No puedo hacer funcionar el escáner de la impresora EPSON XP-201

open a terminal (ctrl-alt-t) and issue the commands

uname -a
lsb_release -a
lsusb
dpkg -l | grep iscan
sane-find-scanner

then select all output, copy it and paste into this question document.

horacio@horacio-M68MT-S2:~$ uname-a
uname-a: no se encontró la orden
horacio@horacio-M68MT-S2:~$ -lsb_release un
No se ha encontrado la orden «-lsb_release», quizás quiso decir:
 La orden «lsb_release» del paquete «lsb-release» (main)
-lsb_release: no se encontró la orden
horacio@horacio-M68MT-S2:~$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 0458:707b KYE Systems Corp. (Mouse Systems)
Bus 001 Device 004: ID 058f:6364 Alcor Micro Corp. Hi-Speed 7-in-1 Flash Card Reader/Writer [Sabrent]
Bus 002 Device 002: ID 0458:00ae KYE Systems Corp. (Mouse Systems)
Bus 001 Device 005: ID 04b8:0896 Seiko Epson Corp.
horacio@horacio-M68MT-S2:~$ dpkg-l|grep iScan
dpkg-l: no se encontró la orden
horacio@horacio-M68MT-S2:~$ 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.

found USB scanner (vendor=0x04b8, product=0x0896) at libusb:001:005
  # Your USB scanner was (probably) detected. It may or may not be supported by
  # SANE. Try scanimage -L and read the backend's manpage.

  # Not checking for parallel port scanners.

  # Most Scanners connected to the parallel port or other proprietary ports
  # can't be detected by this program.

  # You may want to run this program as root to find all devices. Once you
  # found the scanner devices, be sure to adjust access permissions as
  # necessary.

No has copiado correctamente las órdenes que te ha pedido Manfred, alguna de las cuales era para confirmar la versión de Ubuntu que tienes instalada. Por favor, repítelo y te aconsejo que copies y pegues directamente las órdenes del texto del comentario.

Los drivers que has bajado son la versión de 64 bits (elnombre de los paquetes es confuso, porque aunque ponga "amd64" no quiere decir que sean únicamente para procesadores AMD, sino simplemente que es la versión de 64 bits). Si tienes instalada la versión de 32 bits tendrías que descargar los drivers de Epson también de 32 bits ('x86").

José Luis, ¡muchas gracias por el consejo y perdón por mi ineptitud!: sé tanto de Linux como de lengua armenia. A pesar de que uso Ubuntu desde la versión 8.04 siempre he tenido que trapichear un poco solo cuando el sistema no me reconoce el escáner.

Aquí está lo que me solicitó Manfred:

horacio@horacio-M68MT-S2:~$ uname -a
Linux horacio-M68MT-S2 3.2.0-56-generic #86-Ubuntu SMP Wed Oct 23 09:20:45 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
horacio@horacio-M68MT-S2:~$ lsb_release -a
LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:cxx-3.0-amd64:cxx-3.0-noarch:cxx-3.1-amd64:cxx-3.1-noarch:cxx-3.2-amd64:cxx-3.2-noarch:cxx-4.0-amd64:cxx-4.0-noarch:desktop-3.1-amd64:desktop-3.1-noarch:desktop-3.2-amd64:desktop-3.2-noarch:desktop-4.0-amd64:desktop-4.0-noarch:graphics-2.0-amd64:graphics-2.0-noarch:graphics-3.0-amd64:graphics-3.0-noarch:graphics-3.1-amd64:graphics-3.1-noarch:graphics-3.2-amd64:graphics-3.2-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-3.2-amd64:printing-3.2-noarch:printing-4.0-amd64:printing-4.0-noarch:qt4-3.1-amd64:qt4-3.1-noarch
Distributor ID: Ubuntu
Description: Ubuntu 12.04.3 LTS
Release: 12.04
Codename: precise
horacio@horacio-M68MT-S2:~$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 0458:707b KYE Systems Corp. (Mouse Systems)
Bus 001 Device 004: ID 058f:6364 Alcor Micro Corp. Hi-Speed 7-in-1 Flash Card Reader/Writer [Sabrent]
Bus 002 Device 002: ID 0458:00ae KYE Systems Corp. (Mouse Systems)
horacio@horacio-M68MT-S2:~$ dpkg -l | grep iscan
ii iscan 2.29.2-1~usb0.1.ltdl7 simple, easy to use scanner utility for EPSON scanners
ii iscan-data 1.13.0-1 Image Scan! for Linux data files
ii iscan-network-nt 1.1.0-2 Image Scan! Network Plugin
horacio@horacio-M68MT-S2:~$ 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.

  # No USB scanners found. If you expected something different, make sure that
  # you have loaded a kernel driver for your USB host controller and have setup
  # the USB system correctly. See man sane-usb for details.

  # Not checking for parallel port scanners.

  # Most Scanners connected to the parallel port or other proprietary ports
  # can't be detected by this program.

  # You may want to run this program as root to find all devices. Once you
  # found the scanner devices, be sure to adjust access permissions as
  # necessary.

Saludos cordiales.

Luego de publicar la entrada anterior me di cuenta de que tenía la impresora apagada. Aquí pongo la información referida al escáner que el sistema arroja, pero con la XP-201 encendida.

horacio@horacio-M68MT-S2:~$ 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.

found USB scanner (vendor=0x04b8, product=0x0896) at libusb:001:005
  # Your USB scanner was (probably) detected. It may or may not be supported by
  # SANE. Try scanimage -L and read the backend's manpage.

  # Not checking for parallel port scanners.

  # Most Scanners connected to the parallel port or other proprietary ports
  # can't be detected by this program.

  # You may want to run this program as root to find all devices. Once you
  # found the scanner devices, be sure to adjust access permissions as
  # necessary.

Saludos cordiales.

Según las instrucciones de Epson (http://download.ebz.epson.net/faq/linux/faq_ls_00002.html) para tu equipo tendrías que haber descargado e instalado los siguientes paquetes (y en este orden):
  - data package: iscan-data_1.24.0-2_all.deb (*)
  - core package: iscan_2.29.2-1~usb0.1.ltdl7_amd64.deb
  - network plugin package: iscan-network-nt_1.1.0-2_amd64.deb
Por lo que dices en tu mensaje inicial te falta el primero (*). Deinstala los dos que ya habías instalado y vuelve a instalar los tres. Luego ejecuta:
  scanimage -L
Y comprueba si te detecta ya el escáner.

José Luis, muchas gracias por tu ayuda. Estabas en lo cierto: me faltaba el primer paquete.

Hice lo que me indicaste y el escáner funcionó.

Un muy cordial saludo para vos.