udev_db must be in a ramfs

udev_db must be in a ramfs

[Ken Brush]

So, I ran a few tests on location of the tdb database (config file:
udev_db variable). And was only able to put in a ramfs location for it.

So my main question is: Is this a bug or a feature? If it's a feature,
I'll just submit a patch for the documentation to prevent people from
trying to put it on a non-ramfs area. If it's a bug, then I would work on
fixing it. :)

-Ken


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Re: udev_db must be in a ramfs

[Kay Sievers]

On Fri, 2004-03-05 at 00:41, Ken Brush wrote:
> So, I ran a few tests on location of the tdb database (config file:
> udev_db variable). And was only able to put in a ramfs location for it.
> 
> So my main question is: Is this a bug or a feature? If it's a feature,
> I'll just submit a patch for the documentation to prevent people from
> trying to put it on a non-ramfs area. If it's a bug, then I would work on
> fixing it. :)

No, it's neither a bug nor a feature. :)
I'm able to place the db wherever I want on the filesystem.
udev doesn't know anything about ramfs, it works on any filesytem.

What is your problem exactly?

thanks,
Kay



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Re: udev_db must be in a ramfs

[Ken Brush]

> On Fri, 2004-03-05 at 00:41, Ken Brush wrote:
>> So, I ran a few tests on location of the tdb database (config file:
>> udev_db variable). And was only able to put in a ramfs location for it.
>>
>> So my main question is: Is this a bug or a feature? If it's a feature,
>> I'll just submit a patch for the documentation to prevent people from
>> trying to put it on a non-ramfs area. If it's a bug, then I would work
>> on
>> fixing it. :)
>
> No, it's neither a bug nor a feature. :)
> I'm able to place the db wherever I want on the filesystem.
> udev doesn't know anything about ramfs, it works on any filesytem.
>
> What is your problem exactly?

I did the following:

udev_db = /tmp/.udev.tdb

And on boot it couldn't find the disklabel, no /dev/hda1 entry, and no
.udev.tdb db.

So, I tried another place /foo.
Same thing

Until I placed a mount -t ramfs none /foo entry in the udev startup script.

So, thinking about it now. /tmp could've been a problem with the db being
lost when /tmp is mounted (i.e. it was created and then a mount over the
top of it.)

Though, if that was the case I wonder why /foo wouldn't work. (unless / is
ro at that point in time.)

Hrm. I'll explore this more.

-Ken


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Re: udev_db must be in a ramfs

[Ken Brush]

Pardon the bad form of replying to myself.

I wrote:
> Though, if that was the case I wonder why /foo wouldn't work. (unless / is
> ro at that point in time.)
>
> Hrm. I'll explore this more.
>

So I ran a quick test, and sure enough it had to do with / being read-only
at the point in time I generate the db. So we may wish to modify the
HOWTO-udev_for_dev to point that out to the less system-aware amongst us.

-Ken


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Re: udev_db must be in a ramfs

[Arnd Bergmann]

On Friday 05 March 2004 01:11, Ken Brush wrote:
> So, I tried another place /foo.
> Same thing
> 
> Until I placed a mount -t ramfs none /foo entry in the udev startup script.
> 
> So, thinking about it now. /tmp could've been a problem with the db being
> lost when /tmp is mounted (i.e. it was created and then a mount over the
> top of it.)

Note that you have to use ramfs for udev_root anyway if you want udev
to work properly, so the database by default ends up in the correct
place as long as udev_db points to a file below udev_root.

	Arnd <><


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