gnus: Article Marks

 
 6.4.13.9 Article marks
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 An article identified by ‘uniq’ is considered to have the mark ‘flag’
 when the file ‘.nnmaildir/marks/flag/uniq’ exists.  When Gnus asks
 ‘nnmaildir’ for a group’s marks, ‘nnmaildir’ looks for such files and
 reports the set of marks it finds.  When Gnus asks ‘nnmaildir’ to store
 a new set of marks, ‘nnmaildir’ creates and deletes the corresponding
 files as needed.  (Actually, rather than create a new file for each
 mark, it just creates hard links to ‘.nnmaildir/markfile’, to save
 inodes.)
 
    You can invent new marks by creating a new directory in
 ‘.nnmaildir/marks/’.  You can tar up a maildir and remove it from your
 server, untar it later, and keep your marks.  You can add and remove
 marks yourself by creating and deleting mark files.  If you do this
 while Gnus is running and your ‘nnmaildir’ server is open, it’s best to
 exit all summary buffers for ‘nnmaildir’ groups and type ‘s’ in the
 group buffer first, and to type ‘g’ or ‘M-g’ in the group buffer
 afterwards.  Otherwise, Gnus might not pick up the changes, and might
 undo them.