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       sn - The sn news system.


       If  you  think  of  a  news spool as a black box, then sn is a bunch of
       programs to put articles in the box (snstore), to view articles  in  it
       (snntpd,  sncat),  remove  old articles (snexpire,sncancel), generate a
       list of  what’s  in  it  (snscan,  snprimedb),  or  display  that  list
       (sndumpdb).   In addition it can go find the articles to put in the box

       The sn system is designed for small sites, spooling a few  dozen  to  a
       few hundred newsgroups.  It is not meant for sites carrying a full news
       feed.  sn is suitable as a replacement for leafnode  (,  by
       Arnt  Gulbrandsen).   It  doesn’t  have leafnode’s intelligence when it
       comes to retrieving upstream articles, but is  less  demanding  on  the
       filesystem and takes up less disk space.

       sn supports local news groups.

       sn  tries  to  create  aliases  for  crossposts  instead of storing the
       article multiple times.

       sn  can  compress  articles  to  save  disk  space.   Compressing   and
       uncompressing take place transparently.

       sn  doesn’t  use  configuration  files.  Instead, you write small shell
       scripts to customize sn’s behaviour.


       sn has been tested only against Linux ver. 2.0.  It makes heavy use  of
       mmap(2)  in  MAP_SHARED  and  MAP_WRITE  mode,  so  it  won’t  work  on
       pre-1.3.45  or  so.   I  (  am  interested  in  bug
       reports, comments, and suggestions.


       The news spool is /var/spool/sn, which all sn programs need in order to
       run.  It contains  the  group  directories  in  format
       rather  than  the  traditional  news/group/name.   Each  such directory
       contains article files, named serially from 1, 2,  etc.   Each  article
       file  consists  of up to 10 articles, which reduces the number of files
       and inodes required.  These article files are mmap(2)ed before use, and
       they are cached to reduce search time.  sn tries to keep the headers of
       these articles bunched together, to reduce the memory footprint.

       In addition  to  the  article  files,  each  newsgroup  directory  also
       contains  files  which  control  the  behaviour  of the sn system.  All
       control files have filenames beginning with a dot, and they all  reside
       in  the  group  directory  in  which  they  are  to  have  effect.   In
       particular, if  the  group  directory  does  not  have  a  subdirectory
       .outgoing in it, it is considered a local news group.


       When  retrieving  articles,  there  is a window of time between when an
       article is first marked as wanted and when it is committed to the  news
       spool.   Within  this  window  it  is possible to have the same article
       committed by a separate process.  This defeats the aliasing feature  so
       you could end up with more than one copy of an identical article.

       The   ID   database  will  only  store  one  instance  of  an  articles
       {ID,group,serial} tuple.  After the second copy  is  committed  to  the
       spool, snstore will try to commit it in the ID database, and will fail.
       So it is possible that after the article has been expired, another copy
       will still remain, but be inaccessible if requested by its ID.

       sn  doesn’t  sync  the  ID  database  after each write, so it could get
       corrupted.   If  you  suspect  it  is  corrupted,  delete   the   files
       /var/spool/sn/.table,             /var/spool/sn/.chain,             and
       /var/spool/sn/.newsgroup, making sure snntpd and snget  aren’t  running
       or scheduled to do so.  Then run
       cd /var/spool/sn; snscan -n * |snprimedb
       This will recreate the ID database.


       sncat  prints  out  the specified articles.  This is useful if you want
              to transport the spool to another system.

              dumps the ID database.  It is not normally used.

              expires articles in the spool.

              is the back end of the article fetcher.  You  can  use  suck  (a
              separate package) instead.

       snget  is the front end of the article fetcher.

       snmail converts  a normal email message into a news article.  It can be
              used to turn a mailing list into a local newsgroup.

              is a script to create newsgroup directories.

              is a script to delete newsgroup directories  and  flush  the  ID
              database of references to those articles.

       snntpd is the news server (an nnrpd).

              feeds  the  ID  database  from  formatted  standard input.  This
              database is what permits articles to be specified by  their  ID.
              This program is not used in normal operation.

       snscan scans  the  specified  articles and outputs a line consisting of
              the article’s  ID,  newsgroup,  and  serial  number  within  the
              newsgroup.   This  output  is suitable for feeding to snprimedb.
              This program is not used in normal operation.

       snsend takes articles on standard input and distributes them  according
              to the type of newsgroup.

              Like  snsend,  but  considers all newsgroups as local, so stores
              all articles locally only.

              cancels articles, so they are no longer available locally.


       Exit codes
              All sn programs exit 0 on success, 1 on invocation error;  2  on
              system  error;  3 on format or protocol error.  Other exit codes
              are possible.

              sn  programs  take  -d  to  enable  verbose  messages  (may   be
              repeated),  and -V, which displays the version and exits.  Where
              a  network  timeout  is  appropriate,  this  is  specified  with
              -t timeout, in seconds.  -P indicates the pid should be included
              in any status output.  Other options are possible.

              sn programs will take the contents  of  the  SNROOT  environment
              variable  as  the  news  spool  rather than /var/spool/sn.  If a
              program will need to run another, it appends  /usr/sbin  to  its
              PATH variable if /usr/sbin is not already present.


       sncat(8),  sndumpdb(8),  snexpire(8),  snfetch(8), snget(8), snmail(8),
       snnewgroup(8),  sndelgroup(8),  snntpd(8),   snprimedb(8),   snscan(8),
       snstore(8), snsend(8)