In case it helps...
I am giving a try to this docker componse example, and for some strange reason, docker was stuck in this block of code in the Dockerfile for one of the components:
# grab gosu for easy step-down from root ENV GOSU_VERSION 1.7 RUN set -x \ && apt-get update && apt-get install -y --no-install-recommends ca-certificates wget && rm -rf /var/lib/apt/lists/* \ && wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture)" \ && wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture).asc" \ && export GNUPGHOME="$(mktemp -d)" \ && gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 \ && gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu \ && rm -r "$GNUPGHOME" /usr/local/bin/gosu.asc \ && chmod +x /usr/local/bin/gosu \ && gosu nobody true
Specifically, in this line:
gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4
It is a really simple command... I could ping the keyserver, I checked the website and everything looked ok, but it wasn't working, neither in the host machine or inside a container... The response was the same: timeout while getting the keys
So... Here comes netstat to the rescue:
# netstat -natop | grep gpg tcp 0 1 192.168.1.10:34340 184.108.40.206:11371 SYN_SENT 8653/gpg2keys_hkp on (7,10/3/0)
SYN_SENT? So it was trying to stablish the connection, but there wasn't any response from the remote host... In that port
It turns out I recently upgraded my internet connection, and the new router allows you to customize the firewall security levels (you know, low, medium, high and paranoid... yeah, I am using the latter). I noticed that port 11371 was not defined in as a "known service", so I wasn't able to reach it from within my home network.
As soon as I allowed the connection to that port:
# gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 gpg: solicitando clave BF357DD4 de hkp servidor ha.pool.sks-keyservers.net gpg: /root/.gnupg/trustdb.gpg: se ha creado base de datos de confianza gpg: clave BF357DD4: clave pública "Tianon Gravi <firstname.lastname@example.org>" importada gpg: no se encuentran claves absolutamente fiables gpg: Cantidad total procesada: 1 gpg: importadas: 1 (RSA: 1)
So make sure all your ip flows are open, even for such a small thing as this one...
Take care out there!