Do some setup stuff:
s3cmd --configure
HINTS:
When you are asked for the s3 endpoint, use your hosts (canonical) address YOURHOST instead of s3.amazonaws.com
When asked for DNS-style bucket+hostname:port don’t use the suggested %(bucket)s.YOURHOST. Instead specify your bucket like YOURBUCKETs.YOURHOST. Mind the ‘s’ appended to YOURBUCKET!
Your credentials and settings will be stored in .s3cmd. This file will be read by default so now you can type
s3cmd ls
It should return something like
2020-05-06 s3://YOURBUCKET
bytes and bones 