Merge pull request #103 from vsoch/docs/2.4

undoing my mistakes

Author: GodloveD

pages/docs/user-docs/docs-bootstrap-image.md

@@ -152,6 +152,15 @@ You can add environment variables to be sourced when the container is used in th
     export VADER LUKE SOLO
 ```
 
+You can also add environment variables to your container in the `%post` section (see below) using the following syntax:
+
+```
+%post
+    echo 'export JAWA_SEZ=wutini' >>$SINGULARITY_ENVIRONMENT
+```
+
+Variables added to your container using the `$SINGULARITY_ENVIRONMENT` syntax take precedence over those added in the `%environment` section. 
+
 See <a href="/docs-environment-metadata">Environment and Metadata</a> for more information about the `%labels` and `%environment` sections.
 
 

pages/docs/user-docs/docs-bootstrap.md

@@ -101,6 +101,17 @@ Beginning with Singularity v2.3 you can set up your environment using the `%envi
     export PATH=/opt/good/stuff:$PATH
 ```
 
+In older versions of Singularity you could set up your container's environment by adding text to a file called `/environment`.  This method is now deprecated.  If you need to add environment variables to your container during the `%post` section (perhaps because you will not know the values of some variables until some installation steps have completed).  You can do so with the following syntax:
+
+```
+%post
+    echo 'export PATH=/opt/good/stuff:$PATH' >>$SINGULARITY_ENVIRONMENT
+```
+
+Text in the `%environment` section will be appended to a file called `/.singularity.d/env/90-environment.sh`.  Text redirected to the `$SINGULARITY_ENVIRONMENT` variable will added to a file called `/.singularity.d/env/91-environment.sh`.  At runtime, scripts in `/.singularity/env` are sourced in order.
+
+This means that variables in `$SINGULARITY_ENVIRONMENT` take precedence over those added via `%environment
+
 ### %runscript
 The `%runscript` is another scriptlet, but it does not get executed during bootstrapping. Instead it gets persisted within the container to a file called `/singularity` which is the execution driver when the container image is ***run*** (either via the `singularity run` command or via executing the container directly).
 

pages/docs/user-docs/docs-environment-metadata.md

@@ -23,6 +23,15 @@ From: ubuntu:latest
     export VARIABLE_NAME
 ```
 
+If you need to add an environment variable to your container during the `%post` section, you can do so using the `$SINGULARITY_ENVIRONMENT` variable with the following syntax:
+
+```
+%post
+    echo 'export VARIABLE_NAME=VARIABLE_VALUE' >>$SINGULARITY_ENVIRONMENT
+```
+
+Text in the `%environment` section will be appended to the file `/.singularity.d/env/90-environment.sh` while text redirected to `$SINGULARITY_ENVIRONMENT` will end up in the file `/.singularity.d/env/91-environment.sh`.  Because files in `/.singularity.d/env` are sourced in alpha-numerical order, this means that variables added using `$SINGULARITY_ENVIRONMENT` take precedence over those added via the `%environment` section.
+
 Forget something, or need a variable defined at runtime? You can set any variable you want inside the container by prefixing it with "SINGULARITYENV_". It will be transposed automatically and the prefix will be stripped. For example, let's say we want to set the variable `HELLO` to have value `WORLD`. We can do that as follows:
 
 ```bash
@@ -78,7 +87,7 @@ singularity inspect dino.img
 }
 ```
 
-You will notice that the one label doesn't belong to the label schema, `MAINTAINER`. This was a user provided label during bootstrap. For versions earlier than 2.4, containers did not use the label schema:
+You will notice that the one label doesn't belong to the label schema, `MAINTAINER`. This was a user provided label during bootstrap. Finally, for Singularity greater than version 2.4, the image build size is added as a label, `org.label-schema.build-size`, and the label schema is used, period. For versions earlier than 2.4, containers did not use the label schema, and looked like this:
 
 
 ```bash