This is a simple setup guide to enabling Two Factor Authentication (2FA) on Linux SSH login. I this article I wont go deep into setup and issues that I have faced when implementing this. First thing is first Update your system first. I have used Ubuntu 20.04 and it is always up to date. To enable 2FA you need to install google authenticator modules sudo apt install libpam-google-authenticator Configuration for PAM and SSHD Add the the following line to /etc/pam.d/sshd and After adding this line please restart the sshd services. auth required pam_google_authenticator.so Go to /etc/ssh/sshd_config and check if the following line exist. Default value will be "no" so change it to "yes" to activate. ChallengeResponseAuthentication yes Configuration for Authenticator In the terminal run google authenticator command It will ask few things to acknowledge by user. Details you can see from the below video. Once this part is done you are ready to use the 2FA in ubuntu. T
I always have interest in electronics and i think in 1994 i got an physics book from some where that i don't remember now. Everyday after school i read it and got more interested on it even though i don't understand what its all about. Day by day small radios are disassembled and experimented how it works and able to fix the issues.
When i was in grade eight till ten i don't have any interest in studying any subject that i feel useless. More and more focus to physics and math but 99% is always physics specially the electronics chapters.
Couple of friends from school know that i know electronics some how and we share what we built and ideas. Those days Internet or PC is not available for me but a friend have i PC and i used to visit him and he knows some computer skills. we spent time on dial-up Internet in IRC. :)
One day my physics teacher asked me do you like electronics? i said yes i do and i want to learn more. So he told if you love electronics i can help you to meet his VTC student, a great guy and now a good friend of mine too. He is like a electronics father to me so i told my other friend that i met a guy who is really good in electronics and let me introduce you to him too. So we meet him after school at electronics guy's office. So we all meet and he took us to his work shop and gave some books to learn, most of the things was in the physics textbook but i took it. After a week i learn general components, color codes and more. My friend got into more computer programming and me into electronics.
I always remember what my electronics teacher said. "Don't jump into digital electronics without knowing basics and analog electronics" so everyday i learn Transistors and transistors are the beginning of IC's. All most all semiconductors covered. Everyday circuits and a breadboard given to me to do my practice. Finally i manage to transfer to analog electronics , playing with sound waves , light waves , infrared etc. Able to use first timer (555 timer IC) ever built and still its used in most electronics applications. Op-amps like 741 by fair child was an legendary IC i have used. After an year learn digital electronics, logic gates which makes things difficult when combining two different types of electronics.
Luckily i was able to join MITE to learn more theory and graduated being the first in electronics batch. Sometimes now also invited me to come there to help new guys but due to my busy schedule of experimenting stuff i was not able to go there.
Later my friends and me spent more time on experimenting and found a cheaper micro controller by Microchip which built as a kit by Mikroelektronica a Belgrade company so we order some chips and since the programmers are bit expensive we built a programmer by our self and started playing with it. Before that we make programs from Qbasic and control the PC parallel port and that was fun.
If i want to learn microelectronics i need to learn to right some code. So i started with Assembly language which was tough to newbie on programming. After couple of months on 2002 i wrote my first fully functioning ASM code for a customer (Dhiraagu) to control a ventilation fan of some storage area. Here it is and this was my first ever micro-controller program that i wrote. :)
list p=16f84a
#include p16f84a.inc
__config _wdt_off & _xt_osc
cblock 0x0c
jumper1,jumper2,delaystart,CNTMSEC,fourmsec,temp
endc
org 0x00
call mainsetup
call setport
call jumpertest
goto main
org 0x04
goto isr
setport
bsf status,rp0
movlw b'00011111'
movwf trisa
movlw b'00000001'
movwf trisb
bcf status,rp0
return
jumpertest
movfw porta
movwf jumper1
movwf jumper2
clrf delaystart
return
mainsetup
bsf intcon,7 ;global interrupt enable
bsf intcon,4 ;rb0 intrrupt enable
bcf intcon,1
return
; isr code
isr
bcf INTCON,GIE ; Disable all interrupts
; btfsc INTCON,GIE ; goto ISR
bsf delaystart,0
movfw jumper1
movwf jumper2
bcf INTCON,INTF ; Clear interrupt fleg RB0/INT
RETFIE ; Enable all interrupts
; 1sec delay
secdelay
call DLY20
decfsz fourmsec,0
goto secdelay
return
maindelay call outhigh movlw 4
movwf fourmsec
skpz jumper2 decf jumper2
skpz jumper2 call secdelay
goto maindelay
clrf delaystart
return
outhigh
movlw 0x02
movwf portb
return
outlow
movlw 0x00
movwf portb
goto main
DLY20 MOVLW d'250'
NMSEC MOVWF CNTMSEC
MSECLOOP MOVLW D'248'
CALL MICRO4
NOP
DECFSZ CNTMSEC,f
GOTO MSECLOOP
RETURN
ONEMSEC MOVLW D'249'
MICRO4 ADDLW H'FF'
BTFSS STATUS,Z
GOTO MICRO4
RETURN
main
btfsc delaystart,0
call maindelay
goto outlow
end
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