server old-ip-or-hostname-here prefer [burst iburst]

##</code><code>##

server new-ip-here prefer burst iburst  

 
server another-ip-or-hostname-here [burst iburst]   

##</code><code>##

 
nothing (remove the line)

##</code><code>##

server 127.127.1.0

##</code><code>##

perl -p -i -e 's/server [\w\.]+ prefer.*/server new-ip-here prefer burst iburst/g' ntp.conf