Failed to Create Symlinks ...

Failed to Create Symlinks ...

[Chris Dellin]

Hey all,

I'm having some trouble recently with my installation of udev.  I
expect it to create symlinks for a few devices, but no symlinks are
created.  For example:

udev should create a symlink, as per the rule below:
$ grep agpgart /etc/udev/rules.d/50-udev.rules
KERNEL="agpgart", NAME="misc/%k", SYMLINK+="%k"

However, on boot, no symlink exists (although the /dev/misc/agpgart
device is properly created).

Once booted, the symlink does exist in the udev database:
# udevadm info --export-db | grep -A 8 'P: /devices/virtual/misc/agpgart'
P: /devices/virtual/misc/agpgart
N: misc/agpgart
S: agpgart
E: UDEV_LOG=3
E: DEVPATH=/devices/virtual/misc/agpgart
E: MAJOR\x10
E: MINOR\x175
E: DEVNAME=/dev/misc/agpgart
E: DEVLINKS=/dev/agpgart

I don't quite know how to interpret the results from udevtest, but the
results are here:
http://dellin.net/static/temp/udevtest_output.txt

A few other notes:
 - The system is running a recent copy of Gentoo Linux.
 - This started happening when I upgraded my kernel from 2.6.29.5 to 2.6.31.6.
 - The /dev/video0 symlink has the same problem; it should be linked
to /dev/v4l/video0, which is created correctly.

Any ideas?
- Chris

Christopher Dellin
cdellin@gmail.com

Re: Failed to Create Symlinks ...

[Kay Sievers]

On Sat, Nov 28, 2009 at 23:52, Chris Dellin <cdellin@gmail.com> wrote:
> I'm having some trouble recently with my installation of udev.  I
> expect it to create symlinks for a few devices, but no symlinks are
> created.  For example:
>
> udev should create a symlink, as per the rule below:
> $ grep agpgart /etc/udev/rules.d/50-udev.rules
> KERNEL="agpgart", NAME="misc/%k", SYMLINK+="%k"
>
> However, on boot, no symlink exists (although the /dev/misc/agpgart
> device is properly created).
>
> Once booted, the symlink does exist in the udev database:
> # udevadm info --export-db | grep -A 8 'P: /devices/virtual/misc/agpgart'
> P: /devices/virtual/misc/agpgart
> N: misc/agpgart
> S: agpgart
> E: UDEV_LOG=3
> E: DEVPATH=/devices/virtual/misc/agpgart
> E: MAJOR\x10
> E: MINOR\x175
> E: DEVNAME=/dev/misc/agpgart
> E: DEVLINKS=/dev/agpgart
>
> I don't quite know how to interpret the results from udevtest, but the
> results are here:
> http://dellin.net/static/temp/udevtest_output.txt
>
> A few other notes:
>  - The system is running a recent copy of Gentoo Linux.
>  - This started happening when I upgraded my kernel from 2.6.29.5 to 2.6.31.6.
>  - The /dev/video0 symlink has the same problem; it should be linked
> to /dev/v4l/video0, which is created correctly.
>
> Any ideas?

You should not swap kernel node names with symlink names. The primary
name in /dev should always match the name in /sys. In general, on
recent kernels, almost all rules with NAME= should be removed and the
kernel-provided names not be overwritten by userspace config, and only
symlinks (which do no clash with kernel names) added.

Kay

Re: Failed to Create Symlinks ...

[Matthias Schwarzott]

On Sonntag, 29. November 2009, Kay Sievers wrote:
> On Sat, Nov 28, 2009 at 23:52, Chris Dellin <cdellin@gmail.com> wrote:
> > I'm having some trouble recently with my installation of udev.  I
> > expect it to create symlinks for a few devices, but no symlinks are
> > created.  For example:
> >
> > udev should create a symlink, as per the rule below:
> > $ grep agpgart /etc/udev/rules.d/50-udev.rules
> > KERNEL="agpgart", NAME="misc/%k", SYMLINK+="%k"
> >
> > However, on boot, no symlink exists (although the /dev/misc/agpgart
> > device is properly created).
> >
> > Once booted, the symlink does exist in the udev database:
> > # udevadm info --export-db | grep -A 8 'P: /devices/virtual/misc/agpgart'
> > P: /devices/virtual/misc/agpgart
> > N: misc/agpgart
> > S: agpgart
> > E: UDEV_LOG=3
> > E: DEVPATH=/devices/virtual/misc/agpgart
> > E: MAJOR\x10
> > E: MINOR\x175
> > E: DEVNAME=/dev/misc/agpgart
> > E: DEVLINKS=/dev/agpgart
> >
> > I don't quite know how to interpret the results from udevtest, but the
> > results are here:
> > http://dellin.net/static/temp/udevtest_output.txt
> >
> > A few other notes:
> >  - The system is running a recent copy of Gentoo Linux.
> >  - This started happening when I upgraded my kernel from 2.6.29.5 to
> > 2.6.31.6. - The /dev/video0 symlink has the same problem; it should be
> > linked to /dev/v4l/video0, which is created correctly.
> >
> > Any ideas?
>
> You should not swap kernel node names with symlink names. The primary
> name in /dev should always match the name in /sys. In general, on
> recent kernels, almost all rules with NAME= should be removed and the
> kernel-provided names not be overwritten by userspace config, and only
> symlinks (which do no clash with kernel names) added.
>
I have a similar issue.
the lvm2 package on gentoo installs this udev rule:
KERNEL="device-mapper", SYMLINK+="mapper/control"

Now udev-147 cries about not being able to create the symlink as 
kernel-provided name is already set to "mapper/control".

So is the only possibility to surpress this warning to adjust the rule to 
this?
KERNEL="device-mapper", NAME="mapper/control"

Matthias

Re: Failed to Create Symlinks ...

[Kay Sievers]

On Sun, Nov 29, 2009 at 20:15, Matthias Schwarzott <zzam@gentoo.org> wrote:
> I have a similar issue.
> the lvm2 package on gentoo installs this udev rule:
> KERNEL="device-mapper", SYMLINK+="mapper/control"
>
> Now udev-147 cries about not being able to create the symlink as
> kernel-provided name is already set to "mapper/control".

Yes, this is expected, mapper/control is the primary name, and not a symlink.

> So is the only possibility to surpress this warning to adjust the rule to
> this?
> KERNEL="device-mapper", NAME="mapper/control"

Looks like, yes. Recent kernels/udev though should not have any rule
for this. We removed all such rules from the udev default rule set.

Kay

Re: Failed to Create Symlinks ...

[Kay Sievers]

On Mon, Nov 30, 2009 at 00:35, Chris Dellin <cdellin@gmail.com> wrote:
> On Sun, Nov 29, 2009 at 14:04, Kay Sievers <kay.sievers@vrfy.org> wrote:

>> You should not swap kernel node names with symlink names. The primary
>> name in /dev should always match the name in /sys. In general, on
>> recent kernels, almost all rules with NAME= should be removed and the
>> kernel-provided names not be overwritten by userspace config, and only
>> symlinks (which do no clash with kernel names) added.
>
> OK; in this case, the path in /sys is
> /sys/devices/virtual/misc/agpgart, while the "kernel name" is
> "agpgart".  So the primary /dev device should just be /dev/agpgart
> (and not /dev/misc/agpgart).

Yes, or the kernel would need to provide that name. But I doubt that
/dev/misc/ makes much sense.

> Does this mean that the documentation examples, such as this:
>   KERNEL="hdb", NAME="my_spare_disk"
> should be replaced with:
>   KERNEL="hdb", SYMLINK+="my_spare_disk" ?

Sure, kernel names should not be changed, it's almost always wrong to do that.

> Does this mean that use of NAME should be discouraged outright?  In
> that case, I'll file this as a bug with Gentoo, as these are all
> distribution-default rules.

Yes, NAME= should be a rare exception with a very good reason. Like in
case that the kernel misses the right name, like for older kernels, or
not well-maintained drivers, or in case network interfaces are
renamed.

Thanks,
Kay

Re: Failed to Create Symlinks ...

[Matthias Schwarzott]

On Sonntag, 29. November 2009, Kay Sievers wrote:
> On Sun, Nov 29, 2009 at 20:15, Matthias Schwarzott <zzam@gentoo.org> wrote:
> > I have a similar issue.
> > the lvm2 package on gentoo installs this udev rule:
> > KERNEL="device-mapper", SYMLINK+="mapper/control"
> >
> > Now udev-147 cries about not being able to create the symlink as
> > kernel-provided name is already set to "mapper/control".
>
> Yes, this is expected, mapper/control is the primary name, and not a
> symlink.
I suggested lvm2 maintainers to change the rule to
KERNEL="device-mapper", NAME="mapper/control"

>
> > So is the only possibility to surpress this warning to adjust the rule to
> > this?
> > KERNEL="device-mapper", NAME="mapper/control"
>
> Looks like, yes. Recent kernels/udev though should not have any rule
> for this. We removed all such rules from the udev default rule set.
>
Sure, but gentoo does aim to support at least not only the newest kernels, but 
udev for now still supports 2.6.27 or even older versions with older udev 
versions.

Is there a way to conditionalize these rules besides shell tricks at boot 
checking kernel versions and discarding some rules/rule files on some 
conditions.

Matthias

Re: Failed to Create Symlinks ...

[Matthias Schwarzott]

On Samstag, 28. November 2009, Chris Dellin wrote:
> Hey all,
>
> I'm having some trouble recently with my installation of udev.  I
> expect it to create symlinks for a few devices, but no symlinks are
> created.  For example:
>
> udev should create a symlink, as per the rule below:
> $ grep agpgart /etc/udev/rules.d/50-udev.rules
> KERNEL="agpgart", NAME="misc/%k", SYMLINK+="%k"
>

>
> A few other notes:
>  - The system is running a recent copy of Gentoo Linux.
What is the version of udev you are running?
Unstable udev and latest two stable versions do not contain that rule you 
mentioned above.


Matthias

Re: Failed to Create Symlinks ...

[Kay Sievers]

On Mon, Nov 30, 2009 at 15:03, Matthias Schwarzott <zzam@gentoo.org> wrote:
> On Sonntag, 29. November 2009, Kay Sievers wrote:
>> On Sun, Nov 29, 2009 at 20:15, Matthias Schwarzott <zzam@gentoo.org> wrote:
>> > I have a similar issue.
>> > the lvm2 package on gentoo installs this udev rule:
>> > KERNEL="device-mapper", SYMLINK+="mapper/control"
>> >
>> > Now udev-147 cries about not being able to create the symlink as
>> > kernel-provided name is already set to "mapper/control".
>>
>> Yes, this is expected, mapper/control is the primary name, and not a
>> symlink.
> I suggested lvm2 maintainers to change the rule to
> KERNEL="device-mapper", NAME="mapper/control"
>
>>
>> > So is the only possibility to surpress this warning to adjust the rule to
>> > this?
>> > KERNEL="device-mapper", NAME="mapper/control"
>>
>> Looks like, yes. Recent kernels/udev though should not have any rule
>> for this. We removed all such rules from the udev default rule set.
>>
> Sure, but gentoo does aim to support at least not only the newest kernels, but
> udev for now still supports 2.6.27 or even older versions with older udev
> versions.
>
> Is there a way to conditionalize these rules besides shell tricks at boot
> checking kernel versions and discarding some rules/rule files on some
> conditions.

Just do not try to swap kernel names with symlink names. There should
be no problem having rules with NAME= as long as they match the
standard kernel name.

Kay