Re: [DNG] new behaviour of /dev

2017-08-23 Thread Rick Moen 
Quoting Renaud OLGIATI (ren...@olgiati-in-paraguay.org):

>  'solitary, poor, nasty, brutish, and short' come to mind

The long-lamented ntk.net ('Need to Know') newsletter carried a cheeky
subhead declaring itself 'nasty, British, and short'.  All readers of
Hobbes cheered.

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Re: [DNG] new behaviour of /dev

2017-08-23 Thread Ron 
On Wed, 23 Aug 2017 17:48:02 +0200
Alessandro Selli  wrote:

> >>   People were happy even before the steam engine was invented.

> >  'solitary,  

>  Do you think so?

> > poor,  

>   It depends; when the wealthiest individuals where those who could afford a
> horse, wealth was more evently distributed than today.  Or do you think they
> felt poor because they could not have a PC?

> > nasty,  

>   Maybe, some of them.

> > brutish,  

>   Maybe, some of them.

> > and short' come to mind  

>   Oh dear, were they really *short*?  Jeez, how happy I am not to have lived
> in those awful times!

All those adjectives, which come from a quote of Thomas Hobbes (1588 – 1679) 
refer not to people, but to their lives in preceding ages...
 
Cheers,
 
Ron.
-- 
Gli nomini si debbano o vezzeggiate o peguere;
 perche' si vendiciano delle leggieri offese,
   delle gravi non possono.
-- Niccolo Machiavelli

   -- http://www.olgiati-in-paraguay.org --
 
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Re: [DNG] new behaviour of /dev

2017-08-23 Thread Alessandro Selli 
On Wed, 23 Aug 2017 at 05:22:20 -0400
Renaud (Ron) OLGIATI  wrote:

> On Wed, 23 Aug 2017 09:24:28 +0200
> Alessandro Selli  wrote:
> 
>>> I really don't know why so many people think hotplugging is a major
>>> need, anyway.  I happily used Linux for a very long time before it
>>> existed.  
>
>>   People were happy even before the steam engine was invented.  
>
>  'solitary,

 Do you think so?

> poor,

  It depends; when the wealthiest individuals where those who could afford a
horse, wealth was more evently distributed than today.  Or do you think they
felt poor because they could not have a PC?

> nasty,

  Maybe, some of them.

> brutish,

  Maybe, some of them.

> and short' come to mind

  Oh dear, were they really *short*?  Jeez, how happy I am not to have lived
in those awful times!

> Cheers,

  Just think what people will think of this generation in ~200 years time,
provided mankind does not self-destruct before: "how could people back in the
2000s possibily be happy without the many things we take for granted?  And how
*shorter* they were compared to us now!  Nasty, brutish and smelly short
boors!"

> Ron.

Alessandro

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Re: [DNG] new behaviour of /dev

2017-08-23 Thread Ron 
On Wed, 23 Aug 2017 09:24:28 +0200
Alessandro Selli  wrote:

> > I really don't know why so many people think hotplugging is a major
> > need, anyway.  I happily used Linux for a very long time before it
> > existed.

>   People were happy even before the steam engine was invented.

 'solitary, poor, nasty, brutish, and short' come to mind
 
Cheers,
 
Ron.
-- 
 It is inexcusable for scientists to torture animals;
   let them make their experiments on journalists and politicians.
   -- Henrik Ibsen

   -- http://www.olgiati-in-paraguay.org --
 
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Re: [DNG] new behaviour of /dev

2017-08-23 Thread Alessandro Selli 
On 22/08/2017 at 15:22, Rick Moen wrote:

> I really don't know why so many people think hotplugging is a major
> need, anyway.  I happily used Linux for a very long time before it
> existed.

  People were happy even before the steam engine was invented.


Alessandro
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Re: [DNG] new behaviour of /dev

2017-08-22 Thread Rick Moen 
Quoting Didier Kryn (k...@in2p3.fr):

> This is the result of enabling devtmpfs when building the
> kernel. Devtmpfs was implemented a few years ago and is, in my
> opinion, a reaction to the bad behaviour of Udev developers.

Plausible.

> For the same reason (explicitly), the kernel now loads the firmware
> automatically instead of requesting it to the hotplugger.

And this _definitely_ seemed to be a reaction to systemd/udev
developers' bad behaviour.  I [half-]remember when it happened; it was a
reaction to a specific bit of coder insanity, maybe that kdbus episode?

> Definitely, the hotplugger has less and less to do, and, definitely,
> I think Mdev could do it pretty well.

And simply.  You just create a custom hotplug handler script
/sbin/hotplug (the default value of /proc/sys/kernel/hotplug as decreed
in the kernel configuration) like this:

#!/bin/sh
test -n "$MODALIAS" && modprobe "$MODALIAS";
exec /sbin/mdev

However, for my own needs, I personally favour just compiling needed
drivers into the Linux kernel monolithically.  (Yes, average desktop
user cannot be expected..., blah, blah, blah.)

I really don't know why so many people think hotplugging is a major
need, anyway.  I happily used Linux for a very long time before it existed.


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Re: [DNG] new behaviour of /dev

2017-08-22 Thread Didier Kryn 

Le 22/08/2017 à 01:27, Adam Borowski a écrit :

Hi!
Do you remember when for decades we had to populate /dev using mknod
(using makedev or something) -- both on Linux and on Unices that predated
it?  Then when udev came to make device creation dynamic.

I just installed a new server, not using d-i but manual debootstrap.  Not
even regular debootstrap but with --variant=minbase as --exclude is still
buggy and fails to exclude THE THING THAT SHOULDN'T BE NAMED.  Everything
worked fine, except for one detail: somehow /dev/ttyUSB* were mode 600
root:root instead of 660 root:dialout.

Turns out, udev was not installed.  Nor mdev, nothing.  No initrd either.
Yet it boots and works correctly.  fstab has no entries except for / -- and
even this is pointless if you mount rootfs rw on cmdline (the ro + remount
dance does nothing good on any modern fs other than ext4).  If there was any
userland configuration, it is done by openrc by default.

Hotplugging USB devices seems to work fine, new nodes get created without
udev's involvement.

Obviously, I guess running without udev is a bad idea in the long run -- you
want correct permissions to get applied, hotplug hooks to be run, etc.  But
this suggests 90% of udev/mdev/vdev code can be thrown out.

That the kernel can now do most of this work by itself is news to me.

This is the result of enabling devtmpfs when building the kernel. 
Devtmpfs was implemented a few years ago and is, in my opinion, a 
reaction of the bad behaviour of Udev developpers. For the same reason 
(explicitely), the kernel now loads the firmware automatically instead 
of requesting it to the hotplugger. Definitely, the hotplugger has less 
and less to do, and, definitely, I think Mdev could do it pretty well.


Didier

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