On 2015-05-11 08:48, Arnoud Onnink wrote:
Dear RedSleeve users,
Unfortunately many embedded GNU/Linux users have limited choice in
what kernel version they want to run, due to manufacturer-specific
hacks that can't be ported, binary-only drivers, missing sources (GPL
violations), etc. At the moment there are a lot of otherwise perfectly
hackable devices out there that are stuck on 2.6 series Linux.
I am, indeed, painfully aware of that.
For these users it would be very nice if distros like RedSleeve could
be crystal clear on which kernels are supported, and which are not. On
the Wiki I could not find such info.
Perhaps I should put this on the wiki, I'm just not sure what the
wording should be. In a nutshell:
1) No kernels are supported - use and take your chances with whatever
you can get working.
2) Most kernels will in fact work just fine.
The general recommendation is to use whatever kernel shipped with
your device. Since most devices suitable for RedSleeve came
pre-configured with some kind of a Linux derivative, this generally
works for most people. Any kernel updates extracted from the device
manufacturer's firmware updates should equally work.
The main caveat here is that most manufacturers of ARM based
devices either abandon any and all support of them as soon as the
product is out the door, or exit the market for whatever reason,
with the same end result.
The main problem with using old, stagnant kernels, is that every
once in a while a kernel bug is discovered that can under certain
circumstances security implications. While these are almost never
directly exploitable remotely, it is nevertheless important to at
least be aware of potential problems and exercise appropriate care
if the device is exposed directly to the internet.
Specifically, what is the minimal kernel version needed to run the
RedSleeve rootfs? Are there any options that must be enabled?
This is a good question, but unfortunately one that I cannot give
an actual specific answer to. EL6 ships with 2.6.32, so the bare
minimal requirements in terms of version are most definitely no
higher than that. Older kernels most likely work but I am not of
anyone having tested the actual lowest version limit that will work.
In terms of build options, again, I don't think anyone ever looked
into it, but any kernel that shipped with any ARM device I have
tried using since work on the RedSleeve project began, even heavily
stripped down kernels from devices that only ship with Android or
NAS-es, or Chromebooks, has worked just fine.
Given that this is generally pretty trivial to test when you are
getting your device up and running, the default advice to try the
kernel you have for the device first is generally sound. Once you
have something working, it is generally much easier to start
looking into what better kernel you might be able to build from
sources and get working.
If anyone can supply me with this info (or a link), I will add it to
the Wiki. I'm guessing it's going to be similar to the CentOS kernel
requirements, but I may be wrong.
Do you have a link to the list of CentOS kernel requirements?
I am curious becaue either that list is extremely basic, to the
point where every kernel that ships with any device I own fulfills
it, or the list is pessimistically large and the basic userspace
works just find with more cut down kernels.
Gordan
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