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Developer Manual
################
As a developer working on Liminix, or implementing a service or
module, you probably want to test your changes more conveniently
than by building and flashing a new image every time. This manual
documents various affordances for iteration and experiments.
In general, packages and tools that run on the "build" machine are
available in the ``buildEnv`` derivation and can most easily
be added to your environment by running :command:`nix-shell`
Emulated devices
****************
Liminix has a ``qemu`` device, which generates images suitable for
running on your build machine using the free `QEMU machine emulator <http://www.qemu.org>`_.
This is useful for developing userland without needing to keep
flashing or messing with U-Boot: it also enables testing against
emulated network peers using `QEMU socket networking <https://wiki.qemu.org/Documentation/Networking#Socket>`_,
which may be preferable to letting Liminix loose on your actual LAN.
To build it,
.. code-block:: console
nix-build -I liminix-config=path/to/your/configuration.nix --arg device "import ./devices/qemu" -A outputs.default
In a ``buildEnv`` nix-shell, you can use the :command:`mips-vm` command
to run Qemu with appropriate options. It connects the Liminix
serial console and the `QEMU monitor <https://www.qemu.org/docs/master/system/monitor.html>`_ to stdin/stdout. Use ^P (not ^A) to switch to the monitor.
.. code-block:: console
nix-shell --run "mips-vm result/vmlinux result/squashfs"
If you run with ``--background /path/to/some/directory`` as the first
parameter, it will fork into the background and open Unix sockets in
that directory for console and monitor. Use :command:`connect-vm`
(also in the ``buildEnv`` environment) to connect to either of these
sockets, and ^O to disconnect.
Networking
==========
VMs can network with each other using QEMU
socket networking. We observe these conventions, so that we can run
multiple emulated instances and have them wired up to each other in
the right way:
* multicast 230.0.0.1:1234 : access (interconnect between router and "isp")
* multicast 230.0.0.1:1235 : lan
* multicast 230.0.0.1:1236 : world (the internet)
A VM started with :command:`mips-vm` is connected to "lan" and "access", and
the emulated border network gateway (see below) runs PPPoE and is
connected to "access" and "world".
Border Network Gateway
----------------------
In pkgs/routeros there is a derivation to install and configure
`Mikrotik RouterOS <https://mikrotik.com/software>`_ as a PPPoE access
concentrator connected to the ``access`` and ``world`` networks, so that
Liminix PPPoE client support can be tested without actual hardware.
This is made available as the :command:`routeros` command in
``buildEnv``, so you can do something like::
mkdir ros-sockets
nix-shell
nix-shell$ routeros ros-sockets
nix-shell$ connect-vm ./ros-sockets/console
to start it and connect to it. Note that by default it runs in the
background. It is connected to "access" and "world" virtual networks
and runs a PPPoE service on "access" - so a Liminix VM with a
PPPOE client can connect to it and thus reach the virtual internet.
[ check, but pretty sure this is not the actual internet ]
`Liminix does not provide RouterOS licences and it is your own
responsibility if you use this to ensure you're compliant with the
terms of Mikrotik's licencing. It may be supplemented or replaced in
time with configurations for RP-PPPoE and/or Accel PPP.`
Hardware devices
****************
How you get your image onto hardware will vary according to the
device, but is likely to involve taking it apart to add wires to
serial console pads/headers, then using U-Boot to fetch images over
TFTP. The OpenWrt documentation has a `good explanation <https://openwrt.org/docs/techref/hardware/port.serial>`_ of what you may expect to find on
the device.
There is a rudimentary TFTP server bundled with the system which runs
from the command line, has an allowlist for client connections, and
follows symlinks, so you can have your device download images direct
from the :file:`./result` directory without exposing :file:`/nix/store/` to the
internet or mucking about copying files to :file:`/tftproot`. If the
permitted device is to be given the IP address 192.168.8.251 you might
do something like this:
.. code-block:: console
nix-shell --run "tufted -a 192.168.8.251 result"
Now add the device and server IP addresses to your configuration:
.. code-block:: nix
boot.tftp = {
serverip = "192.168.8.111";
ipaddr = "192.168.8.251";
};
and then build the derivation for ``outputs.default`` or
``outputs.flashimage`` (for which it will be an alias on any device
where this is applicable). You should find it has created
* :file:`result/firmware.bin` which is the file you are going to flash
* :file:`result/flash.scr` which is a set of instructions to U-Boot to
download the image and write it to flash after erasing the appropriate
flash partition.
.. NOTE::
TTL serial connections typically have no form of flow control and
so don't always like having massive chunks of text pasted into
them - and U-Boot may drop characters while it's busy. So don't
necessarily expect to copy-paste the whole of :file:`boot.scr` into
a terminal emulator and have it work just like that. You may need
to paste each line one at a time, or even retype it.
For a faster edit-compile-test cycle, you can build a TFTP-bootable
image instead of flashing. In your device configuration add
.. code-block:: nix
imports = [
./modules/tftpboot.nix
];
and then build ``outputs.tftpboot``. This creates a file in
``result/`` called ``boot.scr``, which you can copy and paste into
U-Boot to transfer the kernel and filesystem over TFTP and boot the
kernel from RAM.
Networking
==========
You probably don't want to be testing a device that might serve DHCP,
DNS and routing protocols on the same LAN as you (or your colleagues,
employees, or family) are using for anything else, because it will
interfere. You also might want to test the device against an
"upstream" connection without having to unplug your regular home
router from the internet so you can borrow the cable/fibre/DSL.
``bordervm`` is included for this purpose. You will need
* a Linux machine with a spare (PCI or USB) ethernet device which you can dedicate to Liminix
* an L2TP service such as https://www.aa.net.uk/broadband/l2tp-service/
You need to "hide" the Ethernet device from the host - for PCI this
means configuring it for VFIO passthru; for USB you need to unload the
module(s) it uses. I have this segment in configuration.nix which you
may be able to adapt:
.. code-block:: nix
boot = {
kernelParams = [ "intel_iommu=on" ];
kernelModules = [
"kvm-intel" "vfio_virqfd" "vfio_pci" "vfio_iommu_type1" "vfio"
];
postBootCommands = ''
# modprobe -i vfio-pci
# echo vfio-pci > /sys/bus/pci/devices/0000:01:00.0/driver_override
'';
blacklistedKernelModules = [
"r8153_ecm" "cdc_ether"
];
};
services.udev.extraRules = ''
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="8153", OWNER="dan"
'';
Then
you can execute :command:`run-border-vm` in a ``buildEnv`` shell,
which starts up QEMU using the NixOS configuration in
:file:`bordervm-configuration.nix`.
In this VM
* your Liminix checkout is mounted under :file:`/home/liminix/liminix`
* TFTP is listening on the ethernet device and serving
:file:`/home/liminix/liminix`. The server IP address is 10.0.0.1
* a PPPOE-L2TP relay is running on the same ethernet card. When the
connected Liminix device makes PPPoE requests, the relay spawns
L2TPv2 Access Concentrator sessions to your specified L2TP LNS.
Note that authentication is expected at the PPP layer not the L2TP
layer, so the PAP/CHAP credentials provided by your L2TP service can
be configured into your test device - bordervm doesn't need to know
about them.
To configure bordervm, you need a file called :file:`bordervm.conf.nix`
which you can create by copying and appropriately editing :file:`bordervm.conf-example.nix`
.. note::
If you make changes to the bordervm configuration after executing
:command:`run-border-vm`, you need to remove the :file:`border.qcow2` disk
image file otherwise the changes won't get picked up.
Running tests
*************
You can run all of the tests by evaluating :file:`ci.nix`, which is the
input I use in Hydra. Note that it expects Nixpkgs stable `and` unstable
as inputs, because it builds the qemu device against both.
.. code-block:: console
nix-build --argstr liminix `pwd` --arg nixpkgs "<nixpkgs>" \
--argstr unstable `pwd`/../unstable-nixpkgs/ ci.nix
To run a single named test, use the ``-A`` flag. For example, ``-A pppoe``
Troubleshooting
***************
Diagnosing unexpectedly large images
====================================
Sometimes you can add a package and it causes the image size to balloon
because it has dependencies on other things you didn't know about. Build the
``outputs.manifest`` attribute, which is a JSON representation of the
filesystem, and you can run :command:`nix-store --query` on it.
.. code-block:: console
nix-build -I liminix-config=path/to/your/configuration.nix \
--arg device "import ./devices/qemu" -A outputs.manifest \
-o manifest
nix-store -q --tree manifest
Contributing
************
Contributions are welcome, though in these early days there may be a
bit of back and forth involved before patches are merged:
Please get in touch somehow `before` you invest a lot of time into a
code contribution I haven't asked for. Just so I know it's expected
and you're not wasting time doing something I won't accept or have
already started on.
Nix language style
==================
This section describes some Nix language style points that we
attempt to adhere to in this repo.
* favour ``callPackage`` over raw ``import`` for calling derivations
or any function that may generate one - any code that might need
``pkgs`` or parts of it.
* prefer ``let inherit (quark) up down strange charm`` over
``with quark``, in any context where the scope is more than a single
expression or there is more than one reference to ``up``, ``down``
etc. ``with pkgs; [ foo bar baz]`` is OK,
``with lib; stdenv.mkDerivation { ... }`` is usually not.
* ``<liminix>`` is defined only when running tests, so don't refer to it
in "application" code
* the parameters to a derivation are sorted alphabetically, except for
``lib``, ``stdenv`` and maybe other non-package "special cases"
* indentation is whatever emacs nix-mode says it is.
* where a ``let`` form defines multiple names, put a newline after the
token ``let``, and indent each name two characters
* to decide whether some code should be a package or a module?
Packages are self-contained - they live in ``/nix/store/eeeeeee-name``
and don't directly change system behaviour by their presence or
absense. modules can add to
``/etc`` or ``/bin`` or other global state, create services, all that
side-effecty stuff. Generally it should be a package unless it
can't be.
Copyright
=========
The Nix code in Liminix is MIT-licenced (same as Nixpkgs), but the
code it combines from other places (e.g. Linux, OpenWrt) may have a
variety of licences. I have no intention of asking for copyright
assignment: just like when submitting to the Linux kernel you retain
the copyright on the code you contribute.
Code of Conduct
===============
Please govern yourself in Liminix project venues according to the
`Code of Conduct <https://gti.telent.net/dan/liminix/src/commit/7bcf6b15c3fdddafeda13f65b3cd4a422dc52cd3/CODE-OF-CONDUCT.md>`_
Where to send patches
=====================
Liminix' primary repo is https://gti.telent.net/dan/liminix but you
can't send code there directly because it doesn't have open registrations.
* There's a `mirror on Github <https://github.com/telent/liminix>`_ for
convenience and visibility: you can open PRs against that
* or, you can send me your patch by email using `git send-email <https://git-send-email.io/>`_
* or in the future, some day, we will have federated Gitea using
ActivityPub.

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The Future
##########
What about NixWRT?
This is an in-progress rewrite of NixWRT, incorporating Lessons
Learned. That said, as of today it is not yet at feature parity.
Liminix will eventually provide these differentiators over NixWRT:
* a writable filesystem so that software updates or reconfiguration
(e.g. changing passwords) don't require taking the device offline to
reflash it.
* more flexible service management with dependencies, to allow
configurations such as "route through PPPoE if it is healthy, with
fallback to LTE"
* a spec for valid configuration options (a la NixOS module options)
to that we can detect errors at evaluation time instead of producing
a bad image.
* a network-based mechanism for secrets management so that changes can
be pushed from a central location to several Liminix devices at once
* send device metrics and logs to a monitoring/alerting/o11y
infrastructure
Today though, it does approximately none of these things and certainly
not on real hardware.
Articles of interest
####################
* `Build Safety of Software in 28 Popular Home Routers <https://cyber-itl.org/assets/papers/2018/build_safety_of_software_in_28_popular_home_routers.pdf>`_: "of the access
points and routers we reviewed, not a single one took full
advantage of the basic application armoring features provided by
the operating system. Indeed, only one or two models even came
close, and no brand did well consistently across all models tested"
* `A PPPoE Implementation for Linux <https://static.usenix.org/publications/library/proceedings/als00/2000papers/papers/full_papers/skoll/skoll_html/index.html>`_:
"Many DSL service providers use PPPoE for residential broadband
Internet access. This paper briefly describes the PPPoE protocol,
presents strategies for implementing it under Linux and describes in
detail a user-space implementation of a PPPoE client."
* `PPP IPV6CP vs DHCPv6 at AAISP <https://www.revk.uk/2011/01/ppp-ipv6cp-vs-dhcpv6.html>`_
* `Creating a Home IPv6 Network (James Bottomley) <https://blog.hansenpartnership.com/creating-a-home-ipv6-network/>`_

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:maxdepth: 3 :maxdepth: 3
:caption: Contents: :caption: Contents:
intro new
user
developer
etc
Indices and tables Indices and tables

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Getting Started
###############
Liminix is very configurable, which can make it initially daunting
especially if you're learning Nix or Linux or networking concepts at
the same time. In this section we build some "worked example" Liminix
images to introduce the concepts. If you follow the examples exactly,
they should work. If you change things as you go along, they may work
differently or not at all, but the experience should be educational
either way.
.. warning:: The first example we will look at runs under emulation,
so there is no danger of bricking your hardware
device. For the second example you may (if you have
appropriate hardware and choose to do so) flash the
configuration onto an actual router. There is always a
risk of rendering the device unbootable when you do this,
and various ways to recover depending on what went wrong.
We'll write more about that at the appropriate point
Requirements
************
You will need a reasonably powerful computer running Nix. Devices
that run Liminix are unlikely tohave the CPU power and disk space to
be able to build it in situ, so the build process is based around
"cross-compilation" from another computer. The build machine can be
any reasonably powerful desktop/laptop/server PC running NixOS.
Standalone Nixpkgs installations on other Linux distribuions or MacOS
also ought to work (but I haven't tested that configuration)
Running in Qemu
***************
Clone the Liminix git repository and change into its directory
.. code-block:: console
git clone https://gti.telent.net/dan/liminix
cd liminix
Now build Liminix
.. code-block:: console
nix-build -I liminix-config=./examples/hellonet.nix \
--arg device "import ./devices/qemu" -A outputs.default
In this command ``liminix-config`` points to the configuration for the
device (services, users, filesystem, secrets) and ``device`` is the
file for your hardware device definition. ``outputs.default`` tells
Liminix to build the appropriate image output appropriate to
flash to the hardware device: for the qemu "hardware" it's an alias
for ``outputs.vmbuild``, which creates a directory containing a root
filesystem image and a kernel.
.. tip:: The first time you run this it may take several hours,
because it builds all of the dependencies including a full
MIPS gcc and library toolchain. Once those intermediate build
products are in the nix store, subsequent builds will be much
faster - practically instant, if nothing has changed.
Now you can try it:
.. code-block:: console
nix-shell --run "mips-vm ./result/vmlinux ./result/rootfs"
This starts the Qemu emulator to run the Liminix configuration you
just built. It connects the Liminix serial console and the `QEMU
monitor <https://www.qemu.org/docs/master/system/monitor.html>`_ to
stdin/stdout. Use ^P (not ^A) to switch to the monitor.
You should now see Linux boot messages and after a few seconds be
presented with a login prompt. You can login on the console as
``root`` (no password) and poke around to see what processes are
running. Run ``shutdown`` to shut it down cleanly, or press ^P then
type ``exit`` at the monitor to stop it suddenly.
To see that it running an ssh service we need to connect to its
emulated network. Start the machine again, if you had stopped it,
and open up a second terminal on your build machine. We're going to
run another virtual machine attached to the virtual network, which will
request an IP address from our Liminix system and give you a shell
you can run ssh from.
- using modules
- link to module reference
- creating custom services
- longrun or oneshot
- dependencies
- outputs
- creating your own modules
- hacking on Liminix itself
- contributing
- external links and resources
- module reference
- hardware device reference

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User Manual
###########
This manual is an early work in progress, not least because Liminix is
not yet really ready for users who are not also developers. Your
feedback to improve it is very welcome.
Installation
************
The Liminix installation process is not quite like installing NixOS on
a real computer, but some NixOS experience will nevertheless be
helpful in understanding it. The steps are as follows:
* Decide whether you want the device to be updatable in-place (there
are advantages and disadvantages), or if you are happy to generate
and flash a new image whenever changes are required.
* Create a :file:`configuration.nix` describing the system you want
* Build an image
* Flash it to the device
Supported devices
=================
For a list of devices that Liminix (present or previous versions)
has run on, refer to `devices/ in the source repo <https://gti.telent.net/dan/liminix/src/branch/main/devices>`_. For devices that _currently_ build,
cross-reference it with `the CI status <https://build.liminix.org/jobset/liminix/build#tabs-jobs>`_. Everything that builds is (usually) expected
to run, so if you end up with an image that builds but doesn't
boot, please report it as a bug.
As of June 2023 the device list is a little thin. Adding devices based
on the Atheros or Mediatek (Ralink) platform should be quite
straightforward if you have some C/Linux kernel experience and are
prepared to open it up and attach serial wires: please refer to the
Developer Manual.
Choosing a flavour (read-only or updatable)
===========================================
Liminix installations come in two "flavours"- read-only or in-place
updatable:
* a read-only installation can't be updated once it is flashed to your
device, and so must be reinstalled in its entirety every time you
want to change it. It uses the ``squashfs`` filesystem which has
very good compression ratios and so you can pack quite a lot of
useful stuff onto your device. This is good if you don't expect
to change it often.
* an updatable installation has a writable filesystem so that you can
update configuration, upgrade packages and install new packages over
the network after installation. This uses the `jffs2
<http://www.linux-mtd.infradead.org/doc/jffs2.html>`_ filesystem:
although it does compress the data, the need to support writes means
that it can't pack quite as small as squashfs, so you will not have
as much space to play with.
Updatability caveats
~~~~~~~~~~~~~~~~~~~~
At the time of writing this manual the read-only squashfs support is
much more mature. Consider also that it may not be possible to perform
"larger" updates in-place even if you do opt for updatability. If you
have (for example) an 11MB system on a 16MB device, you won't be able
to do an in-place update of something fundamental like the C library
(libc), as this will temporarily require 22MB to install all the
packages needing the new library before the packages using the old
library can be removed. A writable system will be more useful for
smaller updates such as installing a new package (perhaps you
temporarily need tcpdump to diagnose a network problem) or for
changing configuration files.
Note also that the kernel is not part of the filesystem so cannot be
updated this way. Kernel changes require a full reflash.
Creating configuration.nix
==========================
You need to create a :file:`configuration.nix` that describes your
device and the services that you want to run on it. The best way to
get started is by reading one of the examples such as
:file:`examples/rotuer.nix` and modifying it to your needs.
:file:`configuration.nix` conventionally describes the packages, services,
user accounts etc of the device. It does not describe the hardware
itself, which is specified separately in the build command (as you
will see below).
Most of the functionality of a Liminix system is driven by *services*
which are declared by *modules*: thus, to add for example an NTP service
you first add :file:`modules/ntp` to your ``imports`` list, then
you create a service by calling :code:`config.system.service.ntp.build { .... }`
with the appropriate service-dependent configuration parameters.
.. code-block:: nix
let svc = config.system.service;
in {
# ...
imports = [
./modules/ntp
# ....
];
config.services.ntp = svc.ntp.build {
pools = { "pool.ntp.org" = ["iburst"]; };
makestep = { threshold = 1.0; limit = 3; };
};
A :ref:`full list of module options <module-options>` is provided
later in this manual.
You *most likely* want to include the ``standard`` module unless you
have a quite unusual use case for a very minimal system, in which case
you will understand what it does and what happens if you leave it out.
.. code-block:: nix
imports = [
./modules/standard.nix
]
configuration.rootfsType = "jffs2"; # or "squashfs"
Building
========
Build Liminix using the :file:`default.nix` in the project toplevel
directory, passing it arguments for configuration and hardware. For
example:
.. code-block:: console
nix-build -I liminix-config=./tests/smoke/configuration.nix \
--arg device "import ./devices/qemu" -A outputs.default
In this command ``<liminix-config>`` points to your
:file:`configuration.nix`, ``device`` is the file for your hardware device
definition, and ``outputs.default`` will generate some kind of
Liminix image output appropriate to that device.
For the qemu device in this example, ``outputs.default`` is an alias
for ``outputs.vmbuild``, which creates a directory containing a
squashfs root image and a kernel. You can use the :command:`mips-vm` command to
run this.
For the currently supported hardware devices, ``outputs.default``
creates a directory containing a file called ``firmware.bin``. This
is a raw image file that can be written directly to the firmware flash
partition.
Flashing
========
Flashing from the boot monitor
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If you are prepared to open the device and have a TTL serial adaptor
of some kind to connect it to, you can probably flash it using U-Boot.
This is quite hardware-specific, and sometimes involves soldering:
please refer to the Developer Manual.
Flashing from an existing Liminix system with :command:`flashcp`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The flash procedure from an existing Liminix-system is two-step.
First we reboot the device (using "kexec") into an "ephemeral"
RAM-based version of the new configuration, then when we're happy it
works we can flash the image - and if it doesn't work we can reboot
the device again and it will boot from the old image.
Building the RAM-based image
............................
To create the ephemeral image, build ``outputs.kexecboot`` instead of
``outputs.default``. This generates a directory containing the root
filesystem image and kernel, along with an executable called `kexec`
and a `boot.sh` script that runs it with appropriate arguments.
For example
.. code-block:: console
nix-build --show-trace -I liminix-config=./examples/arhcive.nix \
--arg device "import ./devices/gl-ar750"
-A outputs.kexecboot && \
(tar chf - result | ssh root@the-device tar -C /run -xvf -)
and then login to the device and run
.. code-block:: console
cd /run/result
sh ./boot.sh .
This will load the new kernel and map the root filesystem into a RAM
disk, then start executing the new kernel. *This is effectively a
reboot - be sure to close all open files and finish anything else
you were doing first.*
If the new system crashes or is rebooted, then the device will revert
to the old configuration it finds in flash.
Building the second (permanent) image
.....................................
While running in the kexecboot system, you can copy the permanent
image to the device with :command:`ssh`
.. code-block:: console
build-machine$ tar chf - result/firmware.bin | \
ssh root@the-device tar -C /run -xvf -
Next you need to connect to the device and locate the "firmware"
partition, which you can do with a combination of :command:`dmesg`
output and the contents of :file:`/proc/mtd`
.. code-block:: console
<5>[ 0.469841] Creating 4 MTD partitions on "spi0.0":
<5>[ 0.474837] 0x000000000000-0x000000040000 : "u-boot"
<5>[ 0.480796] 0x000000040000-0x000000050000 : "u-boot-env"
<5>[ 0.487056] 0x000000050000-0x000000060000 : "art"
<5>[ 0.492753] 0x000000060000-0x000001000000 : "firmware"
# cat /proc/mtd
dev: size erasesize name
mtd0: 00040000 00001000 "u-boot"
mtd1: 00010000 00001000 "u-boot-env"
mtd2: 00010000 00001000 "art"
mtd3: 00fa0000 00001000 "firmware"
mtd4: 002a0000 00001000 "kernel"
mtd5: 00d00000 00001000 "rootfs"
Now run (in this example)
.. code-block:: console
flashcp -v firmware.bin /dev/mtd3
"I know my new image is good, can I skip the intemediate step?"
```````````````````````````````````````````````````````````````
In addition to giving you a chance to see if the new image works, this
two-step process ensures that you're not copying the new image over
the top of the active root filesystem. It might work, or it might
crash in surprising ways.
Flashing from OpenWrt (not currently advised!)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. CAUTION:: At your own risk! This will (at least in some
circumstances) lead to bricking the device: we think this
flash method is currently incompatible with use of a
writeable (jffs2) filesystem.
If your device is running OpenWrt then it probably has the
:command:`mtd` command installed. After transferring the image onto the
device using e.g. :command:`ssh`, you can run it as follows:
.. code-block:: console
mtd -r write /tmp/firmware.bin firmware
For more information, please see the `OpenWrt manual <https://openwrt.org/docs/guide-user/installation/sysupgrade.cli>`_ which may also contain (hardware-dependent) instructions on how to flash an image using the vendor firmware - perhaps even from a web interface.
Updating an installed system (JFFS2)
************************************
Adding packages
===============
If your device is running a JFFS2 root filesystem, you can build
extra packages for it on your build system and copy them to the
device: any package in Nixpkgs or in the Liminix overlay is available
with the ``pkgs`` prefix:
.. code-block:: console
nix-build -I liminix-config=./my-configuration.nix \
--arg device "import ./devices/mydevice" -A pkgs.tcpdump
nix-shell -p min-copy-closure root@the-device result/
Note that this only copies the package to the device: it doesn't update
any profile to add it to ``$PATH``
Rebuilding the system
=====================
:command:`liminix-rebuild` is the Liminix analogue of :command:`nixos-rebuild`, although its operation is a bit different because it expects to run on a build machine and then copy to the host device. Run it with the same ``liminix-config`` and ``device`` parameters as you would run :command:`nix-build`, and it will build any new/changed packages and then copy them to the device using SSH. For example:
.. code-block:: console
liminix-rebuild root@the-device -I liminix-config=./examples/rotuer.nix --arg device "import ./devices/gl-ar750"
This will
* build anything that needs building
* copy new or changed packages to the device
* reboot the device
It doesn't delete old packages automatically: to do that run
:command:`min-collect-garbage`, which will delete any packages not in
the current system closure. Note that Liminix does not have the NixOS
concept of environments or generations, and there is no way back from
this except for building the previous configuration again.
Caveats
~~~~~~~
* it needs there to be enough free space on the device for all the new
packages in addition to all the packages already on it - which may be
a problem if a lot of things have changed (e.g. a new version of
nixpkgs).
* it cannot upgrade the kernel, only userland
Configuration options
*********************
.. _module-options:
.. include:: modules.rst

50
examples/hellonet.nix Normal file
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@ -0,0 +1,50 @@
{ config, pkgs, lib, ... } :
let
inherit (pkgs) serviceFns;
svc = config.system.service;
in rec {
imports = [
../modules/network
../modules/dnsmasq
../modules/ntp
../modules/ssh
];
hostname = "hellonet";
services.int = svc.network.address.build {
interface = config.hardware.networkInterfaces.lan;
family = "inet"; address ="10.3.0.1"; prefixLength = 16;
};
services.ntp = svc.ntp.build {
pools = { "pool.ntp.org" = ["iburst"]; };
makestep = { threshold = 1.0; limit = 3; };
};
services.sshd = svc.ssh.build { };
users.root = {
passwd = "";
};
services.dns =
let interface = services.int;
in svc.dnsmasq.build {
inherit interface;
ranges = [
"10.3.0.10,10.3.0.240"
# ra-stateless: sends router advertisements with the O and A
# bits set, and provides a stateless DHCP service. The client
# will use a SLAAC address, and use DHCP for other
# configuration information.
"::,constructor:$(output ${interface} ifname),ra-stateless"
];
domain = "example.org";
};
defaultProfile.packages = with pkgs; [
figlet
];
}