358 lines
7.3 KiB
Text
358 lines
7.3 KiB
Text
.TH CWFS 4
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.SH NAME
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cwfs, \
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cwfs64, \
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cwfs64x, \
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fs64 - cached-worm file server, dump
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.SH SYNOPSIS
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.B cwfs
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[
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.B -csC
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] [
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.B -n
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.I service
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] [
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.B -a
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.I announce-string
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] ... [
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.B -m
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.I device-map
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] [
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.B -f
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.I config-device
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]
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.SH DESCRIPTION
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.I Cwfs
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is a cached-worm file server that runs
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as a user-mode program and can
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maintain file systems created by
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.IR fs (4),
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the original Plan 9 file server
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that had its own kernel and operated
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a standalone system with disks and
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optical-disc jukebox attached.
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Unlike
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.IR fs (4),
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which could only accept 9P connections over IL/IPv4 on Ethernets
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(or over Datakit and Cyclones, long ago),
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.I cwfs
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accepts 9P connections over any network medium and protocol
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that it can announce on,
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by default TCP (over IPv4 or IPv6).
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Given suitable 9P clients,
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one could even run 9P over
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.IR aan (8)
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or
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.IR tls (3).
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.PP
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The stock
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.I cwfs
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implements a 16K file system block size
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and 32-bit disk addresses,
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in order to be compatible with some existing file systems, notably
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.IR emelie 's.
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These parameters can be changed by recompilation.
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.PP
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.I Cwfs
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places its server 9P connection in
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.BI /srv/ name\f1
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and its command pipe in
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.BI /srv/ name\f1 .cmd,
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where
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.I name
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is the service name.
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.PP
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Options are:
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.TP
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.B -f
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specify
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.IR config-device
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other than the default
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.LR /dev/sdC0/cwfs .
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.TP
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.B -a
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announce on
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.IR announce-string ,
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can be specified multiple times.
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.TP
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.B -C
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use a newer, faster, and incompatible cache-device layout.
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To convert an old file system's cache to the new layout,
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dump the file system, note the last superblock number,
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halt
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.IR cwfs ,
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restart
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.I cwfs
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with
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.BR -cC ,
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.I recover
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the file system, and start
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.I cwfs
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with
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.B -C
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thereafter.
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.TP
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.B -c
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enter the file server's configuration mode
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before starting normal operation.
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.TP
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.B -n
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overrides the
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.I service
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name of the file server's configuration.
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.TP
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.B -s
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Post file descriptor zero in
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.BI /srv/ service
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and read and write protocol messages on file descriptor one.
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.TP
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.B -m
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the file
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.I device-map
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contains a simple device name
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(e.g.,
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.LR w9 )
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and a replacement per line.
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The device name is in the usual
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.I filsys
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notation of
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.IR fsconfig (8).
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The replacement can be the name of an existing file
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(which
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.I cwfs
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will not grow)
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or another such device name.
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For example, the file
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.RS
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.PD
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.IP
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.EX
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w0 /tmp/w0
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h1 w2
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.EE
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.PP
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.PD 0.3v
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would map accesses to device
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.L w0
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to existing file
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.LR /tmp/w0
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and accesses to device
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.L h1
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to device
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.LR w2 ,
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if no file named
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.L w2
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exists.
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.RE
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.PD
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.PP
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The file server normally requires all users except
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.L none
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to provide authentication tickets on each
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.IR attach (5).
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This can be disabled using the
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.B noauth
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configuration command (see
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.IR fsconfig (8)).
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.PP
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The group numbered 9999, normally called
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.BR noworld ,
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is special
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on the file server. Any user belonging to that group has
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attenuated access privileges. Specifically, when checking such
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a user's access to files, the file's permission bits are first ANDed
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with 0770 for normal files or 0771 for directories. The effect is
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to deny world access permissions to
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.B noworld
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users, except
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when walking directories.
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.PP
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The user
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.B none
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is always allowed to attach to
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.B emelie
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without authentication but has minimal permissions.
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.PP
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.B Emelie
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maintains three file systems
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on a combination of disks and
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write-once-read-many (WORM) magneto-optical disks.
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.TP
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.B other
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is a simple disk-based file system not backed by worm.
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.TP
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.B main
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is a worm-based file system with a disk-based
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look-aside cache.
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The disk cache holds
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modified worm blocks
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to overcome the write-once property of the worm.
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The cache also holds recently accessed
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non-modified blocks to
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speed up the effective access time of the worm.
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Occasionally
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(usually daily at 5AM) the modified blocks in the
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disk cache are
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.IR dumped .
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At this time,
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traffic to the file system is halted and the
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modified blocks are relabeled to the unwritten
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portion of the worm.
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After the dump,
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the file system traffic is continued and
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the relabeled blocks are copied to the worm by
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a background process.
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.TP
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.B dump
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Each time the main file system is dumped,
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its root is appended to a subdirectory of the dump file system.
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Since the dump file system is not mirrored with a disk
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cache,
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it is read-only.
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The name of the newly added root is created from the date
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of the dump:
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.BI / yyyy / mmdds\f1.
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Here
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.I yyyy
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is the full year,
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.I mm
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is the month number,
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.I dd
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is the day number and
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.I s
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is a sequence number if more than
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one dump is done in a day.
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For the first dump,
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.I s
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is null.
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For the subsequent dumps
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.I s
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is 1, 2, 3, etc.
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.sp
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The root of the main file system
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that is frozen on the first dump
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of March 1, 1992
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will be named
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.B /1992/0301/
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in the dump file system.
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.SS "Changes from fs"
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.IR fs (4)'s
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IP configuration is ignored and the underlying system's is used.
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.PP
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Various other
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.IR fs (4)
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commands have been omitted since they (or equivalents) can now be
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executed directly on the underlying CPU server,
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notably
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.I date
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and
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.I passwd
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(see
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.IR auth/wrkey ).
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.PP
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Files can be used directly as wren devices by giving
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a file name rooted at
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.I /
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or using double or single quotes. Such a file name
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can be appended to the
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.L w
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device instead of specifying
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.L target
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and
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.L lun
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numbers.
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.PP
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.IR fs (4)'s
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device names
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.L h
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for IDE disks and
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.L m
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for Marvell SATA disks are not supported; use
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.B -m
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to map wren devices to appropriate names under
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.BR /dev/sd* .
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.PP
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The file server kernel seems to have scanned PCI buses
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in reverse order from the other Plan 9 kernels,
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so systems with multiple SCSI cards may find controller
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numbering reversed.
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.B -m
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can be used to compensate for this if you don't want to change
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.I filsys
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declarations.
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.PP
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The file server kernel's
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.I config
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field in NVRAM was overloaded in recent times to hold a
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.IR secstore (1)
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key for the CPU hostowner.
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Since
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.I cwfs
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runs on a CPU kernel,
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the location of its configuration block must be supplied on the command line.
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.PP
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Disk labels are now implemented for
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.B l
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devices.
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At the first access of a side,
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.I cwfs
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will attempt to read the label and verify that it has the correct side
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number and byte order; if either is wrong, it will issue a warning.
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If the label cannot be read,
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.I cwfs
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will attempt to write a new label.
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.PP
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The original file server reserved the rest of the machines RAM for
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io buffers. Where
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.I cwfs
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running under the Plan 9 kernel reserves a settable percentage
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of the remaining user pages. The percentage is read from the
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environment variable
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.B fsmempercent
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which when not set is assumed to be 25% (default).
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.SH EXAMPLES
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Place the root of the
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.B dump
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file system on
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.B /n/dump
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and show the modified times of the MIPS C compiler
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over all dumps in February, 1992:
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.IP
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.EX
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cwfs w0
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9fs dump
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ls -l /n/dump/1992/02??/mips/bin/vc
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.EE
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.PP
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To get only one line of output for each version of the compiler:
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.IP
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.EX
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ls -lp /n/dump/1992/02??/mips/bin/vc | uniq
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.EE
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.SH SOURCE
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.B /sys/src/cmd/cwfs
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.SH SEE ALSO
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.IR yesterday (1),
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.IR fs (3),
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.IR sd (3),
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.IR fs (4),
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.IR srv (4),
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.IR fs (8),
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.IR fsconfig (8)
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.br
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Sean Quinlan,
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``A Cached WORM File System'',
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.I
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Software \- Practice and Experience,
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December, 1991
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.br
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Ken Thompson,
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Geoff Collyer,
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``The 64-bit Standalone Plan 9 File Server''
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.SH BUGS
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For the moment,
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the file server serves both the old (9P1) and new (9P2000) versions of 9P,
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deciding which to serve by sniffing the first packet on each connection.
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.PP
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File system block size and disk address size (32- or 64-bit) are fixed
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at compilation time, and this is not easily changed.
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