The repository 'http://ftp.debian.org/debian buster-backports Release' does not have a Release file.

[jmalyik]

Without the commented out line below the docker build failed when one would like to install any additional os package to the container:

Steps to reproduce: create a Dockerfile with something similar content:

FROM  osixia/openldap:1.5.0

ENV LDAP_LOG_LEVEL "0"
ENV LDAP_ORGANISATION "LOCAL"
ENV LDAP_DOMAIN "test.local"
ENV LDAP_ADMIN_PASSWORD "password"
ENV LDAP_BASE_DN  "dc=test,dc=local"
ENV LDAP_TLS_ENFORCE false

#RUN sed -i "s|deb http://ftp.debian.org/debian buster-backports main||g" /etc/apt/sources.list
RUN apt update && apt install -y vim

Maybe there is a better option than removing the buster-backports repo, this was what worked for me for now.