FS(4)							     Kernel Interfaces Manual							     FS(4)

NAME

       fs - file server, dump

SYNOPSIS

       none

DESCRIPTION

       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 authentication 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 authentication 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 modified blocks in the disk cache are dumped.  At this time, traffic to the file sys-
	      tem  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  sys-
	      tem  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 sys-
	      tem.

EXAMPLES

       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

SOURCE

       /sys/src/fs

SEE ALSO

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

																	     FS(4)