The Sheevaplug is a small ARM based “plug computer” manufactured by GlobalScale. This post explains how to connect over the serial connection for out-of-band access. A bit like connecting to the server processor of a unix server, or the alom/ilom of a Sun/Oracle box, or the Vsphere console of a vmware system.

Connect a USB cable from your PC to the sheevaplug’s micro USB port (also called the “JTAG” port) and proceed as below.

Load the driver:

$ sudo modprobe ftdi_sio vendor=0x9e88 product=0x9e8f

That should create a device called /dev/ttyUSB0 or /dev/ttyUSB1.

Use cu (call up) to make the serial connection. If you need to install it, it is part of the uucp package.

bash-4.2$ sudo yum whatprovides cu
[sudo] password for fred:
Loaded plugins: langpacks, presto
uucp-1.07-32.fc18.x86_64 : A set of utilities for operations between systems
Repo        : fedora
Matched from:
Filename    : /usr/bin/cu

(Okay so this is Fedora 18, not actually Red Hat). Install uucp:

# yum install uucp

Now try the connection:

bash-4.2$ cu -s 115200 -l /dev/ttyUSB0
cu: /dev/ttyUSB0: Line in use

bash-4.2$ sudo cu -s 115200 -l /dev/ttyUSB0
cu: /dev/ttyUSB0: Line in use

Line in use ? Even as root ? That’s a bug with uucp 1.07-3. What cu really wants is group write permission on the device. Give cu what it wants:

bash-4.2$ ls -l /dev/ttyU*
crw-rw---- 1 root dialout 188, 0 Feb 24 22:58 /dev/ttyUSB0
bash-4.2$ sudo chgrp root /dev/ttyUSB0
bash-4.2$ ls -l /dev/ttyU*
crw-rw---- 1 root root 188, 0 Feb 24 22:58 /dev/ttyUSB0

Now re-try the connection. I have noticed garbage characters, but they disappear if you press return a few times and wait 30 seconds or so.

bash-4.2$ sudo cu -s 115200 -l /dev/ttyUSB0
Connected.
�������'��Ѝ�����fw���:7���������q�8���:����������'��Ѝ�������fw���:7���������q�8���:�����fw���z���W��8'��XP^n��G��#
Debian GNU/Linux 6.0 debian ttyS0

debian login:
Password:

Job done. When your session is done, use ~. (tilde dot) to escape.