Re: [PATCH] Update writing udev rules documentation

[Kay Sievers <kay.sievers@vrfy.org>]

On Sun, 2006-06-04 at 12:57 +0200, Remco wrote:
> > The patch isn't very readable, if anyone wants to review the changes I
> > suggest you just look at the online version as almost all of it has been
> > rewritten:
> > http://www.reactivated.net/writing_udev_rules.html
> > 
> > Comments appreciated.
> > 
> 
> Under 'About this document'
> 
> I don't think hotplug is a requirement nowadays.

Right, almost no recent distro release uses it.

> Under 'Built-in persistent naming schemes'
> 
> I'm not sure this is true but
> '/dev/disk/by-id/usb-Prolific_Technology_Inc._USB_Mass_Storage_Device-part1'
> sounds semi-persistent to me. Imagine you've got two of these memory
> sticks, what names do they get, and how can they be differentiated ? Since I
> don't see a unique id, and unless udev has some trick up it's sleeve, I
> suppose the second device detected will either overwrite the link created
> by the first, or it won't create a link at all.

Sure, by-id is a device property and if you have two identical devices
without any unique property (serial number) the last one discovered
overwrites the link. That's intentional and you better use the
filesystem properties like label or uuid in such case.

> Under 'Putting your rules into action':
> 
> Maybe it's time to replace udevstart with udevtrigger ? Or at least mention
> the udevtrigger/udevsettle combo.

Udevstart is not installed by default and will be removed some day. I
would not even mention it.

> I don't know if it's worthwhile mentioning that if a rule gets changed and
> udevtrigger is run, the new device node / symlinks will be created
> alongside the older existing one(s). Anything created by the old rules will
> stay in place. The old stuff either needs to be removed manually or it will
> disappear when the /dev tree is built from scratch. (probably only after a
> reboot)

No, symlinks are removed if udevtrigger is run a second time for the
same device.

> 
> Under 'Logging'
> 
> AFAICT udev_log is used to set the logging severity. Normally setting it to
> 'err' is probably recommended, 'info' is useful for debugging and will dump
> a lot of information to syslog. If I remember correctly, for this to work,
> some option needs to be set to 'yes' during the build. (like 'make
> USE_LOG=yes' or something similar)

No, that's the default.

Kay



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