No se puede ubicar el paquete libc6-dbg: i386 en la ventana acoplable

Estoy tratando de instalar libc6-dbg: i386 dentro de un contenedor docker basado en Ubuntu porque lo necesito para Valgrind, pero no puedo.

Dado el siguiente Dockerfile:

FROM ubuntu:14.04

MAINTAINER Me <[email protected]>

RUN apt-get update
RUN apt-get install libc6-dbg
RUN apt-get install libc6-dbg:i386

Ejecutando en un host Ubuntu 14.04 de escritorio de 64 bits:

sudo docker build .

Yo obtengo:

Step 0 : FROM ubuntu:14.04
 ---> 5506de2b643b
Step 1 : MAINTAINER Me <[email protected]>
 ---> Using cache
 ---> b1792911b80d
Step 2 : RUN apt-get update
 ---> Using cache
 ---> 5e3928c88aff
Step 3 : RUN apt-get install libc6-dbg
 ---> Running in ebd51fcb278b
Reading package lists...
Building dependency tree...
Reading state information...
The following NEW packages will be installed:
  libc6-dbg
0 upgraded, 1 newly installed, 0 to remove and 12 not upgraded.
Need to get 3452 kB of archives.
After this operation, 22.8 MB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu/ trusty-updates/main libc6-dbg amd64 2.19-0ubuntu6.3 [3452 kB]
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
debconf: unable to initialize frontend: Readline
debconf: (This frontend requires a controlling tty.)
debconf: falling back to frontend: Teletype
dpkg-preconfigure: unable to re-open stdin: 
Fetched 3452 kB in 0s (5325 kB/s)
Selecting previously unselected package libc6-dbg:amd64.
(Reading database ... 11527 files and directories currently installed.)
Preparing to unpack .../libc6-dbg_2.19-0ubuntu6.3_amd64.deb ...
Unpacking libc6-dbg:amd64 (2.19-0ubuntu6.3) ...
Setting up libc6-dbg:amd64 (2.19-0ubuntu6.3) ...
 ---> fe4bf0f008db
Removing intermediate container ebd51fcb278b
Step 4 : RUN apt-get install libc6-dbg:i386
 ---> Running in 460cab3c4631
Reading package lists...
Building dependency tree...
Reading state information...
E: Unable to locate package libc6-dbg
2014/11/20 15:23:06 The command [/bin/sh -c apt-get install libc6-dbg:i386] returned a non-zero code: 100

En el host puedo instalar libc6-dbg: i386, ¿por qué no puedo instalarlo dentro del contenedor docker?

Yo mismo responderé esto.

La información necesaria para resolver esto está en https://wiki.debian.org/Multiarch/HOWTO .

Apto en la imagen oficial de Docker ubuntu y también en phusion / baseimage está configurado solo con soporte para amd64. Esto es lo que te dice si preguntas:

# dpkg --print-architecture
amd64
# dpkg --print-foreign-architectures
<no output>

La forma de solucionar esto es agregar otra arquitectura antes de la actualización de apt-get :

# dpkg --add-architecture i386
# apt-get update
<lots of lines>
# apt-get install libc6-dbg:i386
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following extra packages will be installed:
  gcc-4.9-base:i386 libc6:i386 libgcc1:i386
Suggested packages:
  glibc-doc:i386 locales:i386
The following NEW packages will be installed:
  gcc-4.9-base:i386 libc6:i386 libc6-dbg:i386 libgcc1:i386
0 upgraded, 4 newly installed, 0 to remove and 21 not upgraded.
Need to get 7039 kB of archives.
After this operation, 26.4 MB of additional disk space will be used.
Do you want to continue? [Y/n] 

Para completar, aquí está el archivo Docker final:

FROM ubuntu:14.04

MAINTAINER Me <[email protected]>

RUN dpkg --add-architecture i386
RUN apt-get update
RUN apt-get install libc6-dbg
RUN apt-get install libc6-dbg:i386

Intente agregar la siguiente línea antes apt-get updateen su Dockerfile:

RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list