sane does not work as saned but as root it does

Question

I have a plug computer that I want to use as scanner server using sane. It already worked with a different plug, so I know for sure that the scanner and sane are workable together.

If I issue scanimage -L as root I get this output:

device `hpaio:/usb/Deskjet_F300_series?serial=CN73CGJ05504KH' is a Hewlett-Packard Deskjet_F300_series all-in-one

which is what I am expecting, but when I call the command as saned I get this output:

No scanners were identified. [...]

If I call sane-find-scanner as saned it brings up:

found USB scanner (vendor=0x03f0, product=0x5511) at libusb:001:015

Now the interesting part is that the vendor and product is not detected here, but when I do the same as root this is the result:

found USB scanner (vendor=0x03f0 [HP], product=0x5511 [Deskjet F300 series]) at libusb:001:015

So, somehow the root user has access to the list of vendors (and thus is able to detect the scanner) while saned is not. I don't want to run the saned server as root so I need to figure this out.

All settings I did in saned.conf are for the network interaction, but my problem is on the local host, so I skip the config file (but of course can provide it if necessary)

saned groups: saned scanner

I assume that I need to change the privileges of the file where vendor and product are mapped (/etc/sane.d/hp.conf), but that is already readable by sane.

-rw-r--r-- 1 saned scanner 396 Dec 12  2010 hp3900.conf
-rw-r--r-- 1 saned scanner  76 Dec 12  2010 hp4200.conf
-rw-r--r-- 1 saned scanner 238 Dec 12  2010 hp5400.conf
-rw-r--r-- 1 saned scanner 497 Dec 12  2010 hp.conf
-rw-r--r-- 1 saned scanner  22 Dec 12  2010 hpsj5s.conf

Same for /etc/sane.d/dll.d/

-rw-r--r-- 1 saned scanner   38 Dec 10  2013 hplip

Interesting is that neither of these files contain the Deskjet_F300_series information, so maybe there is another file?

Also, while the scanner does have a printing option, I'm not interested in this.

I did read this post, but I would prefer not to do what is described there, because somewhere the information is already present and I would like to access that place, from the saned user.

Answer 1

I found that the scanimage -L works after I added saned to the group lp, moments after I posted the question.

I still am interested in the proper answer to this question (where does the information come from). So, this answer is for future visitors who just want to have it fixed.