# UBootEnv
[](https://circleci.com/gh/nerves-project/uboot_env)
[](https://hex.pm/packages/uboot_env)
This library lets you read and write [U-Boot](https://www.denx.de/wiki/U-Boot)
environment blocks from Elixir. U-Boot environment blocks are simple key-value
stores used by the U-Boot bootloader and applications that need to communicate
with it. Nerves uses U-Boot environment blocks to store settings related to the
device and running firmware. Nerves uses the format even for boards (like the
Raspberry Pis) that don't use the U-Boot bootloader.
This library has the following features:
* Create, read, and write to U-Boot environment blocks in pure Elixir with OTP
21 and later
* Load environment block configurations from `/etc/fw_env.config`
* Redundant and non-redundant environment block support
This library does not support U-Boot environment blocks stored in raw NAND Flash
or big-endian blocks.
## Installation
Install by adding `uboot_env` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:uboot_env, "~> 1.0"}
]
end
```
## Using
Here's an example of reading the environment:
```elixir
iex> UBootEnv.read()
{:ok,
%{
"fdt_addr" => "0x83000000",
"stdout" => "serial",
...
}
}
```
To change the environment, update the map returned by `UBootEnv.read/0` and call
`UBootEnv.write/1`. If you're used to using `fw_setenv`, note that
`UBootEnv.write/1` writes the map that you give it whereas `fw_setenv` merges
the key value pairs with the current environment.
```elixir
iex> {:ok kv} = UBootEnv.read()
iex> new_kv = Map.put(kv, "hello", "world")
iex> UBootEnv.write(new_kv)
:ok
```
`UBootEnv.read/0` and `UBootEnv.write/1` do not perform any locking of the data
they write. If you have multiple processes updating the U-Boot environment
block, you'll have to synchronize access to it.
## License
This code is Apache 2 licensed.
