Wednesday, 16 August 2017

Creating an internal / NAT'd network using a vSwitch on Server 2012 / 2016

We'll firstly need to install the Hyper V role - since we'll require the management tools in order to create our interface:

Install-WindowsFeature Hyper-V –IncludeManagementTools
Install-WindowsFeature Routing -IncludeManagementTools

However I had the following message returned when attempting installation:

Hyper-V cannot be installed: A hypervisor is already running.

As I was running under VMWare I had to install the feature using a slightly different method (bare in mind we have no intention of using the Hyper V hypervisor - however we do want to take advantage of the virtualized networking capabilities.

So instead I installed Hyper with:

Enable-WindowsOptionalFeature –Online -FeatureName Microsoft-Hyper-V –All -NoRestart

and the management tools with:

Install-WindowsFeature RSAT-Hyper-V-Tools -IncludeAllSubFeature

Ensure the NAT routing protocol is available to RRAS - 'Administrative Tools' >> 'Routing and Remote Access' >> Expand the following: Server, IPv4 and right hand click on general and select 'New Routing Protocol' >> Select NAT

We can now create our new virtual switch with:

New-VMSwitch -SwitchName "SwitchName" -SwitchType Internal

and assign the interface with an IP:

New-NetIPAddress -IPAddress -PrefixLength 16 -InterfaceIndex <id>

(You can get the associated interface index with: Get-NetAdapter)

At this point you won't be able to ping any external hosts from that interface - we can verify that using the '-S' switch with ping:

ping -S

So - we'll need to enable NAT with:

New-NetNat -Name "NATNetwork" -InternalIPInterfaceAddressPrefix

and then attempt to ping from the interface again:

ping -S

Wednesday, 9 August 2017

Useful find command examples in Linux

The below is a compilation of 'find' commands that I often use myself.

Finding files greater (or small) than 50mb

find /path/to/directory -size +50m

find /path/to/directory -size -50m

Finding files with a specific file extension

find /path/to/directory -name "prefix_*.php"

Finding files (or folders) with specific permissions

find /home -type f -perm 777

Finding files that have been changed  in the last hour

find / -cmin -60

Performing an action with matched files (-exec switch)

find / -cmin -60 -exec rm {} \;

Saturday, 5 August 2017

Adding a custom / unlisted resolution in Fedora / CentOS / RHEL

Sometimes I find that xrandr doesn't always advertise all of the supported resolutions for graphic cards - this can sometimes be down to using an unofficial driver or an older one.

However in Fedora the latest drivers are usually bundled in for Intel graphics cards - unfortunately xrandr is only reporting that one resolution is available:

xrandr -q

Screen 0: minimum 320 x 200, current 1440 x 900, maximum 8192 x 8192
XWAYLAND0 connected (normal left inverted right x axis y axis)
   1440x900      59.75 +

In order to add a custom resolution we can use the 'cvt' utility - this calculates the VESA Coordinated Video Timing modes for us.

The syntax is as follows:

cvt <width> <height> <refreshrate>

for example:

cvt 800 600 60

# 800x600 59.86 Hz (CVT 0.48M3) hsync: 37.35 kHz; pclk: 38.25 MHz
Modeline "800x600_60.00"   38.25  800 832 912 1024  600 603 607 624 -hsync +vsync

We then create a new mode with (appending the above in bold):

sudo xrandr --newmode "800x600_60.00"   38.25  800 832 912 1024  600 603 607 624 -hsync +vsync

and then adding that mode to the display (in our case this is WAYLAND0):

sudo xrandr --addmode VGA-0 800x600_60.00

and then set this mode with:

sudo xrandr --output VGA1 --mode 1280x1024_60.00

Wine: Could Not Initialize Graphics System. Make sure that your video card and driver are compatible with Direct Draw

For anyone else getting this problem when attempting to run older games on Wine - in my case this due to the graphics card not supporting the native resolution of the game (800x600) - you can check supported resolution types with:

xrandr -q

However you might be able to add custom resolutions as well.

Otherwise within the Wine configuration you will need to ensure 'Emulate a virtual desktop' is ticked and the appropriate resolution for the game is set.

Monday, 31 July 2017

Mac Book Air: Installing the Broadcom BCM4360 - 14E4:43A0 module on Fedora

Firstly confirm you have the appropriate hardware version (there are two for the BCM4360!)

lspci -vnn | grep Net

The 'wl' module only supports the '14e4:43a0' version.

The RPM fusion repository have kindly already packaged it up for us - so let's firstly add the repo:

sudo dnf install -y

sudo dnf install -y broadcom-wl kernel-devel
sudo akmods --force --kernel `uname -r` --akmod wl
sudo modprobe -a wl

Thursday, 27 July 2017

curl: 8 Command Line Examples

curl is a great addition to any scripter's arsenal and I tend to use it quite a lot - so I thought I would demonstrate some of its features in this post.

Post data (as parameters) to url

curl -d _username="admin" -d password="<password>"

Ensure curl follows redirects

curl -L

Limit download bandwidth (2 MB per second)

curl --limit-rate 2M -O

Perform basic authentication

curl -u username:password https://localhost/restrictedarea

Enabling debug mode

curl -v https://localhost/

Using a HTTP proxy

curl -x

Spoofing your user agent

curl -A "Spoofed User Agent"

Sending cookies along with a request

curl -b cookies.txt

Wednesday, 26 July 2017

Windows Containers / Docker Networking: Inbound Communication

When working with Windows Containers I got a really bad headache trying to work out how to setup inbound communication to the container from external hosts.

To summerize my findings:

In order to allow inbound communication you will either need to use the '--expose'  or  '--expose' a long with  '--ports' switch - each of them do slightly different things.

'--expose': When specifying this Docker will expose (make accessible) a port that is available to other containers only

'--ports':  When used in conjunction with '--expose' the port will also be available to the outside world.

Note: The above switches must be specified during the creation of a container - for example:

docker run -it --cpus 2 --memory 4G -p 80:80 --expose 80 --network=<network-id> --ip= --name <container-name> -h <container-hostname> microsoft/windowsservercore cmd.exe

If your container is on a 'transparent' (bridged) network you will not be able to specify the '-p' switch and instead if you will have to open up the relevant port on the Docker host a long with the '--expose' switch in order to make the container accessible to external hosts.