title: Can't install supervisor on a Docker container ubuntu:trusty
body: <p>I am trying to install supervisor inside a Docker ubuntu:trusty container. This is a small example Dockerfile that demonstrates my problem:</p>
  
  <pre><code>FROM ubuntu:trusty
  MAINTAINER someone &lt;someone@somewhere.com&gt;
  
  # Get supervisor:
  RUN apt-get update &amp;&amp; apt-get install -y supervisor
  </code></pre>
  
  <p>When I try to build an image from this Dockerfile, I get this output:</p>
  
  <pre><code>$ docker build -t example .
  Sending build context to Docker daemon 71.17 kB
  Step 0 : FROM ubuntu:trusty
   ---&gt; 91e54dfb1179
  Step 1 : MAINTAINER someone &lt;someone@somewhere.com&gt;
   ---&gt; Running in fc8d787ecfd5
   ---&gt; 0619f1a6c1f1
  Removing intermediate container fc8d787ecfd5
  Step 2 : RUN apt-get update &amp;&amp; apt-get install -y supervisor
   ---&gt; Running in 01285d3a1d4b
  Ign http://archive.ubuntu.com trusty InRelease
  Ign http://archive.ubuntu.com trusty-updates InRelease
  Ign http://archive.ubuntu.com trusty-security InRelease
  Hit http://archive.ubuntu.com trusty Release.gpg
  Get:1 http://archive.ubuntu.com trusty-updates Release.gpg [933 B]
  Get:2 http://archive.ubuntu.com trusty-security Release.gpg [933 B]
  Get:3 http://archive.ubuntu.com trusty Release [11.9 kB]
  Get:4 http://archive.ubuntu.com trusty-updates Release [63.5 kB]
  Ign http://archive.ubuntu.com trusty Release
  Get:5 http://archive.ubuntu.com trusty-security Release [63.5 kB]
  Get:6 http://archive.ubuntu.com trusty/main Sources [1335 kB]
  Get:7 http://archive.ubuntu.com trusty/restricted Sources [5335 B]
  Get:8 http://archive.ubuntu.com trusty/universe Sources [7926 kB]
  Ign http://archive.ubuntu.com trusty/main amd64 Packages/DiffIndex
  Ign http://archive.ubuntu.com trusty/restricted amd64 Packages/DiffIndex
  Get:9 http://archive.ubuntu.com trusty/universe amd64 Packages [7589 kB]
  Get:10 http://archive.ubuntu.com trusty-updates/main Sources [294 kB]
  Get:11 http://archive.ubuntu.com trusty-updates/restricted Sources [4521 B]
  Get:12 http://archive.ubuntu.com trusty-updates/universe Sources [171 kB]
  Get:13 http://archive.ubuntu.com trusty-updates/main amd64 Packages [779 kB]
  Get:14 http://archive.ubuntu.com trusty-updates/restricted amd64 Packages [22.7 kB]
  Get:15 http://archive.ubuntu.com trusty-updates/universe amd64 Packages [407 kB]
  Get:16 http://archive.ubuntu.com trusty-security/main Sources [119 kB]
  Get:17 http://archive.ubuntu.com trusty-security/restricted Sources [1874 B]
  Get:18 http://archive.ubuntu.com trusty-security/universe Sources [34.8 kB]
  Get:19 http://archive.ubuntu.com trusty-security/main amd64 Packages [433 kB]
  Get:20 http://archive.ubuntu.com trusty-security/restricted amd64 Packages [14.8 kB]
  Get:21 http://archive.ubuntu.com trusty-security/universe amd64 Packages [150 kB]
  Get:22 http://archive.ubuntu.com trusty/main amd64 Packages [1743 kB]
  Get:23 http://archive.ubuntu.com trusty/restricted amd64 Packages [16.0 kB]
  Fetched 21.2 MB in 19s (1076 kB/s)
  Reading package lists...
  W: GPG error: http://archive.ubuntu.com trusty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key &lt;ftpmaster@ubuntu.com&gt;
  Reading package lists...
  Building dependency tree...
  Reading state information...
  The following extra packages will be installed:
    libpython-stdlib libpython2.7-minimal libpython2.7-stdlib python
    python-meld3 python-minimal python-pkg-resources python2.7 python2.7-minimal
  Suggested packages:
    python-doc python-tk python-distribute python-distribute-doc python2.7-doc
    binutils binfmt-support
  The following NEW packages will be installed:
    libpython-stdlib libpython2.7-minimal libpython2.7-stdlib python
    python-meld3 python-minimal python-pkg-resources python2.7 python2.7-minimal
    supervisor
  0 upgraded, 10 newly installed, 0 to remove and 12 not upgraded.
  Need to get 4141 kB of archives.
  After this operation, 17.9 MB of additional disk space will be used.
  WARNING: The following packages cannot be authenticated!
    libpython-stdlib python-minimal python python-meld3 supervisor
  E: There are problems and -y was used without --force-yes
  The command '/bin/sh -c apt-get update &amp;&amp; apt-get install -y supervisor' returned a non-zero code: 100
  </code></pre>
  
  <p>There seems to be some authentication problem in there. Sometimes I get other error messages. For example, in a second run this is the output I got:</p>
  
  <pre><code>$ docker build -t example .
  Sending build context to Docker daemon 71.17 kB
  Step 0 : FROM ubuntu:trusty
   ---&gt; 91e54dfb1179
  Step 1 : MAINTAINER someone &lt;someone@somewhere.com&gt;
   ---&gt; Using cache
   ---&gt; 0619f1a6c1f1
  Step 2 : RUN apt-get update &amp;&amp; apt-get install -y supervisor
   ---&gt; Running in 0d4362e9e578
  Ign http://archive.ubuntu.com trusty InRelease
  Ign http://archive.ubuntu.com trusty-updates InRelease
  Ign http://archive.ubuntu.com trusty-security InRelease
  Get:1 http://archive.ubuntu.com trusty Release.gpg [72 B]
  Get:2 http://archive.ubuntu.com trusty-updates Release.gpg [933 B]
  Get:3 http://archive.ubuntu.com trusty-security Release.gpg [933 B]
  Get:4 http://archive.ubuntu.com trusty Release [11.9 kB]
  Get:5 http://archive.ubuntu.com trusty-updates Release [63.5 kB]
  Err http://archive.ubuntu.com trusty Release
  
  Get:6 http://archive.ubuntu.com trusty-security Release [63.5 kB]
  Get:7 http://archive.ubuntu.com trusty-updates/main Sources [294 kB]
  Get:8 http://archive.ubuntu.com trusty-updates/restricted Sources [4521 B]
  Get:9 http://archive.ubuntu.com trusty-updates/universe Sources [171 kB]
  Get:10 http://archive.ubuntu.com trusty-updates/main amd64 Packages [779 kB]
  Get:11 http://archive.ubuntu.com trusty-updates/restricted amd64 Packages [22.7 kB]
  Get:12 http://archive.ubuntu.com trusty-updates/universe amd64 Packages [407 kB]
  Get:13 http://archive.ubuntu.com trusty-security/main Sources [119 kB]
  Get:14 http://archive.ubuntu.com trusty-security/restricted Sources [1874 B]
  Get:15 http://archive.ubuntu.com trusty-security/universe Sources [34.8 kB]
  Get:16 http://archive.ubuntu.com trusty-security/main amd64 Packages [433 kB]
  Get:17 http://archive.ubuntu.com trusty-security/restricted amd64 Packages [14.8 kB]
  Get:18 http://archive.ubuntu.com trusty-security/universe amd64 Packages [150 kB]
  Fetched 2571 kB in 7s (347 kB/s)
  Reading package lists...
  W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://archive.ubuntu.com trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192
  
  W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/Release  
  
  W: Some index files failed to download. They have been ignored, or old ones used instead.
  Reading package lists...
  Building dependency tree...
  Reading state information...
  Package supervisor is not available, but is referred to by another package.
  This may mean that the package is missing, has been obsoleted, or
  is only available from another source
  
  E: Package 'supervisor' has no installation candidate
  The command '/bin/sh -c apt-get update &amp;&amp; apt-get install -y supervisor' returned a non-zero code: 100
  </code></pre>
  
  <p>The output is different probably due to Docker's caching features.</p>
  
  <p>I thought installing stuff on Docker containers should work out of the box with ubuntu:trusty. What am I missing here?</p>