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Document that ENV vars are not automatically updated
Unlike the entries in `/etc/hosts`, environment-variables for linked
containers are not automatically updated if the linked container is
restarted.
This adds a note to the documentation in;
https://docs.docker.com/userguide/dockerlinks/#environment-variables
and
https://docs.docker.com/reference/run/#env-environment-variables
To make users aware that this is the case and recommends them to use
the `/etc/hosts` entries in stead.
I added this change because users were expecting environment variables
to be updated automatically as well (https://github.com/docker/docker/issues/10164).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Sebastiaan van Stijn authored on 2015/01/19 08:23:57Showing 2 changed files
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@@ -647,6 +647,12 @@ mechanism to communicate with a linked container by its alias: |
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If you restart the source container (`servicename` in this case), the recipient |
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container's `/etc/hosts` entry will be automatically updated. |
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+> **Note**: |
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+> Unlike host entries in the `/ets/hosts` file, IP addresses stored in the |
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+> environment variables are not automatically updated if the source container is |
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+> restarted. We recommend using the host entries in `/etc/hosts` to resolve the |
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+> IP address of linked containers. |
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+ |
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## VOLUME (shared filesystems) |
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-v=[]: Create a bind mount with: [host-dir]:[container-dir]:[rw|ro]. |
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@@ -232,6 +232,12 @@ command to list the specified container's environment variables. |
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> container. Similarly, some daemons (such as `sshd`) |
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> will scrub them when spawning shells for connection. |
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+> **Note**: |
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+> Unlike host entries in the [`/ets/hosts` file](#updating-the-etchosts-file), |
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+> IP addresses stored in the environment variables are not automatically updated |
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+> if the source container is restarted. We recommend using the host entries in |
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+> `/etc/hosts` to resolve the IP address of linked containers. |
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+ |
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You can see that Docker has created a series of environment variables with |
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useful information about the source `db` container. Each variable is prefixed with |
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`DB_`, which is populated from the `alias` you specified above. If the `alias` |