describe how to flash Liminix, and kexecboot

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Daniel Barlow 2023-03-24 23:38:41 +00:00
parent f5a7b78679
commit 608d750b60
1 changed files with 135 additions and 19 deletions

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@ -9,39 +9,155 @@ Configuring for your use case
You need to create a ``configuration.nix`` that describes your router
and the services that you want to run on it. Start by copying
``vanilla-configuration.nix`` and adjusting it.
``vanilla-configuration.nix`` and adjusting it, or look in the `examples`
directory for some pre-written configurations.
If you want to create a configuration that can be installed on
a hardware device, be sure to include the "flashable" module.
.. code-block: nix
imports = [
Building and flashing
You need to set ``<liminix-config>`` to point to your
``configuration.nix``, the file for your hardware device definition as
argument ``device``, and to choose an appropriate output attribute
depending on what your device is and how you plan to install onto
it. For example:
An example command to build Liminix might look like this:
.. code-block:: console
nix-build -I liminix-config=./tests/smoke/configuration.nix --arg device "import ./devices/qemu" -A outputs.default
nix-build -I liminix-config=./tests/smoke/configuration.nix \
--arg device "import ./devices/qemu" -A outputs.default
``outputs.default`` is intended to do something appropriate for the
device, whatever that is. For the qemu device, it creates a directory
containing a squashfs root image and a kernel.
In this command ``<liminix-config>`` points to your
``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.
Future versions of this manual will at this point refer to
device-specific instructions for installing Liminix using the router's
Web UI or other non-invasive method. As of Feb 2023, the only way to
flash a device is to take the cover off and connect wires to the
serial console pads - so, check in the Developer Manual.
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 `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
Updating a running device
Flashing with :command:`flashcp`
Feature forthcoming.
This requires an existing Liminix system, or perhaps some other
operating system on the device which provides the :command:`flashcp`
command. You need to locate the "firmware" partition, which you can do
with a combination of :command:`dmesg` output and the contents of
Module options
.. 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"
Then you can copy the 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 -
and then connect to the device and run
.. code-block:: console
flashcp firmware.bin /dev/mtd3
Flashing from OpenWrt (untested)
If your device is running OpenWrt then it probably has the
:command:`mtd` command installed and you can use it as follows:
.. code-block:: console
mtd -r write /tmp/firmware_image.bin firmware
For more information, please see the `OpenWrt manual <>`_
Flashing from the boot monitor
If you are prepared to open the device and have a TTL serial adaptor
or some kind to connect it to, you can probably flash it using U-Boot.
This is quite hardware-specific: please refer to the Developer Manual.
Updates to running devices
To mitigate the risk of flashing a new configuration and potentially
render the device unresponsive if the configuration is unbootable or
doesn't bring up a network device, Liminix has a
"try before write" mode.
To test a configuration without writing it to flash, import the
``kexecboot`` module and 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 `` 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 ./ .
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. Thus, by combining kexec
boot with a hardware watchdog you can try new images with very little
chance of bricking anything. When you are happy that the new
configuration is correct, build and flash a flashable image of it.
Module options (tbd)