • VMware vSphere Web Client (vspherewebclientsvc)

<#
.SYNOPSIS
This script will provide the name and status of the service(s) defined in “C:\Scripts\VMware vCenter Server\Verify_Critical_Services.txt”
.DESCRIPTION
This script will automate the process of providing the status of critical VMware vCenter Server 6 service(s) on the local server
.EXAMPLE
N/A.
.AUTHOR
Written by Noel Enrique Alvarez on Wednesday, November 22, 2017.
#>

#Define the service(s) to query
$Services = Get-Content “C:\Scripts\VMware vCenter Server\Verify_Critical_Services.txt”

#Query the status of the service(s) in “C:\Scripts\VMware vCenter Server\Verify_Critical_Services.txt”
ForEach ($Service in $Services)
{Get-Service $Service |
Format-List -Property Name, Status}

Red Hat Enterprise Linux 7 – Banner

September 9, 2017
Red Hat Enterprise Linux 7

While logging into a Red Hat Enterprise Linux 7 server by means of SSH you may be addressed by a login banner. You may use the steps below to create the login banner.

  1. Edit the /etc/ssh/sshd_config file (i.e. Banner /etc/banner)
  2. Create the /etc/banner file
  3. Restart the SSH service (i.e. systemctl restart sshd)

Apache – Simple Maintenance Page

September 7, 2017
Apache

You may use the following sample maintenance page for your website, when necessary. I did not create it but I did find it very helpful and the link to the HTML code may be found here.

<!doctype html>
<title>Site Maintenance</title>
<style>
body { text-align: center; padding: 150px; }
h1 { font-size: 50px; }
body { font: 20px Helvetica, sans-serif; color: #333; }
article { display: block; text-align: left; width: 650px; margin: 0 auto; }
a { color: #dc8100; text-decoration: none; }
a:hover { color: #333; text-decoration: none; }
</style>

<article>
<h1>We&rsquo;ll be back soon!</h1>
<div>
<p>Sorry for the inconvenience but we&rsquo;re performing some maintenance at the moment. If you need to you can always <a href=”mailto:#”>contact us</a>, otherwise we&rsquo;ll be back online shortly!</p>
<p>&mdash; The Team</p>
</div>
</article>

Red Hat Enterprise Linux 7 – Message of the Day

July 27, 2017
Red Hat Enterprise Linux 7

You may use the following example as a Red Hat Enterprise Linux (RHEL) 7 message of the day (MOTD). This file is located at /etc/motd.

#########################################################################
# For Authorized Use Only #
# #
# Activities on this system are subject to being monitored #
# or recorded for all users, authorized or unauthorized. #
# Use of the system is considered consent to such monitoring. #
# Any evidence of possible criminal activity may be provided #
# to law enforcement. #
# #
#########################################################################

VMware ESXi 6.0 – Syslog Collector Configuration

March 24, 2017
VMware ESXi 6.0

VMware ESXi 6.0 hosts save their log files locally by default. However, you may configure the host to save their logs to a centralized server known as the Syslog Collector. Below are the steps to complete the configuration.

  1. Start the SSH service on the VMware ESXi 6.0 host.
  2. Enter the following command to configure the syslog collect on the host esxcli system syslog config set –loghost=x.x.x.x –logdir-unique=true. The –loghost=x.x.x.x value identifies the Syslog Collector server.
  3. Enter the following command to enable the syslog collector configuration esxcli system syslog reload.
  4. Stop the SSH service on the VMware ESXi 6.0 host.
  5. Configure the firewall to allow the outgoing traffic.
  6. After the host is added to vCenter server verify the logs are located in the following directory on the Syslog Collector server C:\ProgramData\VMware\vCenterServer\data\vmsyslogcollector.

VMware ESXi 6.0 – Dump Collector Testing

March 24, 2017
VMware ESXi 6.0

The VMware ESXi Dump Collector is a centralized service that can receive and store memory dumps from VMware ESXi 6.0 hosts in the event that they crash unexpectedly. In order to use this feature you must first configure the VMware ESXi Dump Collector Service. Then, you must configure the VMware ESXi 6.0 host to redirect their memory dumps. After the VMware ESXi 6.0 host has been configured to redirect their memory dumps you may use the commands below to verify test the configuration.

  1. Start the SSH service on the VMware ESXi 6.0 host.
  2. Enter the following command  to send a test dump to the collector esxcli system coredump network check.
  3. On the dump collector server, in the %ProgramData%\VMware\VMware ESXi dump collector\Data\ folder, verify that a new dump file is present (i.e. IP address of the VMware ESXi 6.0 host).
  4. Stop the SSH service on the VMware ESXi 6.0 host.

VMware ESXi 6.0 – Dump Collector Configuration

March 22, 2017
VMware ESXi 6.0

The VMware ESXi Dump Collector is a centralized service that can receive and store memory dumps from VMware ESXi 6.0 hosts in the event that they crash unexpectedly. In order to use this feature you must first configure the VMware ESXi Dump Collector Service on VMware vCenter Server. Then, you use the commands below to configure the VMware ESXi 6.0 host to redirect their memory dumps.

  1. Start the SSH service on the VMware ESXi 6.0 host.
  2. To review the existing  dump collector configuration enter the command esxcli system coredump network get and press Enter.
  3. Configure the VMware ESXi 6.0 host’s dump redirection with the following command esxcli system coredump network set -v vmk0 -i x.x.x.x -o xxxx. The -i option is used to specify the IP address of the dump collector and the -o option is used to indicate the dump collector port number.
  4. Enter the following command to turn on dump redirection esxcli system coredump network set -e true.
  5. Enter the following command to confirm the dump redirection settings esxcli system coredump network get.
  6. Stop the SSH service on the VMware ESXi 6.0 host.

Microsoft Active Directory – Get NetBIOS Name

February 15, 2017
AutomationMicrosoft Active DirectoryMicrosoft Windows PowerShell

You may use Microsoft Windows PowerShell to obtain the NetBIOS name of a Microsoft Active Directory (AD) domain. The command is Get-ADDomain –Identity domain.com and the NetBIOS name is contained in the NetBIOSName field.