On 1/3/13 5:43 PM, Ilya Dmitrichenko wrote:
Hi,
As my day job mostly involves configuring servers using puppet configuration
management system, I had been thinking of what sort of tool would be best to use
on an embedded devices where on some occasions one would want to update a couple
of config files and scripts. Perhaps this can be limited just to the `/etc`
direcotry...
So the best I could come up with so far is to implement it as cron job that
would pull a git repository, perhaps it would also run a script (git hook) that
would restart a daemon or do something of that kind.
I suppose that some people will suggest to just use packages, but I'm not very
keen on maintaining a package repository on some sever out in the internet that
would be one big single point of failure. Although, perhaps, on some occasion,
this may be the only way.
Another reason why I wouldn't like to use git to manage configuration, as that
way all configs are going to be at hand from one directory tree, which is, IMO,
much quicker to manage and validate rather then a recipes spread across
subdirectories.
There are different systems out there that need to be managed (as well as
different philosophies of how to manage them.) Solving all of the problems
isn't going to work. Solving a specific problem has a chance. :)
It's fairly typical that a device can be maintained as files, packages, or
filesystem images. Each of those approaches requires a very different
upgrade/maintenance mechanism. In addition since embedded systems do not have
an admin console, if they fail during the upgrade process you can brick a user,
so a fail safe is almost always required!
In each of the above methods, you can do things like transfer an individual file
(or files) and related reset commands after an upgrade has occurred.. send up a
package (or packages) and automate that -- or even upgrade the filesystem, but
in each of these cases bandwidth may be at a premium. Most field upgrade
systems want a "delta" (diff) based system, where only the changes have to be
sent, not the whole file.
Firstly, I'd appreciate any feedback on this!
And I do have a few rather more specific questions ;)
a) How often OE users do not implement any system updates over the wire in their
products, although the product is able to access the internet?
Due to the complexity of upgrading, this is fairly typical on embedded systems
in my experience...but it's being tolerated less and less over time. (They
usually have some kind of an upgrade mechanism, they just don't do it over the
internet.)
b) Has anyone here use the configuration tools like puppet, chef or cfendgine
and understands the benefits?
c) Has anyone succeeded building git without having to include perl on the
target? I'd probably get ways with just a subset of git commands.
I have also had a look at libgit2, but not sure if I'd be able to implement
something as robust as git itself with libgit2...
Last time I looked (a few months back) it was not possible to build a functional
git system w/o perl -- or at least I wasn't able to. I hope this continues to
get better, as perl is -very- heavy weight for an embedded system.
So if you want the ultimate works for everyone system.. it really needs to be a
field upgrade tool of some kind. Basically providing the infrastructure to
push/pull the update, a way to use a delta of the update to what is already
installed on the device to construct the "file" to save bandwidth, a way to
apply the update and control the associated behavior. Then people can use that
to implement file, package or image based upgrades... fail safe behavior is also
usually device specific and would be implemented based on the toolkit.
Cheers,
--
Ilya
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