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Old 01-10-2008, 05:53 PM
"Arthur Pemberton"
 
Default Linux is not about choice

On Jan 10, 2008 12:45 PM, Chris Adams <cmadams@hiwaay.net> wrote:
> Once upon a time, David Zeuthen <david@fubar.dk> said:
> > On Thu, 2008-01-10 at 10:40 -0600, Arthur Pemberton wrote:
> > > We are badly in need of system-config-udev. I spent several hours
> > > understanding udev adn building rules for my sound cards and tv cards.
> > > I hadn't done a yum update on my F7 box for weeks/months (lazyness)
> > > did one this week, and it apperently just blew away my custom udev
> > > config
> >
> > Hell no. We are in badly need of this crap just working out of the box.
>
> And how do you know automatically that one of my USB-to-RS232 adapters
> is my UPS (should be /dev/ups), one is my GPS (/dev/gps0), and one is a
> cell phone (/dev/modem)?

I have no idea myself, and I have spent a few hours pondering the
problem. The only solution I have come up with is to keep things as
they are, but generate symantic aliases for them.

Example:

/dev/video1 -> /dev/video_hauppauge_iptv

Far from perfect however, but would be adequate for my needs.


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Old 01-10-2008, 06:02 PM
David Zeuthen
 
Default Linux is not about choice

On Thu, 2008-01-10 at 12:45 -0600, Chris Adams wrote:
> Once upon a time, David Zeuthen <david@fubar.dk> said:
> > On Thu, 2008-01-10 at 10:40 -0600, Arthur Pemberton wrote:
> > > We are badly in need of system-config-udev. I spent several hours
> > > understanding udev adn building rules for my sound cards and tv cards.
> > > I hadn't done a yum update on my F7 box for weeks/months (lazyness)
> > > did one this week, and it apperently just blew away my custom udev
> > > config
> >
> > Hell no. We are in badly need of this crap just working out of the box.
>
> And how do you know automatically that one of my USB-to-RS232 adapters
> is my UPS (should be /dev/ups), one is my GPS (/dev/gps0), and one is a
> cell phone (/dev/modem)?

Either we look at the USB device it's hanging off (vendor, product or
class id's), the driver or we provide a simple interface in
gnome-device-manager or similar (including command line apps) to set it.

For the latter, there is going to be some development for F10, F11 and
later in merging the hal and udev databases into a common device
database that will feature persistent properties (such as classification
and device naming) keyed off by-path, by-id and so on to easily make a
feature like this available. That's the answer to this (very real)
problem, not a silly program that generates udev rules.

David


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Old 01-10-2008, 06:04 PM
David Zeuthen
 
Default Linux is not about choice

On Thu, 2008-01-10 at 12:48 -0600, Les Mikesell wrote:
> It doesn't disambiguate the situation unless you are saying that local
> administrators should not touch any files. How does a (novice or not)
> user know which files belong to him but are delivered as working
> defaults and which will be clobbered by subsequent updates? I thought
> most of the point of splattering stuff under /etc/sysconfig was to have
> a place to put distribution-tool managed bits without too much impact on
> standard, documented config files as they would work in other distributions.

The problem is that a lot of software erroneously place files in /etc.
Ideally all files (and that should be very few files!) in /etc should be
safe to edit by the system administrator.

David


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Old 01-10-2008, 06:28 PM
"Arthur Pemberton"
 
Default Linux is not about choice

On Jan 10, 2008 1:02 PM, David Zeuthen <david@fubar.dk> wrote:
>
> On Thu, 2008-01-10 at 12:45 -0600, Chris Adams wrote:
> > Once upon a time, David Zeuthen <david@fubar.dk> said:
> > > On Thu, 2008-01-10 at 10:40 -0600, Arthur Pemberton wrote:
> > > > We are badly in need of system-config-udev. I spent several hours
> > > > understanding udev adn building rules for my sound cards and tv cards.
> > > > I hadn't done a yum update on my F7 box for weeks/months (lazyness)
> > > > did one this week, and it apperently just blew away my custom udev
> > > > config
> > >
> > > Hell no. We are in badly need of this crap just working out of the box.
> >
> > And how do you know automatically that one of my USB-to-RS232 adapters
> > is my UPS (should be /dev/ups), one is my GPS (/dev/gps0), and one is a
> > cell phone (/dev/modem)?
>
> Either we look at the USB device it's hanging off (vendor, product or
> class id's), the driver or we provide a simple interface in
> gnome-device-manager or similar (including command line apps) to set it.

You're wierd dude, this essentially the same thing I suggested and you
discouraged.

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Old 01-10-2008, 06:44 PM
Les Mikesell
 
Default Linux is not about choice

David Zeuthen wrote:

OK, that's at least partly right but you forgot to tell me what to call
the device when creating the label for filesystems that support it - or
what name to use for access to the raw device for operations like image
copies and addition/removal from raid arrays. The underlying problem
can't be solved at the filesystem layer.


Uhm. Did you *even* look at /dev/disk? There's by-path, by-uuid,
by-label and so forth.


I'm looking, but I don't see consistency anywhere across linux kernels.
by-uuid, by-label seem to only refer to things that have been created
by some other access, by-id doen't always appear, and by-path varies
across kernels as the device drivers have changed. Where is something
better than device driver major/minor numbers would have been?


> Heck, SUSE/Ubuntu ships udev rules for making the

md and dm devices use persistent naming too. Maybe if the distros were
better at working together at the plumbing layer (another rant of
mine)), this would be all standardized. Eventually it will all be
standardized.


Do you expect this to be standardized only for Linux or is there hope
for a Posix specification for device name conventions?



No, Fedora is about being on the bleeding edge and creating a system
where you don't *need* to migrate configuration files because the files
will be correct if they are using stable identifiers for devices.
I haven't found that to be the case. And I don't see any reason for
today's experimental change to end up being the one that sticks.


There's nothing experimental about the path modern Linux is going in
wrt. to device naming. If you had bothered you will fine that more and
more device classes, including the infamous video4linux camp, is moving
to persistent device names.


If I had bothered to what? Is this documented somewhere? Is it
version-specific to fedora?



It's true, however, that Fedora is
super-reluctant on taking advantage of what happens upstream and keep
using pre-2000 technology. That's, very slowly, changing though.


Much of my data is on filesystems created before 2000. Will changing
the names used to reference them make them work better?


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Old 01-10-2008, 06:51 PM
David Zeuthen
 
Default Linux is not about choice

On Thu, 2008-01-10 at 13:44 -0600, Les Mikesell wrote:
> > Uhm. Did you *even* look at /dev/disk? There's by-path, by-uuid,
> > by-label and so forth.
>
> I'm looking, but I don't see consistency anywhere across linux kernels.
> by-uuid, by-label seem to only refer to things that have been created
> by some other access, by-id doen't always appear, and by-path varies
> across kernels as the device drivers have changed. Where is something
> better than device driver major/minor numbers would have been?

You should use by-uuid. If you see other entries change according to
what kernel you are using this should be reported on the udev list

linux-hotplug@vger.kernel.org

and please follow up there with other questions too (it's getting
off-topic in this thread and even this list). Thanks.

> Do you expect this to be standardized only for Linux or is there hope
> for a Posix specification for device name conventions?

No, I don't expect this to be standardized outside Linux.

> > There's nothing experimental about the path modern Linux is going in
> > wrt. to device naming. If you had bothered you will fine that more and
> > more device classes, including the infamous video4linux camp, is moving
> > to persistent device names.
>
> If I had bothered to what? Is this documented somewhere? Is it
> version-specific to fedora?

That's like asking if all the sysfs are documented somewhere and the
answer to questions like that are normally "no, it's self-evident" (and
I agree it's not always the case) or "look at the source". Anyway, by
all means, send patches to the udev list with docs if you think it's
required.

> > It's true, however, that Fedora is
> > super-reluctant on taking advantage of what happens upstream and keep
> > using pre-2000 technology. That's, very slowly, changing though.
>
> Much of my data is on filesystems created before 2000. Will changing
> the names used to reference them make them work better?

This question doesn't really make sense to me. What I'm telling you is
to use persistent device names. That entails having UUID and/or labels
on your file systems. So if you don't have that, by all means, go ahead
and create them and things will start appearing under /dev/disk.

Anyway, please use the udev list for further questions. This thread is
getting too long. Thanks.

David


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Old 01-10-2008, 06:57 PM
Les Mikesell
 
Default Linux is not about choice

Arthur Pemberton wrote:


Hell no. We are in badly need of this crap just working out of the box.

And how do you know automatically that one of my USB-to-RS232 adapters
is my UPS (should be /dev/ups), one is my GPS (/dev/gps0), and one is a
cell phone (/dev/modem)?

Either we look at the USB device it's hanging off (vendor, product or
class id's), the driver or we provide a simple interface in
gnome-device-manager or similar (including command line apps) to set it.


You're wierd dude, this essentially the same thing I suggested and you
discouraged.


The system can't possibly work with multiple choices unless you have an
interface to let a human configure which is which. Now the kicker is
that most of my machines are in remote locations with swappable drives
and I expect to be able to ship a pre-configured drive built locally and
have someone pop it in a known controller position and have it come up
working - and to be able to copy images that will work across a number
of identical machines without individual attention other than setting
the hostname and IP addresses.


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Old 01-10-2008, 06:58 PM
David Zeuthen
 
Default Linux is not about choice

On Thu, 2008-01-10 at 14:51 -0500, David Zeuthen wrote:
> > > There's nothing experimental about the path modern Linux is going in
> > > wrt. to device naming. If you had bothered you will fine that more and
> > > more device classes, including the infamous video4linux camp, is moving
> > > to persistent device names.
> >
> > If I had bothered to what? Is this documented somewhere? Is it
> > version-specific to fedora?
>
> That's like asking if all the sysfs are documented somewhere and the
> answer to questions like that are normally "no, it's self-evident" (and
> I agree it's not always the case) or "look at the source". Anyway, by
> all means, send patches to the udev list with docs if you think it's
> required.

I wasn't really clear here; I meant if you had followed udev and kernel
lists you would see a trend that more and more devices will start using
udev rules to provide persistent device names. Hope this clarifies.

David


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Old 01-10-2008, 07:13 PM
"Arthur Pemberton"
 
Default Linux is not about choice

On Jan 10, 2008 1:57 PM, Les Mikesell <lesmikesell@gmail.com> wrote:
> Arthur Pemberton wrote:
>
> >>>> Hell no. We are in badly need of this crap just working out of the box.
> >>> And how do you know automatically that one of my USB-to-RS232 adapters
> >>> is my UPS (should be /dev/ups), one is my GPS (/dev/gps0), and one is a
> >>> cell phone (/dev/modem)?
> >> Either we look at the USB device it's hanging off (vendor, product or
> >> class id's), the driver or we provide a simple interface in
> >> gnome-device-manager or similar (including command line apps) to set it.
> >
> > You're wierd dude, this essentially the same thing I suggested and you
> > discouraged.
>
> The system can't possibly work with multiple choices unless you have an
> interface to let a human configure which is which. Now the kicker is
> that most of my machines are in remote locations with swappable drives
> and I expect to be able to ship a pre-configured drive built locally and
> have someone pop it in a known controller position and have it come up
> working - and to be able to copy images that will work across a number
> of identical machines without individual attention other than setting
> the hostname and IP addresses.


I would have thought that with dirves you can jsut mount by labels,
does this not work for your use case?

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Old 01-10-2008, 07:16 PM
Alan Cox
 
Default Linux is not about choice

On Thu, Jan 10, 2008 at 11:00:24AM -0600, Les Mikesell wrote:
> But the old names were predictable; the new ones aren't - when I move a
> disk to a new controller/drive position, I know about it.

They were not. If you added a controller they may change.

Old unix naming is based on a fixed structure, modern system naming is
based on the reality of hotplug

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