term% ls -F
term% pwd
term% cat index.txt
FS(4)                      Kernel Interfaces Manual                      FS(4)

       fs - file server, dump


       The  file  server was the main file system for Plan 9.  It was a stand-
       alone system that ran on a separate computer.  It  served  the  Plan  9
       protocol  via  the  IL/IP protocols on Ethernets.  The name of the main
       file server at Murray Hill was emelie.

       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 group numbered 9999, normally called noworld,  is  special  on  the
       file  server.   Any  user belonging to that group has attenuated access
       privileges.  Specifically, when checking such a user's access to files,
       the  file's  permission bits are first ANDed with 0770 for normal files
       or 0771 for directories.  The effect is to deny  world  access  permis‐
       sions to noworld users, except when walking directories.

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

       Emelie 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 ac‐
              cessed non-modified blocks to speed up the effective access time
              of  the  worm.  Occasionally (usually daily at 5AM) the modified
              blocks in the disk cache are dumped.  At this time,  traffic  to
              the  file system is halted and the modified blocks are relabeled
              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/emelieother:

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


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

       For the moment, the file server serves both the old (third edition) and
       new (fourth edition) versions of 9P, deciding which to serve by  sniff‐
       ing the first packet on each connection.

       Required IL, thus now deprecated.