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:
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