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FS(4)                      Kernel Interfaces Manual                      FS(4)

       fs - file server, dump


       The  file  server  is  the main file system for Plan 9.  It is a stand-
       alone system that runs on a separate computer.  It serves  the  Plan  9
       protocol on a variety of networks including Datakit/URP, Ethernet IL/IP
       and Cyclone fiber direct connections.  The name of the main file server
       at Murray Hill is bootes.

       The file server normally requires all users except to provide authenti-
       cation tickets on each attach(5).   This  can  be  disabled  using  the
       noauth configuration command (see fsconfig(8)).

       The user none is always allowed to attach to bootes without authentica-
       tion but has minimal permissions.

       Bootes maintains three file systems  on  a  combination  of  disks  and
       write-once-read-many (WORM) magneto-optical disks.

       other  is a simple disk-based file system similar to kfs(4).

       main   is  a worm-based file system with a disk-based look-aside cache.
              The disk cache holds modified worm blocks to overcome the write-
              once  property  of  the  worm.   The  cache  also holds recently
              accessed non-modified blocks to speed up  the  effective  access
              time of the worm.  Occasionally (usually daily at 5AM) the modi-
              fied blocks in the disk cache are dumped.  At this time, traffic
              to  the  file system is halted and the modified blocks are rela-
              beled to the unwritten portion of the worm.  After the dump, the
              file  system  traffic  is continued and the relabeled blocks are
              copied to the worm by a background process.

       dump   Each time the main file system is dumped, its root  is  appended
              to  a subdirectory of the dump file system.  Since the dump file
              system is not mirrored with a disk cache, it is read-only.   The
              name  of  the  newly  added root is created from the date of the
              dump: /yyyy/mmdds.  Here yyyy is the full year, mm is the  month
              number,  dd is the day number and s is a sequence number if more
              than one dump is done in a day.  For the first dump, s is  null.
              For the subsequent dumps s is 1, 2, 3, etc.

              The  root  of  the  main file system that is frozen on the first
              dump of March 1, 1992 will be named /1992/0301/ in the dump file

       Place the root of the dump file system on /n/dump and show the modified
       times of the MIPS C compiler over all dumps in February, 1992:

              9fs dump
              ls -l /n/dump/1992/02??/mips/bin/vc

       To get only one line of output for each version of the compiler:

              ls -lp /n/dump/1992/02??/mips/bin/vc | uniq

       Make the other file system available in directory /n/bootesother:

              mount -c /srv/boot /n/bootesother other


       yesterday(1), srv(4), fs(8)
       Sean Quinlan, ``A Cached WORM File System'', Software  -  Practice  and
       Experience, December, 1991