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From: Rich Morin <rdm@cfcl.com>
To: TUHS main list <tuhs@minnie.tuhs.org>
Subject: Re: [TUHS] Abstractions
Date: Sun, 21 Feb 2021 03:08:25 -0800	[thread overview]
Message-ID: <4375BA78-1F3A-4106-8FAB-1AFC77B8630B@cfcl.com> (raw)
In-Reply-To: <CAKH6PiXW80gL1Hy7nVTrZ1Wm-zbKZGUj8+T8Ui4cjWdW=vV1LA@mail.gmail.com>

> On Feb 20, 2021, at 15:09, M Douglas McIlroy <m.douglas.mcilroy@dartmouth.edu> wrote:
> 
>> - separation of code and data using read-only and read/write file systems
> 
> I'll bite.  How do you install code in a read-only file system?

Disclaimer: I haven't actually used Nerves myself, just watched some presentations, read various web pages, etc.  So anything I say about it is quite unreliable.  And, although that item was (sort of) true, it was obviously rather misleading if interpreted too broadly.  So, I'll try to provide some context to explain what I meant by it.

As I understand it, Nerves is intended as a build and delivery mechanism for IoT system software.  It's supposed to be possible to upgrade a deployed device without blowing away its persistent saved state.  And, if the upgrade fails, to back down to the previous version.  Also, the running code on the device should not be able to trash the system software.

To support this, they use multiple file systems, with various updating attributes.  For example, they might have two file systems for the system software and a third one for the persistent saved state.  This lets a developer upload and boot a new copy of the system software, but fall back to the old version if something goes wrong.

-r


  parent reply	other threads:[~2021-02-21 11:08 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-20 23:09 M Douglas McIlroy
2021-02-21  8:15 ` Otto Moerbeek
2021-02-21 11:08 ` Rich Morin [this message]
2021-02-21 22:40 ` Dave Horsfall
2021-02-21 23:01   ` Steve Nickolas
2021-02-23  3:31     ` Andrew Warkentin
2021-02-23 17:29       ` [TUHS] /usr separation (was: Abstractions) Greg A. Woods
2021-02-23 18:28         ` [TUHS] /usr separation Grant Taylor via TUHS
2021-02-23 18:57           ` Theodore Ts'o
2021-02-23 20:29             ` Grant Taylor via TUHS
2021-02-24 14:14               ` Theodore Ts'o
2021-02-24 17:50                 ` Grant Taylor via TUHS
2021-02-24 18:37                   ` Theodore Ts'o
2021-02-24 18:48                     ` Grant Taylor via TUHS
2021-02-25  3:38                       ` Theodore Ts'o
2021-02-24 20:25                     ` Steve Nickolas
2021-02-24 22:08                       ` Steffen Nurpmeso
2021-02-24  3:12         ` [TUHS] /usr separation (was: Abstractions) Andrew Warkentin
2021-02-22  0:13   ` [TUHS] Abstractions Warren Toomey
2021-02-27  2:47     ` Dave Horsfall
2021-02-23  0:25   ` Wesley Parish
2021-02-23  0:38     ` Steve Nickolas
2021-02-23  2:50       ` Theodore Ts'o
2021-02-23  3:19         ` Warner Losh
2021-02-23  1:47     ` Theodore Ts'o
2021-02-21 22:54 ` Clem Cole
  -- strict thread matches above, loose matches on Subject: below --
2021-02-24  4:18 Rudi Blom
2021-02-23 19:37 Nelson H. F. Beebe
2021-02-23 21:02 ` Charles H. Sauer
2021-02-23 21:15   ` Henry Bent
2021-02-24  2:47     ` Greg A. Woods
2021-02-24  3:20       ` Warner Losh
2021-02-24 20:05         ` Greg A. Woods
2021-02-24  1:51 ` Greg A. Woods
2021-02-24  2:23   ` Nelson H. F. Beebe
2021-02-21 10:47 Paul Ruizendaal
2021-02-15 19:56 Jon Steinhart
2021-02-15 21:52 ` Dave Horsfall
2021-02-16  7:13   ` arnold
2021-02-16  8:15 ` Tom Ivar Helbekkmo via TUHS
2021-02-16 10:04   ` Wesley Parish
2021-02-16 19:59   ` Jon Steinhart
2021-02-17  4:01     ` Theodore Ts'o
2021-02-17  6:50     ` Chris Hanson
2021-02-16 12:26 ` Rich Morin
2021-02-16 22:46 ` Steffen Nurpmeso
2021-02-17 12:09 ` David Arnold

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