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 authentication tickets on
each attach(5). This can be disabled using the noauth configuration command (see fscon-
The user none is always allowed to attach to bootes without authentication but has minimal
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 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 system.
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:
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,