The way to make docker Collabora work in CentOS 8 / RHEL 8

In centos8, after you installed the Collabora Online following the official documents, it may not works fine when you open a file:

Collabora Online: Cannot connect to the host "https://office.***". Please ask your administrator to check the Collabora Online server setting

This may due to that the DNS in dockor is not work fine. you can check it by:

docker pull library/alpine
docker run --rm -it alpine ping -c4 114.114.114.114
docker run --rm -it alpine ping -c4 www.baidu.com

if can ping IP , and can not ping any Domain, that is the DNS in docker are droped by the firewall in centos8.

Solution:

firewall-cmd --zone=public --remove-interface=docker0 --permanent
firewall-cmd --zone=trusted --add-interface=docker0 --permanent
firewall-cmd --reload

instead of disable firewalld.

I am glad to hear safer solutions.