Gnus normally determines whether a group is new or not by comparing
the list of groups from the active file(s) with the lists of
subscribed and dead groups. This isn’t a particularly fast method.
If gnus-check-new-newsgroups is ask-server, Gnus will
ask the server for new groups since the last time. This is both
faster and cheaper. This also means that you can get rid of the list
of killed groups (see Group Levels) altogether, so you may set
gnus-save-killed-list to nil, which will save time both
at startup, at exit, and all over. Saves disk space, too. Why isn’t
this the default, then? Unfortunately, not all servers support this
command.
I bet I know what you’re thinking now: How do I find out whether my
server supports ask-server? No? Good, because I don’t have a
fail-safe answer. I would suggest just setting this variable to
ask-server and see whether any new groups appear within the next
few days. If any do, then it works. If none do, then it doesn’t
work. I could write a function to make Gnus guess whether the server
supports ask-server, but it would just be a guess. So I won’t.
You could telnet to the server and say HELP and see
whether it lists ‘NEWGROUPS’ among the commands it understands. If
it does, then it might work. (But there are servers that lists
‘NEWGROUPS’ without supporting the function properly.)
This variable can also be a list of select methods. If so, Gnus will
issue an ask-server command to each of the select methods, and
subscribe them (or not) using the normal methods. This might be handy
if you are monitoring a few servers for new groups. A side effect is
that startup will take much longer, so you can meditate while waiting.
Use the mantra “dingnusdingnusdingnus” to achieve permanent bliss.