How to activate Serial over LAN

From this article, you will learn about Serial over LAN and how to activate it.

Serial Over LAN (SOL) is a mechanism that enables the input and output of the serial port of a managed system to be redirected over IP. This is done through IPMI.

Activating serial over LAN

In order to activate SOL (serial over LAN), enter the following command:

ipmitool -C 3 -I lanplus -H <ipaddr> -U <user> -P <pass> sol activate

Using cipher suite 3 is essential (if that is not the default) because communication via LANplus is not possible otherwise.

If the following error message appears, you need to activate SOL for the user:

$ ipmitool -C 3 -I lanplus -H <ipaddr> -U <user> -P <pass> sol activate
Info: SOL payload disabled

$ ipmitool -C 3 -I lanplus -H <ipaddr> -U <user> -P <pass> sol payload enable <channel> <user-id>

After that, you can see the BIOS output. Accessing the boot loader and/or the booted system requires additional settings.

GRUB2

For GRUB2, simply change some lines to match the following in /etc/default/grub and re-generate the settings.

With the Supermicro X9SRi-F, the serial console is on ttyS2/unit=2. With the Asus Z10PA-U8, it is on ttyS1/unit=1. And with the Intel S1200V3RPL, it is on ttyS0/unit=0. It should also be noted that the Baud rate needs to be set at 57600 with the Asus Z10PA-U8, and 115200 with all others.

Intel S1200V3RPL

GRUB_CMDLINE_LINUX_DEFAULT="nomodeset console=tty0 console=ttyS0,115200n8"
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

Supermicro X9SRi-F

GRUB_CMDLINE_LINUX_DEFAULT="nomodeset console=tty0 console=ttyS2,115200n8"
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=2 --word=8 --parity=no --stop=1"

Asus Z10PA-U8

GRUB_CMDLINE_LINUX_DEFAULT="nomodeset console=tty0 console=ttyS1,57600n8"
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=57600 --unit=1 --word=8 --parity=no --stop=1"

GRUB (grub-legacy)

For GRUB1 (grub-legacy), add the following lines to /boot/grub/menu.lst or /boot/grub/grub.conf (CentOS):

Intel S1200V3RPL

serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=5 serial console

Supermicro X9SRi-F

serial --unit=2 --speed=57600 --word=8 --parity=no --stop=1
terminal --timeout=5 serial console

Asus Z10PA-U8

serial --unit=1 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=5 serial console

At the same time, you need to add the same serial port needs to the boot options of the kernel. That is ttyS0 with the Intel S1200V3RPL, ttyS1 with the Asus Z10PA-U8, and ttyS2 with the Supermicro X9SRi-F.

console=tty0 console=ttyS0,115200n8

This tells the kernel to output information on the first serial port. Changing GRUB_TERMINAL to serial means any input/output is redirected to the serial port. A local screen will not display a boot menu anymore, and thus, it is no longer possible selecting a boot entry via KVM Console or KVM. After a reboot, the output will be sent in parallel to both the local screen and the serial port.

After that, you need to set up a terminal for the serial port in your system. Debian 7.x (wheezy) / Debian 8 with Sys-V Init

You need to add the following line to /etc/inittab. Here again, use ttyS0 and 115200 Baud with the Intel S1200V3RPL, ttyS2 and 115200 Baud with the Supermicro X9SRi-F, and ttyS1 and 57600 Baud with the Asus Z10PA-U8:

T0:2345:respawn:/sbin/getty -L ttyS0 115200 vt100

After that, you can activate the terminal by entering init q.

Ubuntu (up until 14.10 with Upstart)

Create the file /etc/init/ttyS0.conf with the following content (or alternatively, ttyS2.conf with ttyS2 and 115200 Baud with the Supermicro X9SRi-F models, or ttyS1.conf with ttyS1 and 57600 Baud with the Asus Z10PA-U8 models):

# ttyS0 - getty
#
# This service maintains a getty on ttyS0 from the point the system is
# started until it is shut down again.

start on stopped rc RUNLEVEL=[2345]
stop on runlevel [!2345]

respawn
exec /sbin/getty -L ttyS0 115200 vt100

After that, you can activate the terminal by entering start ttyS0.

CentOS

In CentOS 6.x, the configuration is similar to Ubuntu. However, /etc/init/serial.conf automatically starts a getty on the serial port, which adds the port /etc/securetty. So you just need to configure the serial console in grub.conf and attach the appropriate kernel option.

Debian 8 / OpenSuSE / Fedora

For Debian 8 (jessie), OpenSuSE, and other distributions such as Fedora which use systemd and GRUB2, just change /etc/default/grub accordingly and renew the configuration using grub2-mkconfig. At the next boot, systemd will automatically start using the serial port of GRUB2.

Serial Console

Now, you will see a login quickly if you connect via ipmitool:

 $ ipmitool -C 3 -I lanplus -H <ipaddr> -U <user> -P <pass> sol activate
 [SOL Session operational.  Use ~? for help]

 Debian GNU/Linux 7 Debian-70-wheezy-64-minimal ttyS0

 Debian-70-wheezy-64-minimal login: