Auto-handling arbitrary USB mass storage devices

Auto-handling arbitrary USB mass storage devices

[Jason LeBrun]

I'd like to use udev/hotplug to automate the addition/removal of USB storage 
devices. I'm not sure of the best way to go about this, since these tools 
certainly provide more than one way to do it!

Basically, I'd like to set things up once, and then have this to happen for 
any plugged usb-storage device:

1. When I plug in a device, a device node with a some friendly name, like the 
results of SYSFS{vendor} should get created in /dev. 

2. Mount points should get automatically created somewhere, like in /mnt 
or /media. They should also have a similarly nice name. 

3. A line should be added to fstab that corresponds to the new drive.

4. Optionally, the drive should be mounted right away.

It *seems* like hotplug/udev should allow this to be easy, but here are the 
problems I'm having in each step:

1. I can't seem to use all of the SYSFS attributes. For example, 
SYSFS{product} won't return anything. 

Furthermore, the %s format specifier is not working quite properly. For 
example, I have an external USB HD with two partitions. If I use 
SYMLINK="%s{vendor}%n" in my rules file, I get in my /dev directory the 
following:
lrwxrwxrwx   1 root  root         4 Sep 21 18:34 1 -> sda1
lrwxrwxrwx   1 root  root         4 Sep 21 18:34 2 -> sda2
lrwxrwxrwx   1 root  root         4 Sep 21 18:34 WDC -> sda1

If I just use a hard coded version, SYMLINK="WDC%n", it comes up properly:
lrwxrwxrwx   1 root  root         4 Sep 21 18:36 WDC1 -> sda1
lrwxrwxrwx   1 root  root         4 Sep 21 18:36 WDC2 -> sda2



2+3. I want to create mount points and fstab entries based on either a 
"friendly" SYSFS attribute, or the device link created in step 1. It seems to 
be that everything beyond step 1 should be done using the hotplug system. I 
have no idea how to get the information I need for my hotplug scripts, 
however. Is there any way for hotplug to get the info that it needs from 
udev? 

Also, I can't seem to get the REMOVE actions to do anything in either udev or 
hotplug. 


Any hints or suggestions for any of the above would be greatly appreciated! 

Thanks,

Jason


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Re: Auto-handling arbitrary USB mass storage devices

[Greg KH]

On Tue, Sep 21, 2004 at 06:43:23PM -0700, Jason LeBrun wrote:
> I'd like to use udev/hotplug to automate the addition/removal of USB storage 
> devices. I'm not sure of the best way to go about this, since these tools 
> certainly provide more than one way to do it!
> 
> Basically, I'd like to set things up once, and then have this to happen for 
> any plugged usb-storage device:
> 
> 1. When I plug in a device, a device node with a some friendly name, like the 
> results of SYSFS{vendor} should get created in /dev. 

udev can do this for you.

> 2. Mount points should get automatically created somewhere, like in /mnt 
> or /media. They should also have a similarly nice name. 
> 
> 3. A line should be added to fstab that corresponds to the new drive.
> 
> 4. Optionally, the drive should be mounted right away.

HAL does these steps for you.  Not udev.

> It *seems* like hotplug/udev should allow this to be easy, but here are the 
> problems I'm having in each step:
> 
> 1. I can't seem to use all of the SYSFS attributes. For example, 
> SYSFS{product} won't return anything. 

What is the full rule you are trying to match on?

> Furthermore, the %s format specifier is not working quite properly. For 
> example, I have an external USB HD with two partitions. If I use 
> SYMLINK="%s{vendor}%n" in my rules file, I get in my /dev directory the 
> following:
> lrwxrwxrwx   1 root  root         4 Sep 21 18:34 1 -> sda1
> lrwxrwxrwx   1 root  root         4 Sep 21 18:34 2 -> sda2
> lrwxrwxrwx   1 root  root         4 Sep 21 18:34 WDC -> sda1

Please realize that depending on the level in sysfs where your rule
matches, there might not be a vendor file there.  That's what is
probably happening here.

thanks,

greg k-h


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