In a move to put Linux on everything I own, I just installed DD-WRT on my Linksys router. DD-WRT is free Linux-based firmware for several wireless routers, most notably the Linksys WRT54G family. Many of DD-WRT’s features are not included in typical router firmware. These features include support for the Kai network, daemon-based services, IPv6, Wireless Distribution System, RADIUS, advanced quality of service, radio output power control, overclocking capability, and software support for a Secure Digital Card hardware modification.


The Linksys WRT54GL was released in 2005 to support third-party firmware based on Linux. Its fully compatible with DD-WRT. This guide also works for a couple of other LinksysWRT54G, models WRT54G v4 and earlier, but the WRT54GL is the the preferred router to buy/use.
If you want to see what other routers are DD-WRT compatible go here.

BEFORE YOU START:
Use an ethernet cable to connect your PC to your router (use port 1)
DO NOT attempt to use the guide via wifi, you will brick your router.

Step 1: Get Your Router Ready

Type the following into your browser’s URL box:
http://192.168.1.1
Restore your router to its factory settings:
In the Administration tab, under Factory Defaults, select YES and the SAVE the Settings.
Log Back Into Your Router:
http://192.168.1.1
name= *Leave It Blank*
password= admin
Step 2: The Inital Flash
Unzip the dd-wrt.v23_sp2_mini.zip file

Go to Firmware Management, under Administration>Firmware Management.
Select the dd-wrt.v23_mini_generic.bin file
Select UPGRADE to begin the process.


* Do not interrupt the process * make sure the router stays plugged in

You will see an Upgrade Successful screen message
Click CONTINUE.
Step 3: Reset and Flash Firmware Again
Find the reset button on the back of the WRT54GL
Hold down the reset button for 30 seconds
Release the reset button
Allow the lights to blink for 15 seconds
Log Back Into Your Router:
http://192.168.1.1
username= root
password= admin

Download the dd-wrt.v23_generic.bin
Unzip the dd-wrt.v23_sp2_standard.zip file


Go to Firmware Management, under Administration>Firmware Management.
Select the dd-wrt.v23_generic.bin file
Select UPGRADE to begin the process.



* Do not interrupt the process * make sure the router stays plugged in

Find the reset button on the back of the WRT54GL
Hold down the reset button for 30 seconds
Release the reset button
Allow the lights to blink for 15 seconds
Step 4: Login & Setup Your Router
http://192.168.1.1
username= root
password= admin
Source via Ubuntu1501