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by kevin_thibedeau 3516 days ago
> why are we defining portability at the operating system level when network portability works so much better

A lightweight POSIX-capable system has real value today. Operating systems need to be in more places than just the data center. IoT devices don't have the resources to run a VM or any other fancy containerized environment. POSIX was designed to be used on systems with comparable resources to what many embedded processors now have. It makes sense to leverage the existing codebase where possible.
2 comments
jprzybyl 3516 days ago
> POSIX was designed to be used on systems with comparable resources to what many embedded processors now have.

But not comparable environments. Most IOT environments are very small parts of very big systems, and POSIX defines a system with a teletype and a line editor.

I seriously doubt the value of the existing codebase. Saying code made for a server (like most existing unix code!) is fine for IOT feels wrong, and not just because IOT devices have kilobytes of memory and servers can have gigabytes/terabytes.

I don't think that a universal OS can work well when we know that universal programming languages, data transfer protocols, and everything else didn't. Imagine if we were still doing everything in PL/I. We recognize now that different programming tasks need different programming environments, but we still don't think that different programs need different program environments. It's just strange to me.

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kevin_thibedeau 3516 days ago
> Saying code made for a server (like most existing unix code!) is fine for IOT feels wrong,

There was a time when people ran Linux/SunOS/Ultrix/etc. with tiny amounts of RAM and swap. It's not unusual for an embedded device to have 8, 16, 32 MiB, or more RAM available. Many traditional *nix programs can run unchanged on such hardware.

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cmrdporcupine 3515 days ago
I think the parent's comment was more along the lines of: just because an embedded device _can_ run a Unix doesn't mean it should have to adopt the semantics and history of the *Unix environment that POSIX mandates. In particular the model of TTYs, filesystems, Unix-style file/IO, Unix-style virtual memory / mmap, etc. It's not that this stuff is expensive on modern embedded systems (which as pointed out often have the hardware capacity of high end systems from 20 years ago), it's that these capabilities are either not needed, or impose a conceptual model of what a computer and operating system have to be that don't match up to what the machine is designed for.
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nickpsecurity 3515 days ago
There's a whole market of suppliers that's been going strong for decades. Especially for safety-critical embedded with untrusted, Linux/POSIX apps in separate partitions. QNX is one of best examples far as commercial adoption:

http://www.qnx.com/content/qnx/en/products/neutrino-rtos/neu...

Example of embedded product in case you wonder about performance cost of all that isolation, healing, and context switching:

https://youtu.be/vPo6gl8N0wM?t=1m20s

EDIT to add the QNX Desktop Demo that came on a single floppy. Throwing it in since you were mentioning resource-constrained systems further down. A floppy is 1.44MB with base QNX running in ROM's of embedded systems. Can scale such architectures it up or down however you wish. :)

http://crackberry.com/heres-how-qnx-looked-1999-running-144m...

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