$ docker run -e "ENV_VAR=foo" ubuntu /bin/bash
Both -e
and --env
can be used to define environment variables inside of a container. It is possible to supply many environment variables using a text file:
$ docker run --env-file ./env.list ubuntu /bin/bash
Example environment variable file:
# This is a comment
TEST_HOST=10.10.0.127
The --env-file
flag takes a filename as an argument and expects each line to be in the VARIABLE=VALUE
format, mimicking the argument passed to --env
. Comment lines need only be prefixed with #
.
Regardless of the order of these three flags, the --env-file
are processed first, and then -e
/--env
flags. This way, any environment variables supplied individually with -e
or --env
will override variables supplied in the --env-var
text file.