"If they did edit it and have a working system and then install the update,
what will happen? If I'm reading you right, their changes, that made the
system work, will be lost. Is that right?"
If they were to upgrade to a cobbler based MAAS version, then yes their changes (in /etc/dnsmasq.conf) will be lost because cobbler will overwrite this file as explained above.
If they upgrade to the proposed SRU (which is cobblerless MAAS), their changes in /etc/dnsmasq.conf won't be lost because the SRU'd version of MAAS does not use dnsmasq, since it runs its own instance of isc-dhcp, and ships its own config file, leases file, etc.
Scott,
"If they did edit it and have a working system and then install the update,
what will happen? If I'm reading you right, their changes, that made the
system work, will be lost. Is that right?"
If they were to upgrade to a cobbler based MAAS version, then yes their changes (in /etc/dnsmasq.conf) will be lost because cobbler will overwrite this file as explained above.
If they upgrade to the proposed SRU (which is cobblerless MAAS), their changes in /etc/dnsmasq.conf won't be lost because the SRU'd version of MAAS does not use dnsmasq, since it runs its own instance of isc-dhcp, and ships its own config file, leases file, etc.
Hope this answer your questions.