.NET Core in Linux not reading environment variable

Question

I am trying to get the connectionString from environment variables in Linux, but the problem is that it returns null.

When i type printenv connectionStringin termial it returns the variable, but inside application where i wrote System.Environment.GetEnvironmentVariable("connectionString") it returns null.

Does anyone has any idea why is this happening?

p.s. I am running application in Docker.

Do you execute the 'printenv connectionString' inside the container? — mschuurmans
– mschuurmans, Commented Aug 14, 2018 at 10:43
@mjcs no, how can I execute that inside container, because i'm just executing it in terminal — Ertan Hasani
– Ertan Hasani, Commented Aug 14, 2018 at 10:44
@mjcs yep it returned null, so I added it using export connectionString=... but still when i run the image it takes as null — Ertan Hasani
– Ertan Hasani, Commented Aug 14, 2018 at 11:01

mschuurmans · Accepted Answer · 2018-08-14 11:09:38Z

5

The problem is that environment variables from the host are not available inside the docker container. To pass the environment variable to the container you need to use the following parameter to your run command.

docker run -e NAME=VALUE ...

You can also use a file to set multiple environment variables inside the container (Also useful when you don't want sensitive data in your bash history).

docker run --env-file=env_file_name ...

Take a look at Environment variables in docker

edited Aug 14, 2018 at 11:09

answered Aug 14, 2018 at 10:46

mschuurmans

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3 Comments

Ertan Hasani Over a year ago

I am trying to run docker run -e connectionString connectionStringValue containerName its tells me that docker: invalid reference format: repository name must be lowercase.. While when I run docker run containerName -e connectionString connectionStringValue its throwing Unhandled Exception: System.FormatException: The short switch '-e' is not defined in the switch mappings.

Ertan Hasani Over a year ago

Yep now its working, but is there any other way to get it from environment variables so i dont need to write a lot of -e NAME=VALUE since in my application there are like 10 or more, and I just need to get those from environment

mschuurmans Over a year ago

In my answer i described the option to use a file, this file can contain multiple envorinment variables.

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