saned: io/hpmud/musb.c 2101: usb_open inválido: permissão negada

Tentei configurar um scanner de rede com SANE seguindo este tutorial: Sane Daemon Tutorial

Mas se eu tentar adicionar o scanner em um cliente, ele não funciona como costuras sanadas para não ter acesso à porta USB.

Feb  9 18:55:47 druckserver systemd[1]: Started Scanner Service  (10.1.20.25:50515).
Feb  9 18:55:47 druckserver saned[2005]: saned (AF-indep+IPv6+systemd) from sane-backends 1.0.27 starting up
Feb  9 18:55:47 druckserver saned[2005]: check_host: access by remote host: ::ffff:10.1.20.25
Feb  9 18:55:47 druckserver systemd-resolved[1172]: Using degraded feature set (UDP) for DNS server 10.1.10.1.
Feb  9 18:55:52 druckserver saned[2005]: init: access granted to User@::ffff:10.1.20.25
Feb  9 18:55:57 druckserver saned[2005]: io/hpmud/musb.c 2101: Invalid usb_open: Permission denied
Feb  9 18:55:57 druckserver saned[2005]: message repeated 3 times: [ io/hpmud/musb.c 2101: Invalid usb_open: Permission denied]
Feb  9 18:55:57 druckserver saned[2005]: saned exiting
Feb  9 18:56:35 druckserver systemd[1]: Started Scanner Service (10.1.20.25:50531).
Feb  9 18:56:35 druckserver saned[2013]: saned (AF-indep+IPv6+systemd) from sane-backends 1.0.27 starting up
Feb  9 18:56:35 druckserver saned[2013]: check_host: access by remote host: ::ffff:10.1.20.25
Feb  9 18:56:35 druckserver saned[2013]: init: access granted to User@::ffff:10.1.20.25
Feb  9 18:56:41 druckserver saned[2013]: io/hpmud/musb.c 2101: Invalid usb_open: Permission denied
Feb  9 18:56:41 druckserver saned[2013]: message repeated 3 times: [ io/hpmud/musb.c 2101: Invalid usb_open: Permission denied]
Feb  9 18:56:41 druckserver saned[2013]: saned exiting

O que aparece deste syslog é esta linha:

Feb  9 18:56:41 druckserver saned[2013]: io/hpmud/musb.c 2101: Invalid usb_open: Permission denied

Eu não tenho absolutamente nenhuma idéia de como consertar isso. Preciso adicionar o usuário "sane" a um grupo específico?

Obrigado por qualquer ajuda.