Por que instalar um libc6 para um arco diferente não funciona para o armhf?

Question

Estou tentando fazer a compilação cruzada funcionar em um sistema de 64 bits que já possui o i386 ativado:

$ dpkg --print-architecture
amd64
$ dpkg --print-foreign-architectures
i386
armhf

Apenas os repositórios jessie estão ativados:

$ apt-cache policy libc6:armhf
libc6:armhf:
  Installed: (none)
  Candidate: 2.19-18+deb8u1
  Version table:
     2.19-18+deb8u1 0
        700 http://http.debian.net/debian/ jessie/main armhf Packages

No entanto, estou recebendo um conflito estranho que não consigo decifrar (" libc6:armhf : Breaks: libc6 (!= 2.19-18+deb8u1) "), a saída completa do apt-get é encontrada abaixo.

O i386 libc está vivendo pacificamente neste sistema, mas a versão armhf (e armel for this matter) falha. O que eu faço com esse erro do apt-get e como posso corrigi-lo?

$ apt-get install libc6: armhf     Lendo listas de pacotes ... Concluído     Construindo árvore de dependências
    Lendo informações de estado ... Concluído     Alguns pacotes não puderam ser instalados. Isso pode significar que você tem     solicitou uma situação impossível ou se você estiver usando a instável     distribuição que alguns pacotes necessários ainda não foram criados     ou foi movido para fora da Entrada.     As informações a seguir podem ajudar a resolver a situação:

The following packages have unmet dependencies:
 init : PreDepends: systemd-sysv but it is not going to be installed or
                    sysvinit-core but it is not going to be installed or
                    upstart
 libc6 : Breaks: libc6:armhf (!= 2.19-19) but 2.19-18+deb8u1 is to be installed
 libc6:armhf : Breaks: libc6 (!= 2.19-18+deb8u1) but 2.19-19 is to be installed
 libcurl3-gnutls : Depends: libgnutls-deb0-28 (>= 3.3.0) but it is not going to be installed
                   Depends: libldap-2.4-2 (>= 2.4.7) but it is not going to be installed
                   Depends: librtmp1 (>= 2.4+20131018.git79459a2-3~) but it is not going to be installed
                   Depends: libssh2-1 (>= 1.2.6) but it is not going to be installed
                   Recommends: ca-certificates but it is not going to be installed
 libqt5core5a : Depends: libglib2.0-0 (>= 2.22.0) but it is not going to be installed
                Depends: libicu52 (>= 52~m1-1~) but it is not going to be installed
 libqt5gui5 : Depends: fontconfig
              Depends: libegl1-mesa (>= 7.8.1) but it is not going to be installed or
                       libegl1-x11
              Depends: libfontconfig1 (>= 2.11) but it is not going to be installed
              Depends: libgbm1 (>= 8.1~0) but it is not going to be installed
              Depends: libgl1-mesa-glx but it is not going to be installed or
                       libgl1
              Depends: libglib2.0-0 (>= 2.12.0) but it is not going to be installed
              Depends: libgtk2.0-0 (>= 2.24.0) but it is not going to be installed
              Depends: libharfbuzz0b (>= 0.9.11) but it is not going to be installed
              Depends: libice6 (>= 1:1.0.0) but it is not going to be installed
              Depends: libpango-1.0-0 (>= 1.14.0) but it is not going to be installed
              Depends: libsm6 but it is not going to be installed
              Depends: libx11-6 but it is not going to be installed
              Depends: libx11-xcb1 but it is not going to be installed
              Depends: libxcb-glx0 but it is not going to be installed
              Depends: libxcb-icccm4 (>= 0.4.1) but it is not going to be installed
              Depends: libxcb-image0 (>= 0.2.1) but it is not going to be installed
              Depends: libxcb-keysyms1 (>= 0.4.0) but it is not going to be installed
              Depends: libxcb-randr0 (>= 1.3) but it is not going to be installed
              Depends: libxcb-render-util0 but it is not going to be installed
              Depends: libxcb-render0 but it is not going to be installed
              Depends: libxcb-shape0 but it is not going to be installed
              Depends: libxcb-shm0 but it is not going to be installed
              Depends: libxcb-sync1 but it is not going to be installed
              Depends: libxcb-xfixes0 but it is not going to be installed
              Depends: libxcb-xkb1 but it is not going to be installed
              Depends: libxcb1 but it is not going to be installed
              Depends: libxi6 (>= 2:1.2.99.4) but it is not going to be installed
              Depends: libxkbcommon-x11-0 (>= 0.4.0) but it is not going to be installed
              Depends: libxrender1 but it is not going to be installed
 libqt5widgets5 : Depends: libglib2.0-0 (>= 2.12.0) but it is not going to be installed
                  Depends: libx11-6 but it is not going to be installed
 libssl1.0.0 : Depends: debconf (>= 0.5) but it is not going to be installed or
                        debconf-2.0
 live-config-sysvinit : Depends: sysvinit-core but it is not going to be installed or
                                 sysvinit (< 2.88dsf-44) but it is not going to be installed
 nginx-common : Depends: init-system-helpers (>= 1.18~) but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

    

Answer 1

libc6 : Breaks: libc6:armhf (!= 2.19-19) but 2.19-18+deb8u1 is to be installed
libc6:armhf : Breaks: libc6 (!= 2.19-18+deb8u1) but 2.19-19 is to be installed

Uma das regras do Debian multiarch é que as versões devem corresponder exatamente entre as arquiteturas. Debian jessie tem a versão 2.19-18+deb8u1 mas de alguma forma você acabou com 2.19-19 instalado para amd64 (e presumivelmente i386).

Como seu sistema entrou nesse estado em primeiro lugar eu não sei. Talvez em algum momento você ou um administrador anterior tenha alterado o sources.list para o teste e depois o tenha alterado para o jessie.

Baixar 2.19-19 para armhf de snapshot.debian.org e instalá-lo manualmente com o dpkg pode ser uma solução.

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