udev RUN+=: device but no partitions

udev RUN+=: device but no partitions

[Dick Repasky]

If I use udev to run a script when a usb disk device appears, the device file
for the whole device is available in the script but device files for partitions
on the device are not.

Example: usb thumbdrive that appears as sdb and has one partition sdb1.

Udev entry

KERNEL="sdb", RUN+="/usr/local/sbin/check-sdb"

In check-sdb, if I run either "ls /dev/sdb*" or find /dev -name "sdb*", only
/dev/sdb appears but not /dev/sdb1.  Is that behavior correct?  When the same
script is run from the command-line, the partition device file appears.

My system is Ubuntu 8.04 (hardy) running udev-117-8.

Thanks,

Dick Repasky


-

Re: udev RUN+=: device but no partitions

[Matthew Dharm]

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I wonder if this could be a timing problem.  The disk is discovered before
it's partitions are discovered... if your script gets called in that time
window between the two, you would get the results you describe.

Matt

On Thu, Jun 05, 2008 at 06:35:05PM -0400, Dick Repasky wrote:
> 
> If I use udev to run a script when a usb disk device appears, the device file
> for the whole device is available in the script but device files for partitions
> on the device are not.
> 
> Example: usb thumbdrive that appears as sdb and has one partition sdb1.
> 
> Udev entry
> 
> KERNEL=="sdb", RUN+="/usr/local/sbin/check-sdb"
> 
> In check-sdb, if I run either "ls /dev/sdb*" or find /dev -name "sdb*", only
> /dev/sdb appears but not /dev/sdb1.  Is that behavior correct?  When the same
> script is run from the command-line, the partition device file appears.
> 
> My system is Ubuntu 8.04 (hardy) running udev-117-8.
> 
> Thanks,
> 
> Dick Repasky
> 
> 
> -
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-- 
Matthew Dharm                              Home: mdharm-usb@one-eyed-alien.net 
Maintainer, Linux USB Mass Storage Driver

Way to go, lava boy.
					-- Stef to Greg
User Friendly, 3/26/1998

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Re: udev RUN+=: device but no partitions

[Kay Sievers]

On Fri, Jun 6, 2008 at 12:35 AM, Dick Repasky <rrepasky@indiana.edu> wrote:
>
> If I use udev to run a script when a usb disk device appears, the device file
> for the whole device is available in the script but device files for partitions
> on the device are not.
>
> Example: usb thumbdrive that appears as sdb and has one partition sdb1.
>
> Udev entry
>
> KERNEL="sdb", RUN+="/usr/local/sbin/check-sdb"
>
> In check-sdb, if I run either "ls /dev/sdb*" or find /dev -name "sdb*", only
> /dev/sdb appears but not /dev/sdb1.  Is that behavior correct?  When the same
> script is run from the command-line, the partition device file appears.

You get separate events for the partitions, which you may want to hook
in, instead of expecting the partitions to be available when the disk
shows up.

In theory, the event for the disk is delayed until the partition table
is scanned and hte partitions are created. We changed that in the
kernel a while ago:
  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h‘d7e5dffc4844ef51fe11f497bd774c04413a00
Maybe that does not work for you for some reason.

Kay
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Re: udev RUN+=: device but no partitions

[Dick Repasky]

Thanks to you all.

I've skirted the problem by inserting a delay. If my script is called 
with no argument (as udev would call it) the script invokes itself in 
the background with a single argument and the re-invoked script sleeps 
for a second before doing anything. By the time that the script is 
finished napping, the partition device files are available.

Dick Repasky

Kay Sievers wrote:
> On Fri, Jun 6, 2008 at 12:35 AM, Dick Repasky <rrepasky@indiana.edu> wrote:
>> If I use udev to run a script when a usb disk device appears, the device file
>> for the whole device is available in the script but device files for partitions
>> on the device are not.
>>
>> Example: usb thumbdrive that appears as sdb and has one partition sdb1.
>>
>> Udev entry
>>
>> KERNEL="sdb", RUN+="/usr/local/sbin/check-sdb"
>>
>> In check-sdb, if I run either "ls /dev/sdb*" or find /dev -name "sdb*", only
>> /dev/sdb appears but not /dev/sdb1.  Is that behavior correct?  When the same
>> script is run from the command-line, the partition device file appears.
> 
> You get separate events for the partitions, which you may want to hook
> in, instead of expecting the partitions to be available when the disk
> shows up.
> 
> In theory, the event for the disk is delayed until the partition table
> is scanned and hte partitions are created. We changed that in the
> kernel a while ago:
>   http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;hÔd7e5dffc4844ef51fe11f497bd774c04413a00
> Maybe that does not work for you for some reason.
> 
> Kay

-- 

Dick Repasky
Center for Computational Cytomics
UITS Cubicle 101.08
Indiana University
USA

rrepasky@indiana.edu