Enable NTP Server in Windows 2019

The Windows Time service uses the Network Time Protocol (NTP) to help synchronize time across a network. It’s as easy as 3 commands using powershell:

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\w32time\TimeProviders\NtpServer" -Name "Enabled" -Value 1
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\services\W32Time\Config" -Name "AnnounceFlags" -Value 5 
Restart-Service w32Time

Check nvme health and temperature – nvme-cli

Make sure nvme-cli is installed:

$ sudo apt install nvme-cli

Check for availible nvme disks:

$ sudo nvme list
Node             SN                   Model                                    Namespace Usage                      Format           FW Rev  
---------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- --------
/dev/nvme0n1     S4EVNFXXXXXXXX9972H      Samsung SSD 970 EVO Plus 500GB           1          26,60  GB / 500,11  GB    512   B +  0 B   2B2XXXXXM7

With nvme-cli you can now check the internal temperature, disk usage, power cycles, and much more:

$ sudo nvme smart-log /dev/nvme0
Smart Log for NVME device:nvme0 namespace-id:ffffffff
critical_warning                    : 0
temperature                         : 40 C
available_spare                     : 100%
available_spare_threshold           : 10%
percentage_used                     : 0%
data_units_read                     : 90935
data_units_written                  : 119679
host_read_commands                  : 4491381
host_write_commands                 : 2370351
controller_busy_time                : 8
power_cycles                        : 34
power_on_hours                      : 9
unsafe_shutdowns                    : 1
media_errors                        : 0
num_err_log_entries                 : 0
Warning Temperature Time            : 0
Critical Composite Temperature Time : 0
Temperature Sensor 1                : 40 C
Temperature Sensor 2                : 38 C
Thermal Management T1 Trans Count   : 0
Thermal Management T2 Trans Count   : 0
Thermal Management T1 Total Time    : 0
Thermal Management T2 Total Time    : 0

Ubuntu 18.04 – OpenVPN Server in less then 5 minutes

OpenVPN provides flexible VPN solutions to secure your data communications, whether it’s for Internet privacy, remote access for employees, securing IoT, or for networking Cloud data centers. Our VPN Server software solution can be deployed on-premises using standard servers or virtual appliances, or on the cloud.

Prepare your system

Make sure all latests packages and updates have been installed:

$ sudo apt update
$ sudo apt upgrade
$ sudo apt dist-upgrade

Download and run installation script

$ wget https://git.io/vpn -O openvpn-install.sh
$ sudo chmod +x openvpn-install.sh
$ sudo ./openvpn-install.sh 

The script will ask you some questions for it’s basic configuration.
– When your IP address is asked, choose your WAN (public) address
– When protocol is asked, i recommend default UDP
– Port can be anything you want, i normally keep default
– When asked, pick 1.1.1.1 as your DNS server as this is one of the fastest currently online.

After this the installation will go ahead and inform you when it’s done. You can verify if OpenVPN is running or not:

$ sudo systemctl status openvpn@server # <--- get server status

You can start or stop OpenVPN with the following commands:

$ sudo systemctl stop openvpn@server # <--- stop server
$ sudo systemctl start openvpn@server # <--- start server

Client configuration

At the end of the installation you whould see a message like this:

Your client configuration is available at: /root/bontekoe.ovpn

As i am using Linux (Ubuntu) on my laptop, i can simply copy that ovpn file to my computer using scp.

$ sudo scp root@88.99.189.27:/root/bontekoe.ovpn /etc/openvpn/client.conf

This should be enough to connect! Check if everything is working by running:

$ sudo openvpn --client --config /etc/openvpn/client.conf

Now, by opening another terminal you should be able to ping 10.8.0.1 (the VPN host).

If you are running windows, there is a client here.

Ubuntu 18.04 – Laggy bluetooth

After installing this version my mouse became laggy and also my headphones. Here is the fix:

# HANDLE="$(hcitool con | grep '<Bluetooth Mouse mac address>' | awk '{print $5}')"  # get the device handle
# hcitool lecup --handle $HANDLE --latency 0 --min 6 --max 8

Network Monitoring – Traps vs. Polling

As a network administrator, I have been (partly) responsible for the monitoring of network infrastructures or even entire companies for many customers. For some companies I have even completely redesigned it.

Many companies currently use tools such as Nagios, Solarwinds or a similar package. These tools are ( at least, in my opinion) a first-generation software package because it takes a lot of time to set the triggers (in particular). If you also have to deal with different vendors, it becomes even more complex; every vendor has its own event codes and descriptions, which causes unequal and therefore unclear alerts.

Many parties also rely on the use of SNMP Traps. Although you will not be able to completely disable SNMP-Traps, relying on (only) these traps is dangerous. This has various reasons.

Why we cannot trust SNMP Traps

SNMP Traps work on the basis of UDP and is a single datagram which is sent by the device. Consider for example a temperature that exceeds the limit, for which a switch will send a single UDP datagram once. However, UDP does not work in the same way as TCP, because there is no check whether the UDP datagram has ever arrived. TCP has TCP Retransmissions for this, UDP has no control whatsoever.

In the real world, it can happen that a switch gets into trouble due to (for example) spannig-tree recalculation and the SNMP-Trap does not arrive as a result. These notifications will not be sent again and will never be registered. Same thing is the connection between your monitoring host and the device is unstable. Not something you can count on in the event of disruptions.

Next-generation alerts

As I wrote above, I see the mentioned software packages as first-generation monitoring, this is mainly due to the method of generating alerts. For example, alerts are often set that go off when the bandwidth consumption of a gigabit interface is used for 90% or when a hard disk has only 20% space left.

But is it useful to know that bandwidth is going through that specific interface? Maybe someone is watching a video on Netflix that first has to buffer. Is it useful to know that a hard drive only has 20% space left? If it is a small disk it might, but if it’s a 2TB disk then this does not seem worth mentioning.

Future-proof approach to Monitoring and Alerts

The only way to generate correct alerts, which actually require action, is based on metrics. Metrics, metrics and i say again: metrics. You can collect these metrics via SNMP Polling on the devices and with the collected data a trend line can be mapped out. Using the above-mentioned examples, we can determine on the basis of a trend analysis whether there is more often 90% consumption on the Gigabit interface. We can also determine how long it takes before a disk is really full and whether it requires action now.

Doors are opened by collecting metrics. Much more insight into what is happening on the infrastructure, outages can be prevented instead of resolved, better advice can be given in regards to capacity and growth path and it makes it easier for administrators.

The last huge difference is that all alerts are displayed on the same (unique) way. We are no longer dependent on the different vendors!

Steps to improve or setup network monitoring

  1. Draw the network infrastructure in a real-time map view
    No network administrator likes to make network drawings. Make it fun by playing with the real-time display of trends and data and at the same time gain insight into the network and up-to-date documentation.
  2. Transform from network monitoring to service and chain monitoring
    By gaining insight into the ultimate availability of the service, it is also clear what the impact is for the customer
  3. Reclassification of alerts based on impact.
    Considering point 2, we now know what the impact is for a customer. Many services are performed redundantly, so that the impact is less. Combine this with point 1 and you have a real-time view of where the disruption occurs without first having to search for half an hour on the various equipment.
  4. Create a performance baseline
    By measuring the services of the customer on performance (response time) in combination with the availability and response time of the network, it can quickly be determined whether there is a congestion.
  5. Work with trend analysis and forecast alerting
    By making use of all collected data, many false alerts can be prevented. With this data an indication can also be made about capacity and availability in the future.

Benchmarking SSDs with fio

Fio which stands for Flexible I/O Tester is a free and open source disk I/O tool used both for benchmark and stress/hardware verification that i mainly use for benchmarking ceph or specific ssd harware.

When using an SSD make sure it’s pre-warmed. This can be done using the dd command:

dd if=/dev/zero of=/dev/xvdb bs=100M &

After this you can start performance measurement with fio. My advice is to run this test for 6 to 8 hours in order to get real data out of it.

fio --filename=/dev/nvmeXnXpX --direct=1 --rw=randwrite --refill_buffers --norandommap --randrepeat=0 --ioengine=libaio --bs=128k --iodepth=16 --numjobs=1 --time_based --runtime=86400 --group_reporting –-name=benchtest

This command will run for 24 hours and perform write-only workload of 128k blocks on a single process.

Random Read test

sudo fio --name=randread --ioengine=libaio --iodepth=16 --rw=randread --bs=4k --direct=0 --size=512M --numjobs=4 --runtime=240 --group_reporting

This will use 4 processes, run for 2 minutes and only perform read iops.

Random Write test

sudo fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test --filename=random_read_write.fio --bs=4k --iodepth=64 --size=4G --readwrite=randrw --rwmixread=75

This will to a read/write test on a 4 GB file.

Ansible through Ubuntu (WSL) on Windows 10

Windows Subsystem for Linux (WSL) allows you to run Linux straight from your Windows Desktop. I use this on a daily basis for running Ansible scripts without having to install VM’s. Make sure you installed al latest updates.

Enable WSL feature

Open up a Powershell box as Administrator (search powershell, right click and run as Administrator).

Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux

This will initiate the installation and once finished ask if you would like to reboot your system. Go ahead and do that. When the reboot is done search for ‘bash’ and open that, it will first require a few anwsers. Simply fill out all the questions and once that is done you will have Ubuntu up and running.

Install Ansible

Now you are basicly in a Linux environment so you can install Ansible the typical way. Again, in the ‘bash’ window of course, use these instructions:

sudo apt-get -y install python-pip python-dev libffi-dev libssl-dev
sudo pip install ansible

Should you get any permission errors (i did not have this time, but given the nature of how WSL works that could happen) install pip with the –user flag. This will cause it to install ansible in the users home dir, not globally.

You are done. Using the following command you can check what ansible version is now installed:

ansible --version

If you need the most recent version check out my other post here.

Install latest version ansible on Ubuntu 16.04 / 18.04

Ubuntu doesn’t ship with the newest version of ansible out of the box, sadly. You have to manually configure the PPA on your system in order to upgrade to the stable version. Follow these commands to install the PPA:

$ sudo apt update
$ sudo apt upgrade
$ sudo apt install software-properties-common
$ sudo apt-add-repository ppa:ansible/ansible

Hit Enter when asked, and once the process is done update your apt repos:

$ sudo apt update

Now you can either upgrade or simply install ansible:

$ sudo apt install ansible

This should be all, use the following to verify the ansible version:

$ ansible --version

Ubuntu 18.04 resize/expand (root) filesystem

Running Ubuntu 18.04 i ran out of disk space on my main partition. I increased disk space in VMware and needed to expand the partitions from within Ubuntu. Start with scanning for changes on your disk

echo 1 > /sys/class/block/sda/device/rescan

Verify that you can see the new (correct) disk space using:

fdisk -l

Create a new partition using “cfdisk”, navigate to the free space and hit “new”. After that hit Write to make sure the partition table gets written. Close cfdisk and either reboot or rescan to update your partition table. Now it’s time to add the disk space. First, find the new partition number:

fdisk -l

In my case sda3 was created to i’m going to create a new volume on it

pvcreate /dev/sda3

now extent my volume group with the newly added volume:

vgextend ubuntu-dev-box /dev/sda3

Extend the volume with all available (new) disk space:

lvextend -l+100%FREE /dev/ubuntu-dev-box/root

Now resize the filesystem:

resize2fs /dev/mapper/ubuntu--dev--box--root

SSH Tunnel to watch Netflix

I often use a ‘hopping server’ when connecting to clients, that means i need to login twice each time. To make my life easier i sometimes use an SSH tunnel so i can connect to clients directly.

SSH Tunnel can also be usefull when your office blocks netflix 😉

Local Port Forwarding

This will allow you to access remote servers direcly from your local computer. Let’s assume you want to use RDP (3389) to a clients hosts (10.0.1.1) and your hopping server is ‘hopping.server’

ssh -L 6000:10.0.1.1:3389 wieger@hopping.server

Now you can open Remote Desktop and connect to ‘localhost:6000’, directing you through the tunnel!

Remote Port Forwarding

This will make your local service/port acccessible from a remote host. Sometimes i use this to keep a ‘backdoor’ and login remotely (home or whatever).

Let’s say you want to make a webapplication (TCP 443) availible at port 6000 on the remote SSH server

ssh -R 6000:localhost:443 wieger@bontekoe.technology

Now you should be able to connect to port 6000 on the remote host (bontekoe.technology)

Dynamic Forwarding (Proxy)

This is ideal for people who want to use the internet safely/anonymous or for offices where Netflix is blocked 😉

Use a remote server to tunnel all web traffic (eg. home server), connect through SSH to it using the -D flag

ssh -D 6000 wieger@bontekoe.technology

Now open up your browser settings, navigate to the connection properties and enter a Proxy server (manually using SOCKS). Use 127.0.0.1 as host and 6000 as port. The tunnel will remain open as long as you are connected through SSH.