tar.texi

来自「gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件」· TEXI 代码 · 共 1,767 行 · 第 1/5 页

* Device::                      Device selection and switching
* Remote Tape Server::
* Common Problems and Solutions::
* Blocking::                    Blocking
* Many::                        Many archives on one tape
* Using Multiple Tapes::        Using Multiple Tapes
* label::                       Including a Label in the Archive
* verify::
* Write Protection::

Blocking

* Format Variations::           Format Variations
* Blocking Factor::             The Blocking Factor of an Archive

Many Archives on One Tape

* Tape Positioning::            Tape Positions and Tape Marks
* mt::                          The @command{mt} Utility

Using Multiple Tapes

* Multi-Volume Archives::       Archives Longer than One Tape or Disk
* Tape Files::                  Tape Files
* Tarcat::                      Concatenate Volumes into a Single Archive


Tar Internals

* Standard::           Basic Tar Format
* Extensions::         @acronym{GNU} Extensions to the Archive Format
* Sparse Formats::     Storing Sparse Files
* Snapshot Files::
* Dumpdir::

Storing Sparse Files

* Old GNU Format::
* PAX 0::                PAX Format, Versions 0.0 and 0.1
* PAX 1::                PAX Format, Version 1.0

Genfile

* Generate Mode::     File Generation Mode.
* Status Mode::       File Status Mode.
* Exec Mode::         Synchronous Execution mode.

Copying This Manual

* GNU Free Documentation License::  License for copying this manual

@end detailmenu
@end menu

@node Introduction
@chapter Introduction

@GNUTAR{} creates
and manipulates @dfn{archives} which are actually collections of
many other files; the program provides users with an organized and
systematic method for controlling a large amount of data.
The name ``tar'' originally came from the phrase ``Tape ARchive'', but
archives need not (and these days, typically do not) reside on tapes.

@menu
* Book Contents::               What this Book Contains
* Definitions::                 Some Definitions
* What tar Does::               What @command{tar} Does
* Naming tar Archives::         How @command{tar} Archives are Named
* Authors::                     @GNUTAR{} Authors
* Reports::                     Reporting bugs or suggestions
@end menu

@node Book Contents
@section What this Book Contains

The first part of this chapter introduces you to various terms that will
recur throughout the book.  It also tells you who has worked on @GNUTAR{}
and its documentation, and where you should send bug reports
or comments.

The second chapter is a tutorial (@pxref{Tutorial}) which provides a
gentle introduction for people who are new to using @command{tar}.  It is
meant to be self contained, not requiring any reading from subsequent
chapters to make sense.  It moves from topic to topic in a logical,
progressive order, building on information already explained.

Although the tutorial is paced and structured to allow beginners to
learn how to use @command{tar}, it is not intended solely for beginners.
The tutorial explains how to use the three most frequently used
operations (@samp{create}, @samp{list}, and @samp{extract}) as well as
two frequently used options (@samp{file} and @samp{verbose}).  The other
chapters do not refer to the tutorial frequently; however, if a section
discusses something which is a complex variant of a basic concept, there
may be a cross reference to that basic concept.  (The entire book,
including the tutorial, assumes that the reader understands some basic
concepts of using a Unix-type operating system; @pxref{Tutorial}.)

The third chapter presents the remaining five operations, and
information about using @command{tar} options and option syntax.

The other chapters are meant to be used as a reference.  Each chapter
presents everything that needs to be said about a specific topic.

One of the chapters (@pxref{Date input formats}) exists in its
entirety in other @acronym{GNU} manuals, and is mostly self-contained.
In addition, one section of this manual (@pxref{Standard}) contains a
big quote which is taken directly from @command{tar} sources.

In general, we give both long and short (abbreviated) option names
at least once in each section where the relevant option is covered, so
that novice readers will become familiar with both styles.  (A few
options have no short versions, and the relevant sections will
indicate this.)

@node Definitions
@section Some Definitions

@cindex archive
@cindex tar archive
The @command{tar} program is used to create and manipulate @command{tar}
archives.  An @dfn{archive} is a single file which contains the contents
of many files, while still identifying the names of the files, their
owner(s), and so forth.  (In addition, archives record access
permissions, user and group, size in bytes, and data modification time.
Some archives also record the file names in each archived directory, as
well as other file and directory information.)  You can use @command{tar}
to @dfn{create} a new archive in a specified directory.

@cindex member
@cindex archive member
@cindex file name
@cindex member name
The files inside an archive are called @dfn{members}.  Within this
manual, we use the term @dfn{file} to refer only to files accessible in
the normal ways (by @command{ls}, @command{cat}, and so forth), and the term
@dfn{member} to refer only to the members of an archive.  Similarly, a
@dfn{file name} is the name of a file, as it resides in the file system,
and a @dfn{member name} is the name of an archive member within the
archive.

@cindex extraction
@cindex unpacking
The term @dfn{extraction} refers to the process of copying an archive
member (or multiple members) into a file in the file system.  Extracting
all the members of an archive is often called @dfn{extracting the
archive}.  The term @dfn{unpack} can also be used to refer to the
extraction of many or all the members of an archive.  Extracting an
archive does not destroy the archive's structure, just as creating an
archive does not destroy the copies of the files that exist outside of
the archive.  You may also @dfn{list} the members in a given archive
(this is often thought of as ``printing'' them to the standard output,
or the command line), or @dfn{append} members to a pre-existing archive.
All of these operations can be performed using @command{tar}.

@node What tar Does
@section What @command{tar} Does

@cindex tar
The @command{tar} program provides the ability to create @command{tar}
archives, as well as various other kinds of manipulation.  For example,
you can use @command{tar} on previously created archives to extract files,
to store additional files, or to update or list files which were already
stored.

Initially, @command{tar} archives were used to store files conveniently on
magnetic tape.  The name @command{tar} comes from this use; it stands for
@code{t}ape @code{ar}chiver.  Despite the utility's name, @command{tar} can
direct its output to available devices, files, or other programs (using
pipes).  @command{tar} may even access remote devices or files (as archives).

You can use @command{tar} archives in many ways.  We want to stress a few
of them: storage, backup, and transportation.

@FIXME{the following table entries need a bit of work.}
@table @asis
@item Storage
Often, @command{tar} archives are used to store related files for
convenient file transfer over a network.  For example, the
@acronym{GNU} Project distributes its software bundled into
@command{tar} archives, so that all the files relating to a particular
program (or set of related programs) can be transferred as a single
unit.

A magnetic tape can store several files in sequence.  However, the tape
has no names for these files; it only knows their relative position on
the tape.  One way to store several files on one tape and retain their
names is by creating a @command{tar} archive.  Even when the basic transfer
mechanism can keep track of names, as FTP can, the nuisance of handling
multiple files, directories, and multiple links makes @command{tar}
archives useful.

Archive files are also used for long-term storage.  You can think of
this as transportation from the present into the future.  (It is a
science-fiction idiom that you can move through time as well as in
space; the idea here is that @command{tar} can be used to move archives in
all dimensions, even time!)

@item Backup
Because the archive created by @command{tar} is capable of preserving
file information and directory structure, @command{tar} is commonly
used for performing full and incremental backups of disks.  A backup
puts a collection of files (possibly pertaining to many users and
projects) together on a disk or a tape.  This guards against
accidental destruction of the information in those files.
@GNUTAR{} has special features that allow it to be
used to make incremental and full dumps of all the files in a
file system.

@item Transportation
You can create an archive on one system, transfer it to another system,
and extract the contents there.  This allows you to transport a group of
files from one system to another.
@end table

@node Naming tar Archives
@section How @command{tar} Archives are Named

Conventionally, @command{tar} archives are given names ending with
@samp{.tar}.  This is not necessary for @command{tar} to operate properly,
but this manual follows that convention in order to accustom readers to
it and to make examples more clear.

@cindex tar file
@cindex entry
@cindex tar entry
Often, people refer to @command{tar} archives as ``@command{tar} files,'' and
archive members as ``files'' or ``entries''.  For people familiar with
the operation of @command{tar}, this causes no difficulty.  However, in
this manual, we consistently refer to ``archives'' and ``archive
members'' to make learning to use @command{tar} easier for novice users.

@node Authors
@section @GNUTAR{} Authors

@GNUTAR{} was originally written by John Gilmore,
and modified by many people.  The @acronym{GNU} enhancements were
written by Jay Fenlason, then Joy Kendall, and the whole package has
been further maintained by Thomas Bushnell, n/BSG, Fran@,{c}ois
Pinard, Paul Eggert, and finally Sergey Poznyakoff with the help of
numerous and kind users.

We wish to stress that @command{tar} is a collective work, and owes much to
all those people who reported problems, offered solutions and other
insights, or shared their thoughts and suggestions.  An impressive, yet
partial list of those contributors can be found in the @file{THANKS}
file from the @GNUTAR{} distribution.

@FIXME{i want all of these names mentioned, Absolutely.  BUT, i'm not
sure i want to spell out the history in this detail, at least not for
the printed book.  i'm just not sure it needs to be said this way.
i'll think about it.}

@FIXME{History is more important, and surely more interesting, than
actual names.  Quoting names without history would be meaningless.  FP}

Jay Fenlason put together a draft of a @GNUTAR{}
manual, borrowing notes from the original man page from John Gilmore.
This was withdrawn in version 1.11.  Thomas Bushnell, n/BSG and Amy
Gorin worked on a tutorial and manual for @GNUTAR{}.
Fran@,{c}ois Pinard put version 1.11.8 of the manual together by
taking information from all these sources and merging them.  Melissa
Weisshaus finally edited and redesigned the book to create version
1.12.  The book for versions from 1.14 up to @value{VERSION} were edited
by the current maintainer, Sergey Poznyakoff.

For version 1.12, Daniel Hagerty contributed a great deal of technical
consulting.  In particular, he is the primary author of @ref{Backups}.

In July, 2003 @GNUTAR{} was put on CVS at savannah.gnu.org
(see @url{http://savannah.gnu.org/projects/tar}), and
active development and maintenance work has started
again.  Currently @GNUTAR{} is being maintained by Paul Eggert, Sergey
Poznyakoff and Jeff Bailey.

Support for @acronym{POSIX} archives was added by Sergey Poznyakoff.

@node Reports
@section Reporting bugs or suggestions

@cindex bug reports
@cindex reporting bugs
If you find problems or have suggestions about this program or manual,
please report them to @file{bug-tar@@gnu.org}.

When reporting a bug, please be sure to include as much detail as
possible, in order to reproduce it.  @FIXME{Be more specific, I'd
like to make this node as detailed as 'Bug reporting' node in Emacs
manual}.

@node Tutorial
@chapter Tutorial Introduction to @command{tar}

This chapter guides you through some basic examples of three @command{tar}
operations: @option{--create}, @option{--list}, and @option{--extract}.  If
you already know how to use some other version of @command{tar}, then you
may not need to read this chapter.  This chapter omits most complicated
details about how @command{tar} works.

@menu
* assumptions::
* stylistic conventions::
* basic tar options::           Basic @command{tar} Operations and Options
* frequent operations::
* Two Frequent Options::
* create::                      How to Create Archives
* list::                        How to List Archives
* extract::                     How to Extract Members from an Archive
* going further::
@end menu

@node assumptions
@section Assumptions this Tutorial Makes

This chapter is paced to allow beginners to learn about @command{tar}
slowly.  At the same time, we will try to cover all the basic aspects of
these three operations.  In order to accomplish both of these tasks, we
have made certain assumptions about your knowledge before reading this
manual, and the hardware you will be using:

@itemize @bullet
@item
Before you start to work through this tutorial, you should understand
what the terms ``archive'' and ``archive member'' mean
(@pxref{Definitions}).  In addition, you should understand something
about how Unix-type operating systems work, and you should know how to
use some basic utilities.  For example, you should know how to create,
list, copy, rename, edit, and delete files and directories; how to
change between directories; and how to figure out where you are in the
file system.  You should have some basic understanding of directory
structure and how files are named according to which directory they are
in.  You should understand concepts such as standard output and standard
input, what various definitions of the term @samp{argument} mean, and the
differences between relative and absolute file names.  @FIXME{and what
else?}

@item
This manual assumes that you are working from your own home directory
(unless we state otherwise).  In this tutorial, you will create a
directory to practice @command{tar} commands in.  When we show file names,
we will assume that those names are relative to your home directory.
For example, my home directory is @file{/home/fsf/melissa}.  All of
my examples are in a subdirectory of the directory named by that file
name; the subdirectory is called @file{practice}.

@item
In general, we show examples of archives which exist on (or can be
written to, or worked with from) a directory on a hard disk.  In most
cases, you could write those archives to, or work with them on any other
device, such as a tape drive.  However, some of the later examples in
the tutorial and next chapter will not work on tape drives.
Additionally, working with tapes is much more complicated than working
with hard disks.  For these reasons, the tutorial does not cover working
with tape drives.  @xref{Media}, for complete information on using