Tiny Linux Plug Computers: Wall Wart Linux Servers - page 2
Choosing the Right One
Your first plug computer just arrived and you've unpacked it. What now?
Ideally, you could plug in a network cable, power the device on, let it get a network address and ssh into it. But with most models it's not quite that simple. The default configuration may not configure the network automatically -- in which case you'll need a serial cable.
The serial connection should plug into your desktop's USB port and should create a device with a name like /dev/ttyUSB0. Check for it:
$ ls -l /dev/ttyUSB* crw-rw---- 1 root dialout 188, 0 2011-01-22 21:02 /dev/ttyUSB0
Notice that on my Ubuntu machine, the device is writable by anyone in the dialout group. So I added myself to that group -- I had to log out and back in for the change to take effect. Of course you can run sudo chmod a+rw /dev/ttyUSB0 as a temporary fix.
Once you have read and write permission on the tty device, you can connect to it with a terminal program like minicom; but I find it easiest to use GNU screen and specify the speed:
$ screen /dev/ttyUSB0 115200
Now you're talking to the plug. If you don't see boot messages flying by, hit return:
Debian GNU/Linux 5.0 debian ttyS0 debian login:
Log in as root. The password varies by manufacturer; with any luck your plug came with documentation, but if not, common passwords are nosoup4u (Globalscale), root (Ionics) and stxadmin (Dockstar).
You'll find yourself in a Busybox shell, with limited versions of most of the standard Linux commands like ls, mv, less, ps, kill, grep and even vi.
Explore! Configure the network interfaces with the standard Linux tools ifconfig, iwconfig and so forth. You can write scripts in sh, Python or Perl. /etc/init.d and /etc/rc.local work like you expect, and you can even apt-get install new packages.
Have fun, and stay tuned for the next article, in which I'll cover details like troubleshooting and how to use the uBoot boot loader.