Some of the back ends, notably nnml,
nnfolder, and nnmaildir, now actually
store the article marks with each group. For these servers,
archiving and restoring a group while preserving marks is fairly
simple.
(Preserving the group level and group parameters as well still requires ritual dancing and sacrifices to the .newsrc.eld deity though.)
To archive an entire nnml, nnfolder,
or nnmaildir server, take a recursive copy of the
server directory. There is no need to shut down Gnus, so
archiving may be invoked by cron or similar. You
restore the data by restoring the directory tree, and adding a
server definition pointing to that directory in Gnus. The
Article
Backlog, Asynchronous
Fetching and other things might interfere with overwriting
data, so you may want to shut down Gnus before you restore the
data.
It is also possible to archive individual nnml,
nnfolder, or nnmaildir groups, while
preserving marks. For nnml or
nnmaildir, you copy all files in the group's
directory. For nnfolder you need to copy both the
base folder file itself (FOO, say), and the marks file
(FOO.mrk in this example).
Restoring the group is done with G m from the Group
buffer. The last step makes Gnus notice the new directory.
nnmaildir notices the new directory automatically,
so G m is unnecessary in that case.