[CentOS] connecting linux console using serial port (NOW PPP)

israel.garcia at cimex.com.cu israel.garcia at cimex.com.cu
Fri Aug 18 21:33:23 UTC 2006


Alex, thanks for your soon answer, but in case I want to configure PPP
on this server, what files do I have to configure?
Can I login in this server using SSHD over a PPP conection?

Regards;
Israel

> Just terminal access -> I want to login in my linux server connecting
> through the modem connected in /dev/ttyS0

Not sure if this is complete.

Install mgetty if not already present on your system.

Go to /etc/mgetty+sendfax directory.  If you have CallerID feature on  
your phone line (and you should get it if you don't have it yet), edit  
dialin.config file and add telephone numbers you will be dialing from.  
  At least this will prevent clueless script-kiddies from getting  
login prompt on your modem line.  I know that some of my modems get  
regullary probed from strange phone numbers (and those are dedicated  
modem lines -- no voice calls on them, not listed in white pages, too  
often on too many lines to be the simple case of wrong number).

While there, check login.config file.  If you don't want PPP on it,  
make sure /AutoPPP/ is commented (should be default).  Make sure "* -  
- /bin/login @" line is not commented (should be last line in the  
default config file).  That's the line that will give you login prompt.

Edit /etc/inittab and add something like this:
s0:2345:respawn:/sbin/mgetty -D -n 2 -s 115200 /dev/ttyS0

The "-n 2" tells mgetty to pick up the phone after second ring.  You  
need to wait till second ring because telephone company sends CallerID  
information between first and second ring.  If you configured mgetty  
to answer after first ring, it would never get CallerID information.

Execute "telinit q" as root (this tells init process to reread inittab
file).

Configure and connect modem and you should be set to go.  I do not  
recommend allowing root to login directly from modem line (could be  
configured by editing /etc/securetty and /etc/security/access.conf  
files if needed, but not wise idea).  Login as normal user, than su to  
root.

-- 

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