From 3fb06dc104bb66c3ec7be8a95a33845310083999 Mon Sep 17 00:00:00 2001 From: Sebastiaan van Stijn Date: Mon, 19 Jan 2015 00:23:57 +0100 Subject: [PATCH] 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 --- docs/sources/reference/run.md | 6 ++++++ docs/sources/userguide/dockerlinks.md | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/docs/sources/reference/run.md b/docs/sources/reference/run.md index d594066ad0..8bf0d3633f 100644 --- a/docs/sources/reference/run.md +++ b/docs/sources/reference/run.md @@ -647,6 +647,12 @@ mechanism to communicate with a linked container by its alias: If you restart the source container (`servicename` in this case), the recipient container's `/etc/hosts` entry will be automatically updated. +> **Note**: +> Unlike host entries in the `/ets/hosts` file, IP addresses stored in the +> environment variables are not automatically updated if the source container is +> restarted. We recommend using the host entries in `/etc/hosts` to resolve the +> IP address of linked containers. + ## VOLUME (shared filesystems) -v=[]: Create a bind mount with: [host-dir]:[container-dir]:[rw|ro]. diff --git a/docs/sources/userguide/dockerlinks.md b/docs/sources/userguide/dockerlinks.md index e2228cef00..e01604be45 100644 --- a/docs/sources/userguide/dockerlinks.md +++ b/docs/sources/userguide/dockerlinks.md @@ -232,6 +232,12 @@ command to list the specified container's environment variables. > container. Similarly, some daemons (such as `sshd`) > will scrub them when spawning shells for connection. +> **Note**: +> Unlike host entries in the [`/ets/hosts` file](#updating-the-etchosts-file), +> IP addresses stored in the environment variables are not automatically updated +> if the source container is restarted. We recommend using the host entries in +> `/etc/hosts` to resolve the IP address of linked containers. + You can see that Docker has created a series of environment variables with useful information about the source `db` container. Each variable is prefixed with `DB_`, which is populated from the `alias` you specified above. If the `alias`