Stef asked:
I am needing to connect to the internet from inside a container.
Initially the Docker daemon was not able to connect to the internet and I was unable to even run:
docker pull hello-world
I resolved this by specifying a manual proxy in the docker desktop GUI settings, under resources
Once I manually set the proxy I was able to pull the hello-world image – so I know this proxy works.
I then created a test Dockerfile to see if I could get a container to connect to the internet when building an image, and this is the Dockerfile:
FROM mcr.microsoft.com/windows/servercore:1903
RUN curl 'www.google.co.za'
and got this output:
PS C:\Projects\Test> docker build -t test:01 .
Sending build context to Docker daemon 3.906GB
Step 1/2 : FROM mcr.microsoft.com/windows/servercore:1903
---> 66c07b0d3e85
Step 2/2 : RUN curl 'www.google.co.za'
---> Running in 99f79ea70731
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0curl: (6) Could not resolve host: 'www.google.co.za'
The command 'cmd /S /C curl 'www.google.co.za'' returned a non-zero code: 6
As was suggested here I tried adding a DNS as follows:
"dns": ["1.1.1.1"]
but got the same result as above.
I had previously had issues in Linux containers where I couldn’t install packages inside the container and I had to add the following to the Dockerfile which worked:
ENV HTTP_PROXY http://myproxy:3128
ENV http_proxy http://myproxy:3128
I have tried doing this in my test Dockerfile and I get this result (note that this is the output without the dns settings):
PS C:\Projects\Test> docker build -t test:01 .
Sending build context to Docker daemon 3.906GB
Step 1/4 : FROM mcr.microsoft.com/windows/servercore:1903
---> 66c07b0d3e85
Step 2/4 : ENV HTTP_PROXY http://myproxy.com:3128
---> Using cache
---> d6bbca2c1984
Step 3/4 : ENV http_proxy http://myproxy.com:3128
---> Using cache
---> a22311c57c8d
Step 4/4 : RUN curl 'www.google.co.za'
---> Running in 3e3be3786b62
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 874 100 874 0 0 874 0 0:00:01 --:--:-- 0:00:01 1189
<HTML><HEAD>
<TITLE>Network Error</TITLE>
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<big>Network Error (dns_unresolved_hostname)</big>
<BR>
<BR>
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</TD></TR>
<TR><TD>
<FONT face="Helvetica">
Your requested host "'www.google.co.za'" could not be resolved by DNS.
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<FONT face="Helvetica">
</FONT>
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<BR>
For assistance, contact your network support team.<br><br>Your request was categorized by Blue Coat Web Filter as 'none'. <br>If you wish to question or dispute this result, please click <a href="http://sitereview.bluecoat.com/sitereview.jsp?referrer=136&url=http://'www.google.co.za'/">here</a>.
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</TD></TR>
</TABLE>
</blockquote>
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</BODY></HTML>
Removing intermediate container 3e3be3786b62
---> 79dcdbf32644
Successfully built 79dcdbf32644
Successfully tagged test:01
If I add the dns settings back into the docker GUI I get this output:
PS C:\Projects\Test> docker build -t test:01 .
Sending build context to Docker daemon 3.906GB
Step 1/4 : FROM mcr.microsoft.com/windows/servercore:1903
---> 66c07b0d3e85
Step 2/4 : ENV HTTP_PROXY http://myproxy.com:3128
---> Running in 4ac3e6e23b5f
Removing intermediate container 4ac3e6e23b5f
---> 6bfbb6923789
Step 3/4 : ENV http_proxy http://myproxy.com:3128
---> Running in 7e7b08cef7b3
Removing intermediate container 7e7b08cef7b3
---> 4a827371e6fa
Step 4/4 : RUN curl 'www.google.co.za'
---> Running in 317a2ea37342
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:00:10 --:--:-- 0curl: (5) Could not resolve proxy: myproxy.com
The command 'cmd /S /C curl 'www.google.co.za'' returned a non-zero code: 5
So with the dns settings it can’t resolve the proxy and without the dns settings it can’t resolve the URL. I don’t know how to proceed from here.
My answer:
You should remove the literal single quotes from your curl command. They are being sent to the proxy server, so that it tries to find a host named 'www.google.co.za' instead of the desirable www.google.co.za.
It should instead be:
RUN curl www.google.co.za
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