Showing posts from October, 2015

RHEL7 Fedora as Network Router and Gateway

Hardware Requirements:2 Ethernet Network Cards: 1 for WAN; 1 for LANOptional Wireless Router for wifi
Software Requirements:NIC Configuration Filessysctl Kernel ParametersFirewall Configurationdhcpd Server For the sake of clarity the two network cards will be called ifcfg-wan (WAN) and ifcfg-lan (LAN); make the necessary changes for your environment accordingly, e.g. eth0, ens1, enp0s77, etc., as I will not outline how to make naming changes for hardware devices.  The configuration files for the relevant network adapters/cards are located in /etc/sysconfig/network-scripts/ifcfg-wan and /etc/sysconfig/network-scripts/ifcfg-lan files.

First, make sure all the interfaces are "down" and the ethernet cables are unplugged from both adapters.  Assuming you're not using NetworkManager this can be accomplished on the commandline with "ifdown wan" and/or "ifdown lan".

Next, check the system's network activity for open ports and close them all for now:

# netst…

Troubleshoot USB-Printer Connected to Router

I had complained about a flood of error messages being continuously printed out every time a print job was sent to the USB-printer attached to my Asus AC56U router with merlin-378.55_beta1. Yesterday, after I had reverted to the official asuswrt firmware to troubleshoot the printer-sharing feature, I used nmap on my laptop to see the open common ports on the clients on my network:

Code: # nmap -T4 -F The router displayed two ports related to the printer service:

Code: Host is up (0.0065s latency). Not shown: 94 closed ports PORT STATE SERVICE 53/tcp open domain 80/tcp open http 139/tcp open netbios-ssn 445/tcp open microsoft-ds 515/tcp open printer 9100/tcp open jetdirect Anyway, long story short, I had been using the socket:// path to the printer; changing the configuration on my laptop (CUPS-server) to point to lpd:// finally resulted in SUCCESS!

Linux: Keyboard-Mapping Control

Remapping Keys Given the variations in physical keyboard layouts across personal computers from different manufacturers, the potential for a configured key to be mapped differently than expected or even to be missing on some keyboards creates the need for System Administrators to be able to remedy this problem by remapping the desired functions to the available key(s) of their choosing.  Luckily, there are a number of powerful tools available for the Linux OS, some of which will be outlined in this note with a few usage examples and scenarios.

How to Map the Super key to Search key The Samsung Chromebook doesn't have a Super key, or "Windows" key, on its keyboard; as a result, the Super key, which is usually mapped to it by default, is missing from the keyboard and the user is missing a useful function from certain applications.
    In order to provide the user with a convenient shortcut on their keyboard, first we need to find find out some mo…

Virtual Interfaces and VLANs in Fedora20

Setting up VLAN interfaces in Fedora20 VLAN is an acronym for Virtual Local Area Network. Several VLANs can co-exist on a single physical switch, which are configured via Linux software and not through hardware interface (you still need to configure actual hardware switch too).

Hardware Device Requirements
• To be able to use VLANs you will need a switch that support the IEEE 802.1q standard on an Ethernet network.
• You will also need a NIC (Network Interface Card) that works with Linux and support 802.1q standard. Setting Up 802.1q VLAN Tagging This is based on Fedora documentation, specifically F17-System Administrators Guide .
• First, ensure that the 8021q kernel module is loaded with the following command:
# lsmod | grep 8021q# modprobe 8021q is the command to load it if no output results from the grep command above.
• Configure the physical interf…

How to Connect a TI Graphing Calculator to a Linux PC

This post will document how to install a linking program for a TI-83+ on a Fedora18-x86_64 laptop. The purpose of the program is to be able to connect your Graphing Calculator via a USB TI Connectivity Cable, in order to transfer data to/from your Graphing Calculator. I should mention that I am not in any way affiliated with the developers of any of these programs, and I take no credit for any of its development; this is merely meant to help those who are struggling to install this valuable software on their computers.
What you will NeedTI Graphing Calculator (obviously)Connectivity Cable (GraphLink cable)TILP2 (TI Linking Program)TILIBS (the library files for the program)libglade2-dev, libusbx-devel (development files for certain libraries on your Fedora/Linux computer) Installation I will assume that you already have the calculator and the necessary cables for the remainder of this procedure, and so we will proceed to download the necessary files from That's a g…