Software Update for Embedded Systems - 林上智
===

{%hackmd LcL4-VI0SGitSiINTuy4rA %}

> 請從這裡開始

## 自介

* https://szlin.me

## 使用 open source 該注意的

* Copyright: [OpenChain](https://www.openchainproject.org)
* [規範書中文版](https://github.com/OpenChain-Project/Specification-Translations/blob/master/zh-Hant/2.0/OpenChain-Specification-2-0-zh-Hant.pdf)
* Patent: [open invention network](https://www.openinventionnetwork.com/)

## Lincese Supporting Tool

- [OpenChain](https://www.openchainproject.org)
- [fossology](https://www.fossology.org/)
- [SPDX](https://spdx.org)

## 為什麼需要firmware upadte?

- bug fixes
- security fixes
- new userspace program
- 例如：glibc的安全漏洞
- Kernel feature enhancement

## LTS (Long Term Stable) Kernel 會出問題?

[cip-kernel-sec](https://gitlab.com/cip-project/cip-kernel/cip-kernel-sec)

## Year 2038 Problem

* 所有的32bit機器的 2038/1/19 都會出現interger overflow
* Glibc 修復進程落後 (Linux Kernel進度相對達預期)

## 可能需要更新的components

Kernelspace
- firmware
- bootloader
- kernel
- device tree

Userspace
- root file system
- application

## 工業用嵌入式Linux裝置的可能行為

- Harsh Environment (第三世界國家)
- 例如：更新到一半沒電掛掉，該如何處理？
- Middle of nowhere
- Bandwidth limited
- 會牽扯到更新機制
- Multiple version supported
- Multiple devices

## Firmeware update的媒介

- 有線網路
- 無線網路
- portable storage (ex: usb drive)
- onsite

## 更新的需求

基本功能
- fail-safe
- roll-back
- exception report
- signatures
- multiple storage type support
- build system integration
- remote access (例如: OTA)

進階功能
- online & offline updates
- encryption
- delta-updates (只更新有需要更新的部份，而不是全部刷掉)
- successful update deletion
- productive updating (建議讓使用者決定時間或在離峰時段)

## 更新的方法

- Image/Block based (全部刷掉)
- File based (只更新有修改的檔案)
- Package based (例如：deb, rpm)
- 可能會多很多dependency
- Delta based (例如：binary diff)
- 複雜度高

## Asymmetric / Symmetric Firmware update

Asymmetric
- 優點
- fail-safe
- 缺點
- downtime

Symmetric
- 優點
- seamless update
- roll-back
- fail-safe
- 缺點
- double copy of OS

## Open Source Software Update Tools

- SWUpdate
- RAUC
- OSTree

###### tags: `COSCUP2019` `BSDTW x Cat System Workshop` `IB306`