I would like to pass the content of a JSON file as an environment variable during the docker run. The docker run is initialed inside a systemd service file.
I did something like:
export TEMP_CONFIG=$(cat /etc/config.json)
and run docker container as follow:
docker run \
--env SERVICE_NAME=${CONTAINER_NAME} \
--env TEMP_CONFIG \
But when I am inside the docker container and try to echo the variable ${TEMP_CONFIG} It's empty.
root@ip-10-109-7-77:/usr/local/nginx/conf# echo ${TEMP_CONFIG}
root@ip-10-109-7-77:/usr/local/nginx/conf#
is there a way to pass content of a JSON file as environment variable?
BTW:
--env TEMP_CONFIG=$(cat /etc/config.json) \
Doing above throws an exception:
docker: Error parsing reference: "\"conf\"" is not a valid repository/tag.
The content of config.json is:
{
"conf" :
{
"appname" :
{
"dbhost" : "xxxx",
"dbname" : "dbname",
"dbuser" : "user",
"dbpassword" : "xxxxx",
"hostname" : "xxxxxx"
},
"cacheBaseDir" : "/storage/",
"iccprofile" : "/etc/nginx/RGB.V1.0.icc",
"tmpDir" : "/tmp",
"mdb" :
{
"user" : "user",
"password" : "xxxxx",
"rights" : "GlobalAdministrator",
"company" : "somecompany"
}
}
}
Any help is definitely appreciated.
You mentioned that you use the docker run command in a systemd unit file. A systemd ExecStart options is not started in a shell. Environment variable substitution is supported by name. Also see the documentation on this:
Basic environment variable substitution is supported. Use "
${FOO}" as part of a word, or as a word of its own, on the command line, in which case it will be replaced by the value of the environment variable including all whitespace it contains, resulting in a single argument.
The doc also says that StartExec is not executed in a shell:
This syntax is intended to be very similar to shell syntax, but only the meta-characters and expansions described in the following paragraphs are understood. Specifically, redirection using "<", "<<", ">", and ">>", pipes using "|", running programs in the background using "&", and other elements of shell syntax are not supported. [...] Note that shell command lines are not directly supported.
However, you can use ExecStart to start a shell and then pass a command using the -c flag (you still need to quote the variable as mentioned in my original answer below):
ExecStart=/bin/bash -c "docker run -e \"TEMP_CONFIG=$(</etc/config.json)\" ..."
Your JSON string contains spaces, and without quoting your shell will interpret everything after the first space as subsequent arguments. So TEMP_CONFIG=$(cat /etc/config.json) is essentially equivalent to:
--env TEMP_CONFIG={ "conf" : { "...
In this case, the TEMP_CONFIG environmant variable will have the value {, and docker run will assume "conf" to be the next argument (in this case, the image name).
Solution: Quote your bash variables:
--env "TEMP_CONFIG=$(cat /etc/config.json)"
Also, don't use cat when you don't have to:
--env "TEMP_CONFIG=$(</etc/config.json)"