On Mon 27 Jul 2020 at 19:39:25 +0200, Nicolas George wrote: > Nicolas George (12020-07-27): > > Well, in between explaining why all the answers I got do not match the > > question, I RTFS, and it seems indeed it is not possible with SANE. What > > stupid design. > > > > As for the hpaio backend, it relies on CUPS to find networked printers, > > but CUPS will not be always running. What stupid design. > > These are now: > > https://gitlab.com/sane-project/frontends/-/issues/18 > https://bugs.launchpad.net/hplip/+bug/1889109 > > I predict that SANE will blame hpaio and hpaio will not care that people > do not want to run CUPS needlessly.
The assertion is: libsane-hpaio relies on CUPS to detect networked all-in-one scanner-printers. That means that if CUPS is not running, networked devices are usable by specifying the URL, but they will not be detected. We may test this assertion as follows: 1. Install Debian with the base system only. 2. apt install libsane avahi-daemon. 3. brian@t5730sid:~$ scanimage -L No scanners were identified. If you were expecting something different, check that the scanner is plugged in, turned on and detected by the sane-find-scanner tool (if appropriate). Please read the documentation which came with this software (README, FAQ, manpages). brian@t5730sid:~$ 4. brian@t5730sid:~$ dpkg -l | grep cups brian@t5730sid:~$ 5. apt install libsane-hpaio --no-install-recommends 6. brian@t5730sid:~$ dpkg -l | grep cups ii libcups2:i386 2.2.10-6+deb10u1 brian@t5730sid:~$ 7. brian@t5730sid:~$ scanimage -L device `hpaio:/net/envy_4500_series?ip=192.168.7.235&queue=false' is a Hewlett-Packard envy_4500_series all-in-one brian@t5730sid:~$ Contending that libsane-hpaio relies on CUPS to detect scanners appears to be based on a misunderdstanding of the code in hpaio.c. Most people would take CUPS to mean 'apt install cups' and, as we see, cups-daemon is not running. Game, set and match. -- Brian.