add example with real hardware
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Daniel Barlow
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129
doc/new.rst
129
doc/new.rst
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@ -129,6 +129,135 @@ Congratulations! You have installed your first Liminix system - albeit
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it has no practical use and it's not even real. The next step is to try
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running it on hardware.
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Installing on hardware
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**********************
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For the next example, we're going to install onto an actual hardware
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device. These steps have been tested using a GL-iNet GL-MT300A, which
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has been chosen for the purpose because it's cheap and easy to
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unbrick. Using some other Liminix-supported MIPS hardware device also
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*ought* to work here, but you accept the slightly greater bricking
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risk if it doesn't.
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You may want to acquire a `USB TTL serial cable
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<https://cpc.farnell.com/ftdi/ttl-232r-rpi/cable-debug-ttl-232-usb-rpi/dp/SC12825?st=usb%20to%20uart%20cable>`_
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when you start working with Liminix on real hardware. You
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won't *need* it for this example, assuming it works, but it
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allows you
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to see the boot monitor and kernel messages, and to login directly to
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the device if for some reason it doesn't bring its network up. You have options
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here: the FTDI-based cables are the Rolls Royce of serial cables,
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whereas the ones based on PL2303 and CP2102 chipsets are cheaper but
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also fussier - or you could even get creative and use e.g. a
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`Raspberry Pi <https://pinout.xyz/#>`_ or other SBC with a UART and
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TX/RX/GND header pins. Make sure that the voltages are compatible:
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this is a 3.3v device and you don't want to be sending it 5v or (even
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worse) 12v.
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Now we can build Liminix. Although we could use the same example
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configuration as we did for Qemu, you might not want to plug a DHCP
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server into your working LAN because it will compete with the real
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DHCP service. So we're going to use a different configuration with a
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DHCP client: this is :file:`examples/hello-from-mt300.nix`
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It's instructive to compare the two configurations:
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.. code-block:: console
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diff -u examples/hello-from-qemu.nix examples/hello-from-mt300.nix
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You'll see a new ``boot.tftp`` stanza which you can ignore,
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``services.dns`` has been removed, and the static IP address allocation
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has been replaced by a ``dhcp.client`` service.
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.. code-block:: console
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nix-build -I liminix-config=./examples/hello-from-mt300.nix \
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--arg device "import ./devices/gl-mt300a" -A outputs.default
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.. tip:: The first time you run this it may take several hours.
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Again? Yes, even if you ran the previous example. Qemu is
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set up as a big-endian system whereas the MediaTek SoC
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on this device is little-endian - so it requires building
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all of the dependencies including an entirely different
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MIPS gcc and library toolchain to the other one.
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This time in :file:`result/` you will see a bunch of files. Most of
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them you can ignore for the moment, but :file:`result/firmware.bin` is
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the firmware image you can flash.
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Flashing
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========
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Again, there are a number of different ways you could do this: using
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TFTP with a serial cable, through the stock firmware's web UI, or
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using the `vendor's "debrick" process
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<https://docs.gl-inet.com/router/en/3/tutorials/debrick/>`_. The last
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of these options has a lot to recommend it for a first attempt:
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* it works no matter what firmware is currently installed
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* it doesn't require plugging a router into the same network as your
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build system and potentially messing up your actual upstream
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* no need to open the device and add cables
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You can read detailed instructions on the vendor site, but the short version is:
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1. turn the device off
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2. connect it by ethernet cable to a computer
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3. configure the computer to have static ip address 192.168.1.10
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4. while holding down the Reset button, turn the device on
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5. after about five seconds you can release the Reset button
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6. visit http://192.168.1.1/ using a web browser on the connected computer
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7. click on "Browse" and choose :file:`result/firmware.bin`
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8. click on "Update firmware"
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9. wait a minute or so while it updates.
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There's no feedback from the web interface when the flashing is
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finished, but what should happen is that the router reboots and
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starts running Liminix. Now you need to figure out what address it got
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from DHCP - e.g. by checking the DHCP server logs, or maybe by pinging
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``hello.lan`` or something. Once you've found it on the
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network you can ping it and ssh to it just like you did the Qemu
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example, but this time for real.
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.. warning:: Do not leave the default root password in place on any
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device exposed to the internet! Although it has no
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writable storage and no default route, a motivated attacker
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with some imagination could probably still do something
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awful using it.
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Congratulations Part II! You have installed your first Liminix system on
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actual hardware - albeit that it *still* has no practical use.
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Exercise for the reader: change the default password by editing
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:file:`examples/hello-from-mt300.nix`, and then create and upload a
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new image that has it set to something less hopeless.
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Final thoughts
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**************
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* These are demonstration configs for pedagogical purposes. If you'd
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like to see some more realistic uses of Liminix,
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:file:`examples/rotuer,arhcive,extneder.nix` are based on some
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actual real hosts in my home network.
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* These example images are not writable. Later we will explain how to
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generate an image that can be changed after installation, and
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even use :command:`liminix-rebuild` (analogous to :command:`nixos-rebuild`)
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to keep it up to date.
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* The technique used here for flashing was chosen mostly because it
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doesn't need much infrastructure/tooling, but it is a bit of a faff
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(requires physical access, vendor specific). There are slicker ways
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to do it that need a bit more setup - we'll talk about that later as
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well.
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- using modules
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43
examples/hello-from-mt300.nix
Normal file
43
examples/hello-from-mt300.nix
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@ -0,0 +1,43 @@
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{ config, pkgs, lib, ... } :
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let
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inherit (pkgs) serviceFns;
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svc = config.system.service;
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in rec {
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imports = [
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../modules/network
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../modules/ssh
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../modules/vlan
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../modules/flashimage.nix
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];
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boot.tftp = {
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# IP addresses to use in the boot monitor when flashing/ booting
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# over TFTP. If you are flashing using the stock firmware's Web UI
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# then these dummy values are fine
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ipaddr = "192.0.2.115"; # my address
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serverip = "192.0.2.5"; # build machine or other tftp server
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};
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hostname = "hello";
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services.dhcpc = svc.network.dhcp.client.build {
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interface = config.hardware.networkInterfaces.lan;
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# don't start DHCP until the hostname is configured,
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# so it can identify itself to the DHCP server
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dependencies = [ config.services.hostname ];
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};
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services.sshd = svc.ssh.build { };
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users.root = {
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# the password is "secret". Use mkpasswd -m sha512crypt to
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# create this hashed password string
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passwd = "$6$y7WZ5hM6l5nriLmo$5AJlmzQZ6WA.7uBC7S8L4o19ESR28Dg25v64/vDvvCN01Ms9QoHeGByj8lGlJ4/b.dbwR9Hq2KXurSnLigt1W1";
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};
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defaultProfile.packages = with pkgs; [
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figlet
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];
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}
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