Setting Up a Network Scanner on Linux
I have used my network scanner through Windows for a long time. It works well except I need to get a Windows laptop. Although the default storage path of the scanner resides in a samba server, it is still tedious to do daily scan. I managed to set it up on Linux. This blog is for my reference.
Device and system
The scanner is Canon MF113w. The OS of my desktop is Arch Linux. Home network is managed by OpenWrt.
Basic setup
Linux uses SANE to communicate with scanners. Install sane as a backend and simple-scan as a frontend utility.
sudo pacman -Sy sane simple-scan |
According to the README of sane-airscan, Canon MF110/910 can only work in eSCL mode. The man page of sane-escl states that “eSCL devices that announce themselves on mDNS as _uscan.utcp or _uscans._utcp. If the device is available, the sane-escl backend recovers these capacities”.
man 5 sane-escl |
In order to use Avahi for multicastDNS service discovery, I choose to install avahi package. First the mutlicastDNS of systemd should be disabled to avoid conflict.
Read the man page of systemd-resolved
man 5 resolved.conf |
and set MulticastDNS=no in /etc/systemd/resolved.conf, then restart systemd-resolved service.
sudo systemctl restart systemd-resolved |
Install avahi nss-mdns:
sudo pacman -S avahi nss-mdns |
Then set hosts entry of /etc/nsswitch.conf with the value:
hosts: files mymachines resolve [!UNAVAIL=continue] myhostname dns mdns [NOTFOUND=return] |
Start the avahi-daemon service:
sudo systemctl enable --now avahi-daemon.service |
The avahi-daemon.service can be triggered by avahi-daemon.socket. So enable the socket and disable the service could be a better practice.
Trouble shooting
The sane package on Arch Linux contains a cli tool scanimage. After the basic setup, scanimage -L should list the scanner. However I encountered some problems.
Custom TLD
I used .home as TLD instead of .local in home network. To deal with the TLD, /etc/nsswitch.conf used mdns instead of mdns_minimal because the mdns_minimal module handles queries for the .local TLD only.
Since .home is configured as the domain for LAN network, I set domain-name=home in /etc/avahi/avahi-daemon.conf. This is the root cause of the problem that avahi can’t discover service.
Whenavahi-browse --all --ignore-local --resolve --terminate was running to list services, I monitored the mdns traffic by wireshark
sudo tshark -i enp176s0 -f "udp port 5353" |
During this process, avahi-browse still got no outputs. But I got a reponse from wireshark:
1493 10840.052424716 10.0.7.76 → 224.0.0.251 MDNS 124 Standard query 0x0000 PTR _companion-link._tcp.local, "QM" question PTR _rdlink._tcp.local, "QM"
question PTR _sleep-proxy._udp.local, "QM" question`
MDNS 394 Standard query response 0x0000 PTR amzn.dmgr:*:*:612333._amzn-wplay._tcp.local PTR amzn.dmgr:*:*:612333._amzn-wplay._tcp.local SRV, cache flush 0 0 39474 amazon-*-home.local TXT, cache flush`
As we can see, it is a response of mDNS query from `amazon-*-home.local`. Pay attention to the "-home.local" part. As "home" is the domain of LAN network, the hostname should be `amazon-*.home
It’s a mDNS multicast message from an amazon device. The hostname of this device has a .local suffix.
So, I checked the host name, avahi-resolve-host-name amazon-*-home.local and got the right ip:
amazon-*-home.local 10.0.7.85 |
But I can’t ping this hostname:
ping amazon-*-home.local |
or try this:
ping amazon-*-home |
This amazon device added “-home” to its hostname, and used “.local” as its TLD.
However, I can do this:
ping amazon-* |
or
ping amazon-*.home |
So, even .home is the domain of the home network, the avahi service of devices may be hard coded to use .local. This should be the root of all these quirks.
I commented out domain-name=home in /etc/avahi/avahi-daemon.conf, reverted back to the default domain-name=local. And, avahi-browse --all --ignore-local --resolve --terminate gets all the services.
Intermittent connection failure
The scanner is set static IPv4 and IPv6 with DHCP through its console. Sometimes when I start simple-scan, I get errors that simple-scan cannot connect to the scanner. Running scanimage -L can see the scanner is online with its IPv4 address. However, if I run scanimage -L again, the scanner is listed with its IPv6 address.
This dual stack IP addresses cause the connection problem between simple-scan and the scanner. simple-scan works well after I disabled IPv6 through the console of the scanner.
Speed up scanner discovery
There are many backends list in the /etc/sane.d/dll.conf file. For my eSCL scanner, commenting out all lines of this file except escl can speed up the scanner discovery process.