Moving (?) from Zentyal to nethserver

Filippo: I don’t want to hijack this thread, but when I do yum update I get the following error:

Loaded plugins: changelog, fastestmirror, nethserver_events, presto
Setting up Update Process
Determining fastest mirrors
YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/
removing mirrorlist with no valid mirrors: /var/cache/yum/x86_64/6/centos-base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: centos-base

For some reason the mirrorlist.txt files are missing from centos-base and centos-updates, but they are both there for nethserver-base and nethserver-updates. Any thoughts on what might have deleted those files?