[CentOS] getting X started...

I've got a new VM installed for me by a sysadmin who apparently did a minmal install.

As a result I've installed a bunch of things to try to get X going,  including
yum groupinstall "development and creative workstation", "Desktop platform" "mate desktop"
but so far I've not found the incantation to get it to start up X at boot time.

As far as I can tell, it doesn't even try. Once I log in, startx works fine.

Can someone point me to whatever it is I'm missing here?

thanks!
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