Networks Guru

Category: Linux

Using Dual Monitor/Dual Touch Screens on Ubuntu

When using a dual touch screens on ubuntu, the touch may not be mapped correctly to the monitor and it may span both screens as input and only 1 monitor as an output.
Or simply touching any of them will result in having the input on the same screen (Relatively).

So, In order to apply a fix for this issue, The touch input should be mapped to the correct monitor

We may use 2 linux apps to list this info.
1. xinput is used for listing the input devices
2. xrandr is used to show/set the size, orientation and/or reflection of the outputs for a screen. It can also set the screen size.

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Apache – Mapping URL PATH to a Directory on the FileSystem

Well, Mapping a URL Path to a directory can be useful in many scenarios,

Ex:

  • As a proof of ownership, some sites may ask you to publish certain files in certain directories “Google WebSite Ownership Verification, etc…
  •  Publishing Django static files while proxying all the other URLs. Django Developers will relate 🙂
  • etc…

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Creating a dummy Interface on a Linux/Unix based Systems

A dummy interface maybe created for various reasons like:

  • Publishing Services
  • A 2nd loopback interface with a public IP

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Verifying a route on a Linux System

With the existence of the IP package in a linux/unix system the routing table can be viewed using the below command

$ ip route

ex:

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Parsing a list of IPs and/or Networks with Prefix-Length or Subnet Masks

A very simple script that uses ipcalc capabilities to parse a list of IPs or networks an outputs a list of readable Network IDs with their subnet masks.

#!/bin/bash

AUTHOR=AHMED
Blog=”Networks.Guru”

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Changing the Wireless Card’s Transmission Power

The current value of the wireless card’s TX-Power can be verified using the below command

user@pc:~ $ iwconfig
wlan0 IEEE 802.11 ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=22 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:on

user@pc:~ $ iw reg get
country GB: DFS-ETSI
(2402 - 2482 @ 40), (N/A, 20), (N/A)
(5170 - 5250 @ 80), (N/A, 20), (N/A)
(5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS
(5490 - 5710 @ 160), (N/A, 27), (0 ms), DFS
(57000 - 66000 @ 2160), (N/A, 40), (N/A)

The Tx-Power value is in dBm “Decibel (referenced to milliwatts)” This value can be converted to milliwatts using this function

P(mW) = 1mW â‹… 10(P(dBm)/ 10)

Before changing the value of the Tx-Power, You need to make sure that you comply with the legal limits within your country and you’ll not end up frying the wireless card

The below commands can be used to change the current value of the transmission power

The max value cannot be set over the limit specified by the assigned country’s regulations

So, for education Purpose only the country may be set to a country allowing higher Transmission power “ex: Bolivia <BO>”

 

ifconfig wlan0 down
iw reg set BO
ifconfig wlan0 up
iwconfig wlan0 txpower 30

 

So,  By verifying the results of the last commands, we see that the values have been set successfully

user@pc:~ $ iwconfig wlan0
wlan0 IEEE 802.11 ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=30 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:on

user@pc:~ $ iw reg get
country BO: DFS-JP
(2402 - 2482 @ 40), (N/A, 20), (N/A)
(5250 - 5330 @ 80), (N/A, 30), (0 ms), DFS
(5735 - 5835 @ 80), (N/A, 30), (N/A)

 

 

 

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