To setup a serial console you need to edit the following files under Debian Linux:
- /boot/grub/menu.lst or /etc/default/grub (recommended for grub2)
- /etc/inittab
- /etc/securetty
Our Setup
You can list your working serial port under Linux as follows:# setserial -g /dev/ttyS[0123]
Sample outputs:
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4/dev/ttyS0 (COM1) is detected and working serial console under Linux. For testing purpose, I'm going to set baud rate to 19200 and terminal type to vt100.
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
Grub Configuration (Grub2)
Edit /etc/default/grub, enter:# vi /etc/default/grub
Append / modify as follows:
GRUB_CMDLINE_LINUX='console=tty0 console=ttyS0,19200n8'Save and close the file. Next run the following command to generate a grub2 config file /boot/grub/grub.cfg :
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=19200 --unit=0 --word=8 --parity=no --stop=1"
# update-grub
A Note About Grub Legacy (older version)
If you are not using GRUB2 update /boot/grub/menu.lst (grub legacy) with kernel line as follows with console port, and baud rate:title Debian GNU/Linux, kernel 2.6.32-5-486Save and close the file.
root (hd0,0)
kernel /boot/vmlinuz-2.6.32-5-486 root=UUID=b598f856-2a2a-46d5-b60a-95826cfc7bf6 ro console=ttyS0,19200 earlyprint=serial,ttyS0,19200
initrd /boot/initrd.img-2.6.32-5-486
/etc/inittab Configuration
Edit /etc/inittab, enter:# vi /etc/inittab
You need put a getty on a serial line for a terminal:
T0:23:respawn:/sbin/getty -L ttyS0 19200 vt100Save and close the file.
/etc/securetty Configuration
Edit /etc/securetty, enter:# vi /etc/securetty
Make sure UART serial ports /dev/ttyS0 is listed:
ttyS0Save and close the file. Now, you can reboot the server for testing purpose.
How Do I Connect Using a Serial Console?
You need to use the minicom command, which is a communication program that runs under most unices. You can install minicom as follows on your Debian / Ubuntu desktop system:# apt-get install minicom
For rpm based distro such as RHEL / Fedora / CentOS Linux, enter:
# yum install minicom
Run minicom as follows to create a configuration file:
# minicom -s -c on
Press [down] key and select Serial port setup:
- Press A to setup serial device name such as /dev/ttyS0
- Press E to setup Bps/Par/Bits (baud rate)
- Press [ESC] to exit
- From menu select "Save setup as DFL"
- Exit
# cat /etc/minicom/minirc.dfl
pu port /dev/ttyS0
pu baudrate 19200
pu bits 8
pu parity N
pu stopbits 1
pu rtscts No
Save and close the file. To connect to a serial console simply type the minicom command as follows:
# minicom
Sample outputs:
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