Doc: Document list of supported environmental varaibles. (#2864)

fixes #2773

docs/minio-env-variables.md

@@ -0,0 +1,47 @@
+# Minio Environmental varaibles
+
+#### MINIO_ENABLE_FSMETA
+When enabled, minio-FS saves the HTTP headers that start with `X-Amz-Meta-` and `X-Minio-Meta`. These header meta data can be retrieved on HEAD and GET requests on the object.
+
+#### MINIO_PROFILER
+Used for Go profiling. Supported values are:
+
+`cpu` - for CPU profiling
+
+`mem` - for memory profiling
+
+`block` - for block profiling
+
+#### MINIO_PROFILE_DIR
+
+Path where cpu/mem/block profiling files are dumped
+
+#### MINIO_BROWSER
+
+setting this to `off` disables the minio browser.
+
+#### MINIO_ACCESS_KEY
+
+Minio access key.
+
+#### MINIO_SECRET_KEY
+
+Minio secret key.
+
+#### MINIO_CACHE_SIZE
+
+Set total cache size in NN[GB|MB|KB]. Defaults to 8GB
+
+Ex: MINIO_CACHE_SIZE=2GB
+
+#### MINIO_CACHE_EXPIRY
+
+Set the object cache expiration duration in NN[h|m|s]. Defaults to 72 hours.
+
+Ex. MINIO_CACHE_EXPIRY=24h
+
+#### MINIO_MAXCONN
+
+Limit of the number of concurrent http requests.
+
+Ex. MINIO_MAXCONN=500