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.TH FOSSIL 4

.SH NAME

fossil, flchk, flfmt \- archival file server

.SH SYNOPSIS

.B fossil/fossil

[

.B -Dt

]

[

.B -c

.I cmd

]...

[

.B -f

.I file

]

[

.B -m

.I free-memory-percent

]

.PP

.B fossil/flchk

[

.B -f

]

[

.B -c

.I ncache

]

[

.B -h

.I host

]

.I file

.PP

.B fossil/flfmt

[

.B -y

]

[

.B -b

.I blocksize

]

[

.B -h

.I host

]

[

.B -l

.I label

]

[

.B -v

.I score

]

.I file

.PP

.B fossil/conf

[

.B -w

]

.I file

[

.I config

]

.PP

.B fossil/last

.I file

.SH DESCRIPTION

.I Fossil

is the main file system for Plan 9.

Unlike the Plan 9 file servers of old,

.I fossil

is a collection of user-space programs that run on a standard Plan 9 kernel.

The name of the main fossil file server at Murray Hill is

.BR pie .

The Plan 9 distribution file server,

.BR sources ,

is also a fossil server.

.PP

.I Fossil

is structured as a magnetic disk write buffer

optionally backed by a Venti server for archival storage.

It serves the Plan 9 protocol via TCP.

A

.I fossil

file server conventionally presents

three trees in the root directory of each file system:

.BR active ,

.BR archive ,

and

.BR snapshot .

.B /active

is the root of a conventional file system

whose blocks are stored in a disk file.

In a typical configuration, the file server periodically

marks the entire file system copy-on-write, effectively

taking a snapshot of the file system at that moment.

This snapshot is made available in a name

created from the date and time of the snapshot:

.BI /snapshot/ yyyy / mmdd / hhmm \fR,

where

.I yyyy

is the full year,

.I mm

is the month number,

.I dd

is the day number,

.I hh

is the hour,

and

.I mm

is the minute.

The snapshots in

.B /snapshot

are ephemeral: eventually they are deleted

to reclaim the disk space they occupy.

Long-lasting snapshots stored on a Venti server

are kept in 

.B /archive

and also named from the date (though not the time) of the snapshot:

.BI /archive/ yyyy / mmdds \fR,

where

.IR yyyy ,

.IR mm ,

and

.I dd

are year, month, and day as before,

and

.I s

is a sequence number if more than one

archival snapshot is done in a day.

For the first snapshot,

.I s

is null.

For the subsequent snapshots,

.I s

is

.BR .1 ,

.BR .2 ,

.BR .3 ,

etc.

The root of the main file system that is frozen

for the first archival snapshot of December 15, 2002

will be named

.BR /archive/2002/1215/ .

.PP

The attach name used in

.I mount

(see

.IR bind (1),

.IR bind (2)

and

.IR attach (5))

selects a file system to be served

and optionally a subtree,

in the format

.IB fs \fR[\fB/ dir \fR].

An empty attach name selects

.BR main/active .

.PP

.I Fossil

normally requires all users except

.L none

to provide authentication tickets on each

.IR attach (5).

To keep just anyone from connecting,

.L none

is only allowed to attach after another user

has successfully attached on the same

connection.

The other user effectively acts as a chaperone

for

.LR none .

Authentication can be disabled using the

.B -A

flag to

.B open

or

.B srv

(see

.IR fossilcons (8)).

.PP

The groups called

.B noworld

and

.B write

are special on the file server.

Any user belonging to

.B noworld

has attenuated access privileges.

Specifically, when checking such a user's access to files,

the file's permission bits are first ANDed

with 0770 for normal files and 0771 for directories.

The effect is to deny world access permissions to

.B noworld

users, except when walking into directories.

If the

.B write

group exists, then the file system appears read-only

to users not in the group.

This is used to make the Plan 9 distribution file server

.RI ( sources.cs.bell-labs.com )

readable by the world but writable only to the developers.

.PP

.I Fossil

starts a new instance of the fossil file server.

It is configured mainly through console commands,

documented in

.IR fossilcons (8).

.PP

The options are:

.TF "-c\fI cmd

.PD

.TP

.B -D

Toggle the debugging flag, which is initially off.

When the flag is set, information about authentication

and all protocol messages are written to standard error.

.TP

.B -t

Start a file server console on

.BR /dev/cons .

If this option is given,

.I fossil

does not fork itself into the background.

.TP

.BI -c " cmd

Execute the console command

.IR cmd .

This option may be repeated to give multiple

commands.

Typically the only commands given on the

command line are

.RB `` ".\fI file" ,''

which executes a file containing commands,

and

.RB `` "srv -p" \fIcons \fR,''

which starts a file server console on

.BI /srv/ cons \fR.

See

.IR fossilcons (8)

for more information.

.TP

.BI -f " file

Read and execute console commands stored in the Fossil disk 

.IR file .

.I Conf

.RI ( q.v. )

reads and writes the command set stored in the disk.

.TP

.B -m

Allocate

.I free-memory-percent

percent of the available free RAM for buffers.

This overrides all other memory sizing parameters,

notably the

.B -c

option to

.BR open .

30% is a reasonable choice.

.PD

.PP

.I Flchk

checks the fossil file system stored in

.I file

for inconsistencies.

.I Flchk

is deprecated in favor of the console

.B check

command (see

.IR fossilcons (8)).

.I Flchk

prints

.I fossil

console commands that may be

executed to take care of

bad pointers

.RB ( clrp ),

bad entries

.RB ( clre ),

bad directory entries

.RB ( clri ),

unreachable blocks

.RB ( bfree ).

Console commands are interspersed with

more detailed commentary on the file system.

The commands are distinguished by being prefixed with

sharp signs.

Note that all proposed fixes are rather drastic: offending

pieces of file system are simply chopped off.

.PP

.I Flchk

does

.I not

modify the file system, so it is safe to

run concurrently with

.IR fossil ,

though in this case

the list of unreachable

blocks and any inconsistencies involving the active file system

should be taken with a grain of salt.

.PP

The options are:

.TF "-h\fI host

.PD

.TP

.B -f

Fast mode.

By default,

.I flchk

checks the entire file system image for consistency,

which includes all the archives to Venti

and can take a very long time.

In fast mode,

.I flchk

avoids walking in Venti blocks

whenever possible.

.TP

.BI -c " ncache

Keep a cache of

.I ncache

(by default, 1000)

file system blocks in memory during the check.

.TP

.BI -h " host

Use

.I host

as the Venti server.

.PD

.PP

.I Flfmt

prepares

.I file

as a new fossil file system.

The file system is initialized with three empty directories

.BR active ,

.BR archive ,

and

.BR snapshot ,

as described above.

The options are:

.TF "-b\fI blocksize

.PD

.TP

.B -y

Yes mode.

By default,

.I flfmt

will prompt for confirmation before formatting

a file that already contains a fossil file system,

and before formatting a file that is not served

directly by a kernel device.

If the

.B -y

flag is given, no such checks are made.

.TP

.BI -b " blocksize

Set the file system block size (by default, 8192).

.TP

.BI -h " host

Use

.I host

as the Venti server.

.TP

.BI -l " label

Set the textual label on the file system to

.IR label .

The label is only a comment.

.TP

.BI -v " score

Initialize the file system using the vac file

system stored on Venti at

.IR score .

The score should have been generated by

.I fossil

rather than by

.IR vac (1),

so that the appropriate snapshot metadata is present.

.PD

.PP

.I Conf

reads or writes the configuration branded on the Fossil disk

.IR file .

By default, it reads the configuration from the disk and prints it to

standard output.

If the

.B -w

flag is given,

.I conf

reads a new configuration from 

.I config

(or else from standard input)

and writes it to the disk.

Inside the configuration file, the argument

.L *

may be used to stand in for the name of the disk holding the configuration.

The Plan 9 kernel boot process runs

.RB `` fossil

.B -f

.IR disk ''

to start a Fossil file server.

The disk is just a convenient place to store configuration

information.

.PP

.I Last

prints the vac score that resulted after the most recent archival snapshot 

of the fossil in

.I file.

.SH EXAMPLES

.PP

Place the root of the archive file system on

.B /n/dump

and show the modified times of the MIPS C compiler

over all dumps in December 2002:

.IP

.EX

9fs dump

ls -l /n/dump/2002/12*/mips/bin/vc

.EE

.PP

To get only one line of output for each version of the compiler:

.IP

.EX

ls -lp /n/dump/2002/12*/mips/bin/vc | uniq

.EE

.ne 14

.PP

Initialize a new file system, start the server with permission

checking turned off, create a users file, and mount the server:

.IP

.EX

fossil/flfmt /dev/sdC0/fossil

fossil/conf -w /dev/sdC0/fossil <<EOF

fsys main config

fsys main open -AWP

fsys main

create /active/adm adm sys d775

create /active/adm/users adm sys 664

users -w

srv -p fscons

srv fossil

EOF

fossil/fossil -f /dev/sdC0/fossil

mount /srv/fossil /n/fossil

.EE

.LP

See the discussion of the

.B users

and

.B uname

commands in

.IR fossilcons (8)

for more about the user table.

.ne 3

.PP

Perhaps because the disk has been corrupted or replaced,

format a new file system using the last archive score printed

on the console:

.IP

.EX

fossil/flfmt -v b9b3...5559 /dev/sdC0/fossil

.EE

.LP

Note that while

.B /snapshot

will be lost,

.B /active

and

.B /archive

will be restored to their contents at the time of the

last archival snapshot.

.ne 3

.PP

Blindly accept the changes prescribed by

.I flchk

(not recommended):

.IP

.EX

fossil/flchk /dev/sdC0/fossil | sed -n 's/^# //p' >>/srv/fscons

.EE

.LP

A better strategy is to vet the output,

filter out any suggestions you're not comfortable with,

and then use the

.I sed

command to prepare the script.

.SH SOURCE

.B /sys/src/cmd/fossil

.SH SEE ALSO

.IR yesterday (1),

.IR fs (3),

.IR fs (4),

.IR srv (4),

.IR fossilcons (8),

.IR loadfossil (8),

.IR venti (8)

.SH BUGS

It is possible that the disk format (but not the Venti format)

will change in the future, to make the disk a full cache

rather than just a write buffer.

Changing to the new format will require reformatting

the disk as in the example above,

but note that this will preserve most of the file system

(all but

.BR /snapshot )

with little effort.

.PP

The

.B -m

option currently assumes a block size of 8K bytes,

and a single file system per

.I fossil

instance.