This should not be an issue but has been for me on at least 2 servers, one clean install and the other built & then a backup restored, I have several others to check. Posting this info in case any others encounter this idiosyncrasy.
.
The initial error reported when I run yum (even after yum clean all) is:
Loaded plugins: changelog, fastestmirror, post-transaction-actions, priorities, smeserver
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist
http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Name or service not known"
The smeserver-yum rpm has been updated to address this for quite a while but the install/update process for this rpm seems to have failed to run one critical aspect of the update process, namely /etc/e-smith/events/actions/initialize-default-databases, this updates the yum repos to point to the Centos vault (archive).
When I run /etc/e-smith/events/actions/initialize-default-databases manually & then run signal-event yum-modify the yum repos are now updated as expected & yum now works as expected.
In summary, if you have this issue then run the following commands:
To verify you have a yum version that is at least 2.6.0, run:
rpm -q smeserver-yum
If your yum version is older than 2.6.0 then you'll need to download a newer version, the latest yum using wget. To download the latest version run:
cd /root
wget
https://mirrorlist.contribs.org/releases/10.1/smeos/x86_64/Packages/smeserver-yum-2.6.2-1.el7.sme.noarch.rpmthen install this rpm using:
rpm -ivh smeserver-yum-2.6.2-1.el7.sme.noarch.rpm
Once your system has a valid version of smeserver-yum then run:
/etc/e-smith/events/actions/initialize-default-databases
signal-event yum-modify
Yum should now behave as expected.