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====== Linksys NSLU2 ======

===== Web references =====

  * [[http://1wt.eu/articles/nslu2/|Hacking into the Linksys NSLU2]]
  * [[http://www.nslu2-linux.org/wiki/Debian/HomePage|Debian/NSLU2]]
  * [[http://www.nslu2-linux.org/wiki/Debian/BuildImage|How to build a new Debian/NSLU2 image]]

===== Hardware =====

See the [[wp>NSLU2]].

^ CPU    | XScale-IXP42x 266 MHz  |
^ RAM    | 32 Mb  |
^ Flash  | 8 Mb  |

===== Flashing a new firmware =====

Obviously we want Debian GNU/Linux on it!

==== Flashing a Debian kernel and initramfs ====

See [[http://www.cyrius.com/debian/nslu2/install.html|Installing Debian on the Linksys NSLU2]]

Put the NSLU2 in upgrade mode, as described into the **[[http://www.cyrius.com/debian/nslu2/install.html|HOWTO]]**. Then run the following commands:

<code>
apt-get install upslug2 slugimage
wget http://cyrius.com/debian/nslu2/files/sda1-2.6.18.dfsg.1-13etch2
upslug2 -i sda1-2.6.18.dfsg.1-13etch2
</code>

:-( The above is an **official Debian image**, for a system installed onto **/dev/sda1**. Unfortunately it **does not support** the integrated Ethernet interface (Intel IXP4xx) because it needs a proprietary microcode to operate.

After flashing the firmware, we can **prepare a Debian base system on and USB memory stick**. I prepared a 2 Gb USB stick following this **[[http://www.cyrius.com/debian/nslu2/unpack.html|Manual install]]**.

==== Flashing a Debian Installer ====

There is also an **unofficial Debian installer NSLU image** that can be found here: **[[http://www.slug-firmware.net/d-dls.php|www.slug-firmware.net]]**. This image contains a Debian installer that let you to start a standard installation. It contains also the microcode for the Ethernet port.

After flashing the Debian installer image you can login into the NSLU2 via ssh (login/password: **installer**/**install**):

<code>
ssh installer@192.168.1.77
</code>







==== Files ====

^ File  ^ Note  ^ Md5sum ^
^ {{.nslu2:debian-5.0beta1.zip}} [[http://www.slug-firmware.net/d-dls.php|web]]  | Unofficial Debian installer based on Debian Lenny  | d1101168a492f62810234b067724d3df  |
^ {{.nslu2:debian-4.0r3.zip}} [[http://www.slug-firmware.net/d-dls.php|web]]  | Unofficial Debian installer based on Debian 4.0 Etch  | b8b9fe6389b04cf8520157010b1a0a8f  |
^ {{.nslu2:sda1-2.6.18.dfsg.1-13etch2.bz2}} [[http://cyrius.com/debian/nslu2/files/sda1-2.6.18.dfsg.1-13etch2|web]]  | Firmware for root on /dev/sda1  | 53566d5b06418128255d50cd8226f8be  |


**Note:** I tried to install the Debian system on a 2Gb USB stick. I got problems using the debian-5.0beta1 installer: the system crashed several times at different stages of progress, so I was unable to complete it. I experienced some trouble also with the debian-4.0r3 installer: the program insists on crashing during partition format, so I pre-formatted the USB  stick. During setup I loaded these modules:

  * ext3-modules-2.6.18-6-ixp4xx-di
  * partman-ext3
  * usb-storage-modules-2.6.18-6-ixp4xx-di

===== Problem with halt and reboot =====

If you boot the NSLU2 with the serial line connected to an host (I use minicom to debug the boot process), then you will find that **''reboot''** or **''halt''** commands will be ignored.

I did not investigate much, just discovered that **''/etc/init.d/rc {0|6}''** works.


===== Serial port pinout =====

^ Pin 1	| 3.3V (pin 1 has a white stripe next to it)   |
^ Pin 2	| RXD (from serial terminal program to NSLU2)  |
^ Pin 3	| TXD (from NSLU2 to serial terminal program)  |
^ Pin 4	| GND  |

By default, RedBoot, APEX and the Linux kernel all use **115200,8,N,1** settings.

===== Customize the Debian Firmware =====

Install the **slugimage** package, download the [[http://cyrius.com/debian/nslu2/files/sda1-2.6.18.dfsg.1-13etch2|original image]] and unpack it:

<code>
slugimage --unpack --input sda1-2.6.18.dfsg.1-13etch2
</code>

Several files will be extracted:

  * **apex.bin**: second stage boot loader for ARM chip (little-endian image)
  * **ramdisk.gz**: initramfs image (little-endian, gzip, cpio archive)
  * **RedBoot**: RedBoot boot manager
  * **SysConf**: Configuration of the NSLU2
  * **Trailer**: Trailer
  * **vmlinuz**: kernel image (little-endian image)

I changed the kernel image **vmlinuz** and the init ramdisk **ramdisk.gz** with customized versions

Note that the extracted files are little-endian, where the images provided by me are big-endian, so I byte-swapped them before packing back. Also note that the initramfs image **must be padded to 4 Mb** size.

<code>
dd if=ramdisk.gz of=ramdisk-pad.gz ibs=4M conv=sync
byteswap.py vmlinuz vmlinuz-swap
byteswap.py ramdisk-pad.gz ramdisk-pad.gz-swap
slugimage --pack --output myfirmware-2.6.18-5-ixp4xx-1.bin -k vmlinuz-swap -r ramdisk-pad.gz-swap -L apex.bin
</code>

Do not use the **''%%--little%%''** option of ''slugimage'' to byte-swap kernel and initramfs images, because it swaps also the ''apex.bin'' file.

Here it is the **byteswap.py** Python utility I used to byte-swap the files:

<code python>
#!/usr/bin/python
# swap every 32bit word in input and write it to output

import array, sys

if len(sys.argv) != 3:
  sys.stderr.write('Invalid arguments.\n')
  sys.stderr.write('Usage: %s <input> <output>\n' % sys.argv[0])
  sys.exit(1)

if sys.argv[1] == '-':
  file = sys.stdin
else:
  file = open(sys.argv[1], 'rb')

input = file.read()
a = array.array('I')
# add padding if needed
a.fromstring(input + '\0' * (4-len(input)&3))
a.byteswap()

if sys.argv[2] == '-':
  file = sys.stdout
else:
  file = open(sys.argv[2], 'wb')

a.tofile(file)
</code>

===== Always-On =====

{{  :doc:appunti:hardware:nslu2:nslu2_always-on_patch.jpg?200|NSLU2 Always-on patch}}
The NSLU2 does not support the Always-On natively, there are several recipes to implement this feature, I choosed a simple one (a simple wire) from [[http://www.nslu2-linux.org/wiki/HowTo/ForcePowerAlwaysOn|this page]].

^ power restore  | The NSLU2 power-on an boot as soon as the power is restored.  |
^ power button   | When the power button is pressed: The system is going down for reboot NOW!  |
^ reboot(8)      | The NSLU2 properly reboots.  |
^ poweroff(8)    | The shutdown sequence is run, but power is not removed and LEDs stay on. You can restart by pressing the power button.  |