Docker connectivity issue: apt/apk do not work inside docker container and during docker build

问题

I am struggling since two days with the following problem. Packages management systems fail when I try to run them in order to build a new container image, I tried with alpine:latest and ubuntu:latest. I get the same behavior if I try to use them from a running container, even if I use the --network host option.

For example if I try to build the following container:

FROM alpine:latest
RUN apk update

like this:

docker build --no-cache -t test .

I get:

ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.9/main: could not connect to server (check repositories file)
WARNING: Ignoring APKINDEX.b89edf6e.tar.gz: No such file or directory
ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.9/community: could not connect to server (check repositories file)
WARNING: Ignoring APKINDEX.737f7e01.tar.gz: No such file or directory

and with ubuntu:

FROM ubuntu:latest
RUN apt-get update

I get:

Sending build context to Docker daemon  3.954MB
Step 1/2 : FROM ubuntu:latest
---> 47b19964fb50
Step 2/2 : RUN apt-get update
---> Running in 4c637396e7be
Err:1 http://archive.ubuntu.com/ubuntu bionic InRelease
Could not connect to 127.0.0.1:3000 (127.0.0.1). - connect (111:Connection refused)
Err:2 http://security.ubuntu.com/ubuntu bionic-security InRelease
Could not connect to 127.0.0.1:3000 (127.0.0.1). - connect (111:Connection refused)
Err:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
Unable to connect to 127.0.0.1:3000:
Err:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease
Unable to connect to 127.0.0.1:3000:
Reading package lists...
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Could not connect to 127.0.0.1:3000 (127.0.0.1). - connect (111: Connection refused)
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Unable to connect to 127.0.0.1:3000:
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Unable to connect to 127.0.0.1:3000:
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Could not connect to 127.0.0.1:3000 (127.0.0.1). connect (111: Connection refused)
W: Some index files failed to download. They have been ignored, or old ones used instead.
Removing intermediate container 4c637396e7be
---> e41da39b1a0d
Successfully built e41da39b1a0d
Successfully tagged test:latest

I am working with Docker version 18.09.3, build 774a1f4, on a ubuntu 16.04 host. My system runs behind a router. I already tried the strategies suggested in this answer and also the one in this answer without any luck. Even stranger if I ping from the adiazmor/docker-ubuntu-with-ping as follow:

  docker run --rm -it adiazmor/docker-ubuntu-with-ping
root@a774331799d3:/# ping google.com
PING google.com (216.58.205.46): 56 data bytes
64 bytes from 216.58.205.46: icmp_seq=0 ttl=53 time=44.976 ms
64 bytes from 216.58.205.46: icmp_seq=1 ttl=53 time=43.661 ms
64 bytes from 216.58.205.46: icmp_seq=2 ttl=53 time=43.471 ms
64 bytes from 216.58.205.46: icmp_seq=3 ttl=53 time=44.066 ms
64 bytes from 216.58.205.46: icmp_seq=4 ttl=53 time=43.849 ms

It works but then apt-get update fails as before. I am running out of ideas. Any help is appreciated.

Update: It seems that some containers are able to find the proper DNS server while others are not.

Indeed if I run:

docker run --rm -i busybox nslookup google.com

It doesn't work:

Unable to find image 'busybox:latest' locallylatest: Pulling from library/busybox
697743189b6d: Pull complete 
Digest: sha256:061ca9704a714ee3e8b80523ec720c64f6209ad3f97c0ff7cb9ec7d19f15149f
Status: Downloaded newer image for busybox:latest
Server:         8.8.8.8
Address:        8.8.8.8:53

Non-authoritative answer:
Name:   google.com
Address: 2a00:1450:4002:807::200e

*** Can't find google.com: No answer

but If I run:

docker run --rm -it tutum/dnsutils nslookup google.com

it works:

Unable to find image 'tutum/dnsutils:latest' locally
latest: Pulling from tutum/dnsutils
a3ed95caeb02: Pull complete 
0d4f8675aa34: Pull complete 
7cf67d95acf6: Pull complete 
56692d2aae61: Pull complete 
349ad02ed73a: Pull complete 
Digest: sha256:d2244ad47219529f1003bd1513f5c99e71655353a3a63624ea9cb19f8393d5fe
Status: Downloaded newer image for tutum/dnsutils:latest
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
Name:   google.com
Address: 216.58.205.78

回答1:

Update: the root cause of problem was in my local user configuration (/home/myuser/.docker/config.json), indeed it was setting the default proxy to 127.0.0.1:3000.

Ok I found the problem at least for ubuntu, it has been all the time in front of me. Believe it or not the official ubuntu image comes with both http_proxy and HTTP_PROXY set to 127.0.0.1:3000. Indeed I just tested this change to my Dockerfile.ubuntu:

FROM ubuntu:latest
RUN echo $HTTP_PROXY && echo $http_proxy && unset HTTP_PROXY && unset http_proxy && apt-get update

and it works fine:

$ docker build --no-cache -f Dockerfile.ubuntu .
Sending build context to Docker daemon  3.956MB
Step 1/2 : FROM ubuntu:latest
 ---> 47b19964fb50
Step 2/2 : RUN echo $HTTP_PROXY && echo $http_proxy && unset HTTP_PROXY && unset http_proxy && apt-get update
 ---> Running in bc697aa04846
http://127.0.0.1:3000
http://127.0.0.1:3000
Get:1 http://archive.ubuntu.com/ubuntu bionic InRelease [242 kB]
Get:2 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Get:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages [358 kB]
Get:5 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:6 http://security.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages [3910 B]
Get:7 http://security.ubuntu.com/ubuntu bionic-security/restricted amd64 Packages [5436 B]
Get:8 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [157 kB]
Get:9 http://archive.ubuntu.com/ubuntu bionic/restricted amd64 Packages [13.5 kB]
Get:10 http://archive.ubuntu.com/ubuntu bionic/multiverse amd64 Packages [186 kB]
Get:11 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages [11.3 MB]
Get:12 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages [1344 kB]
Get:13 http://archive.ubuntu.com/ubuntu bionic-updates/restricted amd64 Packages [10.8 kB]
Get:14 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [946 kB]
Get:15 http://archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 Packages [6966 B]
Get:16 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [708 kB]
Get:17 http://archive.ubuntu.com/ubuntu bionic-backports/universe amd64 Packages [3650 B]
Fetched 15.6 MB in 10s (1578 kB/s)
Reading package lists...
Removing intermediate container bc697aa04846
 ---> 0b6a1f333528
Successfully built 0b6a1f333528

Still this appears to me as a violation of the isolation principle but maybe there is a good reason and I would like to know it, can anyone clarify why these two env variables are set by default?

Update:

The problem was the same also in alpine.

来源：https://stackoverflow.com/questions/55079577/docker-connectivity-issue-apt-apk-do-not-work-inside-docker-container-and-durin

标签

Docker

apk

apt