Link to an installing tutorial. I just need that.

From what I've read I understand that Linux can be started from within TI OS.

Yup

My first question is this...it's possibile to erase completely the built-in OS and replace it with Linux?

With the recently released nLaunch and nLaunch CX, one can indeed launch Linux directly from the boot2, without having to carry TI's heavyweight OS. The latest versions are 10+MB, which is huge on the older Clickpad & Touchpad models, which have only 32 MB of NAND flash in total, and some of those are used by the boot2 + diags + filesystem data.

The same Debian could be installed in the internal memory without using a USB stick?

Nope, Nspire calculators use a proprietary filesystem for which Linux has no open source drivers - and anyway, the internal memory is too small. Even the best-equipped Nspire models of the CX series have only 128 MB of NAND Flash.

One last question. My intention of installing linux is connected to my intention of porting a python interpreter on the NSPIRE. For what I understand, the CPython implementation should be pure C...so what kind of problems have till now prevented this porting?

* the sheer weight of CPython + libs: multiple megabytes are a severe toll on a platform with less than 32 MB of usable Flash memory;
* the predictable slowness of Python (all the more it's not the most efficient interpreted, dynamic language...) on an ARM9 CPU which cannot be overclocked above ~222 MHz on some machines (some others leave a bit more headroom);
* the likely incompleteness of TI's OS wrt. POSIX APIs (TI's OS being based on proprietary Nucleus RTOS), and the incompleteness of the Ndless syscalls + libraries (even when complemented by e.g. newlib).

Lionel, thanks for your prompt answers. You say

Nspire calculators use a proprietary filesystem for which Linux has no open source drivers - and anyway, the internal memory is too small.

So I understand that Debian was booted from a USB drive. How can this be done? I mean...I suppose there is no "boot from usb" as there is on the PC BIOS...how can you boot from an external device? Do you need first a working linux in the NSPIRE and then mount the external drive and chroot there?

Thanks again for the help

Tiziano

If your usb drive is working with linux already, you only have to remove "root=/dev/ram" in your bootscript and replace it with "root=/dev/sda" or "root=/dev/sda1", depends on whether you are using partitions.
You should remove the "initrd" line, too. It doesn't do anything but increasing the boot time.

You won't be able to use wifi without a proper self-powered usb hub.
Keyboard would work, but only when linux is running.
I think you want to use it in "calculator mode" (when TI's OS is running), which won't work (for now)

one of the users gave me this website http://tiplanet.org/nspire-linux-builds/ but i have no idea how to use it

You have to use your mouse and move it so the cursor is over a blue text "link" on which you can click (press left mouse button) xD

You just have to create a directory "linux" on your calc and copy
-zImage.tns
-linuxloader2.tns
-initrd.tns
-start_initrd.ll2.tns into it.
You also need to copy ndless.cfg.tns into "ndless". You can find all of these on nspire-linux-builds.
After that, it should already work by launching start_initrd.ll2.

Which .zip file? We don't have any zips there!
The tiny image should be enough for you. For the other ones you'll need to boot from an usb drive (which is a bit complicated)