Setting up and administering a scanner connected to a USB port.
Scanning a document from a standalone scanner or one in a multifunctional device involves using SANE (Scanner Access Now Easy). The Project provides a collection of scanner backends which can communicate with the scanner in order to drive it. Backends not provided by SANE can easily be accomodated within the SANE scanning framework whether or not the software is free (HP) or non-free (Brother, Samsung etc). Those scanners which SANE directly supports are listed here
The first step on the road to successful scanning is to install libsane, which has the central library for operating scanners. The package also provides SANE's collection of scanner backends. If the scanner is not supported by SANE, the backend (and other files) will have to be obtained from the Debian archives or the vendor. A notable free backend source requiring this step is the one for the all-in-one machines from HP.
The next two sections assume you have the backend (and other files) that SANE or the vendor supply. Your scanner should work out-of the-box with a frontend without bothering with any of the next steps, but it is as well to be aware there are trouble-shooting procedures which can be followed. The SANE manual lists the backends available.Each backend has its own manual page and a configuration file in etc/sane.d
Scanner and Backend Discovery
Connect the scanner to the computer and see what lsusb gives:
brian@desktop:~$ lsusb Bus 002 Device 005: ID 04b8:080f Seiko Epson Corp. Stylus Photo RX420/RX425/RX430
There is an Epson Stylus Photo on USB Bus 002 and at Device 005. That's fine, but it tells us nothing about whether we can get the device scanning.
Hopefully, you will see your scanner found.
brian@test:~$ sane-find-scanner # sane-find-scanner will now attempt to detect your scanner. If the # result is different from what you expected, first make sure your # scanner is powered up and properly connected to your computer. # No SCSI scanners found. If you expected something different, make sure that # you have loaded a kernel SCSI driver for your SCSI adapter. could not open USB device 0x0644/0x0200 at 004:002: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0002 at 004:001: Access denied (insufficient permissions) could not open USB device 0x045e/0x008c at 007:002: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0001 at 007:001: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0001 at 006:001: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0001 at 005:001: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0002 at 003:001: Access denied (insufficient permissions) found USB scanner (vendor=0x04b8 [EPSON], product=0x080f [USB MFP]) at libusb:002:005 could not open USB device 0x1d6b/0x0001 at 002:001: Access denied (insufficient permissions) could not open USB device 0x04b3/0x3003 at 001:005: Access denied (insufficient permissions) could not open USB device 0x04b3/0x3004 at 001:004: Access denied (insufficient permissions) could not open USB device 0x1d6b/0x0001 at 001:001: Access denied (insufficient permissions) # Your USB scanner was (probably) detected. It may or may not be supported by # SANE. Try scanimage -L and read the backend's manpage.
A scanner has correctly been located on Bus 002 as Device 005. If access to this device had also been denied (as was access to the other USB devices) the permissions on the USB bus would have had to be looked at.
Now it is known that a USB scanner exists, run
The output obtained here is:
device `epson:libusb:002:005' is a Epson RX420 flatbed scanner
The scanimage manual describes what -L is intended to do. In the context of a local USB device, the positive response indicates that SANE has a backend to support the scanner.
Now place a document on the scanner's glass plate and scan it with
scanimage > image.pnm
It is not necessary for a locally logged-in user to be in the scanner group. Permissions on the scanner device are automatically taken care of by the kernel and those on the USB bus are granted to a user by udev, given that
- libpam-systemd is installed.
There is an appropriate vendor *.rules file in /lib/udev/rules.d.
A user wishing to access and use a scanner must have permission to access a scanner device file and to use a device on the USB bus. Under Debian's default init system,systemd, and with libpam-systemd installed, the correct permissions are set up by /lib/udev/rules.d/60-libsane.rules when the scanner is plugged in.
For the scanner device file:
brian@test:~$ ls -l /dev/sg* crw------- 1 root root 21, 0 Aug 4 09:40 /dev/sg0 crw-rw----+ 1 root root 21, 1 Aug 4 09:40 /dev/sg1 crw------- 1 root root 21, 2 Aug 4 09:40 /dev/sg2 crw------- 1 root root 21, 3 Aug 4 09:40 /dev/sg3 crw------- 1 root root 21, 4 Aug 4 09:40 /dev/sg4 crw------- 1 root root 21, 5 Aug 4 09:40 /dev/sg5 crw------- 1 root root 21, 6 Aug 4 09:40 /dev/sg6 crw------- 1 root root 21, 7 Aug 4 14:46 /dev/sg7
Observe the + after the Unix permissions for /dev/sg1. It indicates an ACL (Access Control List), which specifies which users are granted access to/dev/sg1. To see an ACL, do
brian@test:~$ getfacl /dev/sg1 getfacl: Removing leading '/' from absolute path names # file: dev/sg1 # owner: root # group: root user::rw- user:brian:rw- group::--- mask::rw- other::---
User brian has rw access to the device file. Similar permissions would be required on the USB bus.
For the USB bus:
brian@test:~$ ls -l /dev/bus/usb/*/* crw------- 1 root root 189, 0 Aug 4 09:40 /dev/bus/usb/001/001 crw------- 1 root root 189, 3 Aug 4 13:40 /dev/bus/usb/001/004 crw------- 1 root root 189, 4 Aug 4 13:40 /dev/bus/usb/001/005 crw------- 1 root root 189, 128 Aug 4 09:40 /dev/bus/usb/002/001 crw-rw----+ 1 root root 189, 132 Aug 4 18:25 /dev/bus/usb/002/005 crw------- 1 root root 189, 256 Aug 4 09:40 /dev/bus/usb/003/001 crw------- 1 root root 189, 384 Aug 4 09:40 /dev/bus/usb/004/001 crw------- 1 root root 189, 385 Aug 4 09:40 /dev/bus/usb/004/002 crw------- 1 root root 189, 512 Aug 4 09:40 /dev/bus/usb/005/001 crw------- 1 root root 189, 640 Aug 4 09:40 /dev/bus/usb/006/001 crw------- 1 root root 189, 768 Aug 4 09:40 /dev/bus/usb/007/001 crw------- 1 root root 189, 769 Aug 4 09:40 /dev/bus/usb/007/002 brian@test:~$ getfacl /dev/bus/usb/002/005 getfacl: Removing leading '/' from absolute path names # file: dev/bus/usb/002/005 # owner: root # group: root user::rw- user:brian:rw- group::--- group:scanner:rw- mask::rw- other::---
User brian could also gain access to the USB device by being in the scanner group. But there is little point in doing that unless brian is expected to log in from a remote location with ssh etc.
Configuration Files for libsane
libsane-common installs the configuration files dll.conf, dll.d, net.conf and saned.conf in /etc/sane.d. The first, third and fourth files are important for sharing and accessing a scanner over the network.
The content of dll.conf is a list of backends that may be loaded dynamically upon demand. Commenting out the backends not used might lead to a slight decrease in scanning time. It is also possible to add a file in /etc/sane.d/dll.d that contains a list of backends to be added. This is often done by software providing a non-SANE backend.
HP all-in-one (aio) Machines
A backend for these devices is developed and supported by HP via HPLIP. The backend is named hpaio and is listed in the file hplip in /etc/saned/dll.d. Device detection support is provided by /lib/udev/rules.d/56-hpmud.rules. The straightforward way to employ hpaio and 56-hpmud.rules is to install hplip and its recommended dependencies. This way also makes it easier to install a non-free plugin with hp-plugin if the scanner needs one.
As a matter of interest, all that is really needed for scanning with an aio scanner is libsane-hpaio (without its recommended packages) and 56-hpmud.rules. Copy the latter file to /lib/udev/rules.d/ from the hplip package.
Scanning over WiFi with AirPrint / eSCL scanners
Except for aforementioned HP scanners, most AirPrint / eSCL scanners are currently (as of 2017) not supported by Sane. But since the protocol is a simple XML and HTTP based protocol, the rudimentary (command line) python script https://github.com/kno10/python-scan-eSCL can be used to scan with such devices. As this may be the preferred way to support Mac OS X, it may become increasingly common.
Example devices that work with this include: Canon PIXMA TS5050 (and probably other Canon PIXMA TS models), and according to sane-devel it can be modified to also support Kyocera and HP. But of course it would be best if someone added a eSCL/AirPrint driver to SANE, so you can use all GUIs.
Frontends for Scanning
A frontend is a program which interfaces with a SANE backend to produce a scanned output in a desired format. SANE has been designed to interwork with any SANE-compliant frontend, command line or GUI based
scanimage: A command line interface from the SANE Project to control scanning.
xscanimage: A SANE Project GUI for image acquisition from a scanner. Can be invoked through The GIMP.
gscan2pdf: A graphical application to produce PDFs or DjVus from scanned documents.
Installation Notes for Various Scanners
Sharing a scanner over the network.
Do not forget to read the Debian and other documentation in /usr/share/doc/libsane. Hopefully, there is no conflict between it and what is on this page.