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.TH CFS 4
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.SH NAME
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cfs \- cache file system
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.SH SYNOPSIS
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.B cfs
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.B -s
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.RB [ -dknrS ]
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.RB [ -f
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.IR partition ]
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.PP
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.B cfs
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.B -a
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.I netaddr
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.RB [ -dknrS ]
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.RB [ -f
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.IR partition ]
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.RI [ mtpt ]
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.PP
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.B cfs
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.B -F
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.I srvfile
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.RB [ -dknrS ]
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.RB [ -f
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.IR partition ]
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.RI [ mtpt ]
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.SH DESCRIPTION
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.I Cfs
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is a user-level file server that caches data from remote
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files onto a local disk.
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It is normally started by the kernel at boot time, though users may start
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it manually.
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.I Cfs
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is interposed between the kernel and a network connection to a
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remote file server to improve the
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efficiency of access across slow network connections such as modem
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lines.
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On each open of a file
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.I cfs
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checks the consistency of cached information and discards any old
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information for that file.
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.PP
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.I Cfs
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mounts onto
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.I mtpt
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(default
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.BR / )
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after connecting to the file server.
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.PP
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The options are:
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.TF -
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.PD
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.TP
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.BI "a " netaddr
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dial the destination
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.I netaddr
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to connect to a remote file server.
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Exclusive with
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.BR -F .
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.TP
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.B d
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turn on debugging.
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.TP
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.BI "f " partition
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use file
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.I partition
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as the cache disk partition.
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.TP
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.BI "F " srvfile
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open
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.I srvfile
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(often a file under
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.BR /srv )
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to connect to a remote file server.
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Exclusive with
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.BR -a .
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.TP
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.B k
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keep cache contents even if they might have come from a different server.
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.I Cfs
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will obey
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.B -r
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even if
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.B -k
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is given.
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.TP
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.B n
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mount the remote file server without authentication;
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often useful with
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.BR -F .
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.TP
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.B r
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reformat the cache disk partition.
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.TP
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.B s
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the connection to the remote file server is on file
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descriptors 0 and 1.
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.TP
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.B S
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turn on statistics gathering.  A file called
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.B cfsctl
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at the root of the caching file system can be read to get
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statistics concerning number of calls/bytes on client and server
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sides and latencies.
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.PP
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All 9P messages except
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.BR read ,
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.BR clone ,
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and
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.B walk
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(see
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.IR intro (5))
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are passed through
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.I cfs
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unchanged to the remote server.
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If possible, a
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.B read
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is satisfied by cached data.
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Otherwise, the file server is queried for any missing data.
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.SH FILES
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.TP
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.B /dev/sdC0/cache
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Default file used for storing cached data.
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.SH SOURCE
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.B /sys/src/cmd/cfs