How to configure UNIX or Linux for administration via serial connection

Question

How can I configure my UNIX or/and Linux PC with COM port to support serial console connections? I would like to connect my notebook to that PC via a console cable and manage the PC with terminal emulation software like putty, as if I use keyboard directly.

Answer 1

I have this line in /etc/inittab on a server I run that has a serial console:

T0:23:respawn:/sbin/getty -L ttyS0 57600 vt100

ttyS0 is the serial port. That's all there is to it, at least here.

Edit: You'll probably want something like this in your grub.conf:

serial --unit=0 --speed=57600
terminal --timeout=10 serial console

And then with each kernel:

kernel /boot/vmlinuz ro root=/dev/md1 console=tty0 console=ttyS0,57600

(The important part is the console= arguments)

Answer 2

In addition to the other answers, I'd suggest looking here:

http://tldp.org/HOWTO/Remote-Serial-Console-HOWTO/

Specifically, the GRUB section so that you can get the boot menu too (not just the OS once it begins to load):

http://tldp.org/HOWTO/Remote-Serial-Console-HOWTO/configure-kernel-grub.html

Answer 3

See the other answers if your distro uses inittab. But Ubuntu uses /etc/event.d and most other distros are or will as they adopt the more modern init daemon Upstart. At least it will eventually get rid of those hideous System V "run levels".

If you do have a /etc/event.d/, in there you should have tty1, tty2, .... You may need to copy one of the tty files to ttyS0. (Check /proc/devices to see what you have.)

These files look something like:

# tty1 - getty
#
# This service maintains a getty on tty1 from the point the system is
# started until it is shut down again.

start on stopped rc2
start on stopped rc3
start on stopped rc4
start on stopped rc5

stop on runlevel 0
stop on runlevel 1
stop on runlevel 6

respawn
exec /sbin/getty 38400 tty1

Be sure the device name and the speed are what you want.

Answer 4

You just tell the machine you want to connect to with the serial console to listen on a serial port. Most Linux distributions come with examples in their /etc/inittab files that show how to do it (look for /dev/ttyS0).