How to connect a CentOS computer to Internet using USB Wifi Adapter ?

I have an old desktop computer with CentOS 7 operating system installed without GUI. I wanted to connect to internet using a USB wifi adapter. My internet router was located in a different room and LAN cable was not available with me. So I used netgear USB wifi adapter for establishing the internet connection. This post is about troubleshooting and fixing the connectivity issue.

The model that I have used is Netgear WNA3100M Wireless-N300 USB Mini Adapter. The picture is shown below.


Netgear WNA3100M

I checked the network interfaces and ip address using ifconfig command. It listed an interface named wlp18s0b1. But no ip address was assigned.

I tried ifup command. But it gave me an error as follows.

ifup wlp18s0b1

/sbin/ifup: configuration for wlp18s0b1 not found.
Usage: ifup 

Then I tried listing the USB interfaces using lsusb command and it listed the network adapter usb device. This means that the device is getting detected.

The next steps that I tried are using the nmcli command.

The following command will list all the available Wifi connection profiles.

nmcli connection show

To connect to a wifi network, use the below command. You have to pass your wifi ssid and password as shown below as arguments.

nmcli dev wifi connect your-wifi-ssid password wifi-password

My desktop got connected to the internet after triggering the above command. After this, every time I start my computer, if the desktop is not automatically connected to the internet, I issue the following commands.

nmcli connection show

nmcli connection up your-wifi-connection

This solution helped me. Hope this will help someone else also :).

SELinux modes – Simple explanation

Everyone who uses linux might be familiar with SELinux. The full form of SELinux is Security-Enhanced Linux. It is a kernel level security module that enhances the access level security policies.

In this post I will be quickly explaining about the various modes in SELinux.

There are three modes in SELinux

  • Enforcing
  • Permissive
  • Disabled

In CentOS and RHEL systems , the SELinux configurations are controlled using the configuration file /etc/sysconfig/selinux.

The changes made to this file needs a system reboot. We can disable the SELinux permanently only with a system reboot. But we can set the SELinux into permissive mode without reboot. This can be easily performed by issuing a setenforce command. The details are explained in my another blog post.

Here we can set SELinux to any of the modes mentioned above.

In the Enforcing mode, SELinux is completely active and it will allow access only using the SELinux policies. User can configure the policies to enable access to their application.

In the Permissive mode, the SELinux will be monitoring and logging all the activities that would have been denied if it is in the enforcing state. The SELinux will not block any activities in this state.

In the Disabled mode, SELinux will be completely disabled.