Openwrt for embedded system learning and other system architecture comparison
The following table compares the OpenWrt system architecture with other system architectures:
1. From the above table, we can see that the main advantage of openwrt is small. It runs at least 32M of memory, and the minimum size of FW is 8M. It can meet the requirements of most assembly instruction sets, so it comes from hardware cost. Said, openwrt operating system can be adapted to smaller products with memory and flash. For smart products with relatively simple functions, openwrt has its unique advantages.
2. Not only that, openwrt supports the use of the same Linux kernel as other operating systems (Desktop Distributions/android), including support for 802.11, which also gives it more room for wireless development.
3. The C library used by openwrt is uClibc, not glibc. It is a small C standard library for embedded Linux systems. uClibc is smaller than the C library GNU C Library (glibc) which is generally used for Linux distributions. Much, glibc aims to support all C standards for the widest range of hardware and kernel platforms, while uClibc focuses on embedded Linux. Many features can be traded off based on space requirements.
4. In openwrt, the file system startup and management are somewhat different from those of other systems, and in the latest version, the daemon process with higher aggregation is used for control. The general file system startup starts from the init process. From the following table, we can see that different operating systems start different processes. Even the same "operating system", the startup mode between the old and new versions is also Not the same, such as openwrt, the old version of the bosybox inside some of the functions integrated in the procd, hotplug2 on the hot plug event monitoring and ubox to replace, crond still use the busybox inside, ubus is a simplified version of dbus, The simple API interface is more suitable for embedded platforms.
5. netifd is used to monitor and configure network information.
6. libubox is some management tool
7. opkg is a tool for installing some applications in openwrt, just like apt-get in ubuntu, apk in Android
In general, running an openwrt system requires at least one 32M memory + 8M flash, which supports the Linux kernel. The main management tools for the new version of the file system include procd, ubox, ubus, netifd and opkg.
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