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Sergey Poznyakoff
2006-05-25 14:12:35 +00:00
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@@ -474,11 +474,10 @@ magnetic tape. The name @command{tar} comes from this use; it stands for
direct its output to available devices, files, or other programs (using
pipes). @command{tar} may even access remote devices or files (as archives).
@FIXME{the following table entries need a bit of work..}
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
@@ -1215,13 +1214,11 @@ directory @file{.} to the archive, it notices that the file
it. (It makes no sense to put an archive into itself.) @GNUTAR{}
will continue in this case, and create the archive
normally, except for the exclusion of that one file. (@emph{Please
note:} Other versions of @command{tar} are not so clever; they will
enter an infinite loop when this happens, so you should not depend on
this behavior unless you are certain you are running @GNUTAR{}.)
@FIXME{bob doesn't like this sentence, since he does
it all the time, and we've been doing it in the editing passes for
this manual: In general, make sure that the archive is not inside a
directory being dumped.}
note:} Other implementations of @command{tar} may not be so clever;
they will enter an infinite loop when this happens, so you should not
depend on this behavior unless you are certain you are running
@GNUTAR{}. In general, it is wise to always place the archive outside
of the directory being dumped.
@node list
@section How to List Archives
@@ -1247,9 +1244,6 @@ folk
jazz
@end smallexample
@FIXME{we hope this will change. if it doesn't, need to show the
creation of bfiles somewhere above!!! : }
@noindent
The archive @file{bfiles.tar} would list as follows:
@@ -1260,17 +1254,18 @@ baboon
@end smallexample
@noindent
Be sure to use a @option{--file=@var{archive-name}} (@option{-f @var{archive-name}}) option just as with @option{--create} (@option{-c})
to specify the name of the archive.
Be sure to use a @option{--file=@var{archive-name}} (@option{-f
@var{archive-name}}) option just as with @option{--create}
(@option{-c}) to specify the name of the archive.
@opindex list, using with @option{--verbose}
@opindex verbose, using with @option{--list}
If you use the @option{--verbose} (@option{-v}) option with @option{--list}, then
@command{tar} will print out a listing reminiscent of @w{@samp{ls -l}},
showing owner, file size, and so forth.
If you use the @option{--verbose} (@option{-v}) option with
@option{--list}, then @command{tar} will print out a listing
reminiscent of @w{@samp{ls -l}}, showing owner, file size, and so forth.
If you had used @option{--verbose} (@option{-v}) mode, the example above would look
like:
If you had used @option{--verbose} (@option{-v}) mode, the example
above would look like:
@smallexample
$ @kbd{tar --list --verbose --file=collection.tar folk}
@@ -1451,12 +1446,13 @@ $ @kbd{tar --extract --file=collection.tar blues}
@noindent
If you list the files in the directory again, you will see that the file
@file{blues} has been restored, with its original permissions, data
modification times, and owner.@FIXME{This is only accidentally true, but not in
general. In most cases, one has to be root for restoring the owner, and
use a special option for restoring permissions. Here, it just happens
that the restoring user is also the owner of the archived members, and
that the current @code{umask} is compatible with original permissions.}
(These parameters will be identical to those which
modification times, and owner.@footnote{This is only accidentally
true, but not in general. Whereas modification times are always
restored, in most cases, one has to be root for restoring the owner,
and use a special option for restoring permissions. Here, it just
happens that the restoring user is also the owner of the archived
members, and that the current @code{umask} is compatible with original
permissions.} (These parameters will be identical to those which
the file had when you originally placed it in the archive; any changes
you may have made before deleting the file from the file system,
however, will @emph{not} have been made to the archive member.) The
@@ -1546,9 +1542,6 @@ file names of each of the files by archiving the @file{practice}
directory as @file{practice}, you must give @file{practice} as part
of the file names when you extract those files from the archive.
@FIXME{IMPORTANT! show the final structure, here. figure out what it
will be.}
@node extracting untrusted archives
@subsection Extracting Archives from Untrusted Sources
@@ -1956,8 +1949,6 @@ the same as the short option @option{-t}, and consequently, the same as the
mnemonic option @option{--list}. So for example, the command @w{@samp{tar
cv}} specifies the option @option{-v} in addition to the operation @option{-c}.
@FIXME{bob suggests having an uglier example. :-) }
When options that need arguments are given together with the command,
all the associated arguments follow, in the same order as the options.
Thus, the example given previously could also be written in the old
@@ -2008,8 +1999,6 @@ following are equivalent:
@kbd{tar cf archive.tar.gz -z file}
@end smallexample
@FIXME{still could explain this better; it's redundant:}
@cindex option syntax, traditional
As far as we know, all @command{tar} programs, @acronym{GNU} and
non-@acronym{GNU}, support old options. @GNUTAR{}
@@ -2176,13 +2165,9 @@ Lists the members in an archive. @xref{list}.
@item --update
@itemx -u
@FIXME{It was: A combination of the @option{--compare} and
@option{--append} operations. This is not true and rather misleading,
as @option{--compare} does a lot more than @option{--update} for
ensuring files are identical.} Adds files to the end of the archive,
but only if they are newer than their counterparts already in the
archive, or if they do not already exist in the archive.
@xref{update}.
Adds files to the end of the archive, but only if they are newer than
their counterparts already in the archive, or if they do not already
exist in the archive. @xref{update}.
@end table
@@ -3493,8 +3478,8 @@ The @option{--checkpoint} option prints an occasional message
as @command{tar} reads or writes the archive. In fact, it prints
a message each 10 records read or written. It is designed for
those who don't need the more detailed (and voluminous) output of
@option{--block-number} (@option{-R}), but do want visual confirmation that @command{tar}
is actually making forward progress.
@option{--block-number} (@option{-R}), but do want visual confirmation
that @command{tar} is actually making forward progress.
@FIXME{There is some confusion here. It seems that -R once wrote a
message at @samp{every} record read or written.}
@@ -3822,8 +3807,10 @@ and @ref{Media}, for more information.)
@cindex Archives, Appending files to
The simplest way to add a file to an already existing archive is the
@option{--append} (@option{-r}) operation, which writes specified files into the
archive whether or not they are already among the archived files.
@option{--append} (@option{-r}) operation, which writes specified
files into the archive whether or not they are already among the
archived files.
When you use @option{--append}, you @emph{must} specify file name
arguments, as there is no default. If you specify a file that already
exists in the archive, another copy of the file will be added to the
@@ -3859,30 +3846,21 @@ $ @kbd{tar --list --file=collection.tar}
-rw-r--r-- me user 20 1996-09-23 16:44 rock
@end smallexample
@FIXME{in theory, dan will (soon) try to turn this node into what it's
title claims it will become...}
@node multiple
@subsubsection Multiple Files with the Same Name
You can use @option{--append} (@option{-r}) to add copies of files which have been
updated since the archive was created. (However, we do not recommend
doing this since there is another @command{tar} option called
@option{--update}; @pxref{update} for more information. We describe this
use of @option{--append} here for the sake of completeness.) @FIXME{is
this really a good idea, to give this whole description for something
which i believe is basically a Stupid way of doing something? certain
aspects of it show ways in which tar is more broken than i'd personally
like to admit to, specifically the last sentence. On the other hand, i
don't think it's a good idea to be saying that we explicitly don't
recommend using something, but i can't see any better way to deal with
the situation.}When you extract the archive, the older version will be
effectively lost. This works because files are extracted from an
You can use @option{--append} (@option{-r}) to add copies of files
which have been updated since the archive was created. (However, we
do not recommend doing this since there is another @command{tar}
option called @option{--update}; @xref{update}, for more information.
We describe this use of @option{--append} here for the sake of
completeness.) When you extract the archive, the older version will
be effectively lost. This works because files are extracted from an
archive in the order in which they were archived. Thus, when the
archive is extracted, a file archived later in time will replace a
file of the same name which was archived earlier, even though the older
version of the file will remain in the archive unless you delete all
versions of the file.
file of the same name which was archived earlier, even though the
older version of the file will remain in the archive unless you delete
all versions of the file.
Supposing you change the file @file{blues} and then append the changed
version to @file{collection.tar}. As you saw above, the original
@@ -3968,20 +3946,20 @@ Same Name}
@node how to update
@subsubsection How to Update an Archive Using @option{--update}
You must use file name arguments with the @option{--update} (@option{-u}) operation.
If you don't specify any files, @command{tar} won't act on any files and
won't tell you that it didn't do anything (which may end up confusing
you).
You must use file name arguments with the @option{--update}
(@option{-u}) operation. If you don't specify any files,
@command{tar} won't act on any files and won't tell you that it didn't
do anything (which may end up confusing you).
@FIXME{note: the above parenthetical added because in fact, this
behavior just confused the author. :-) }
@c note: the above parenthetical added because in fact, this
@c behavior just confused the author. :-)
To see the @option{--update} option at work, create a new file,
@file{classical}, in your practice directory, and some extra text to the
file @file{blues}, using any text editor. Then invoke @command{tar} with
the @samp{update} operation and the @option{--verbose} (@option{-v}) option specified,
using the names of all the files in the practice directory as file name
arguments:
the @samp{update} operation and the @option{--verbose} (@option{-v})
option specified, using the names of all the files in the practice
directory as file name arguments:
@smallexample
$ @kbd{tar --update -v -f collection.tar blues folk rock classical}
@@ -4147,11 +4125,6 @@ blues
folk
jazz
rock
practice/blues
practice/folk
practice/jazz
practice/rock
practice/blues
$ @kbd{tar --delete --file=collection.tar blues}
$ @kbd{tar --list --file=collection.tar}
folk
@@ -4160,9 +4133,8 @@ rock
$
@end smallexample
@FIXME{I changed the order of these nodes around and haven't had a chance
to fix the above example's results, yet. I have to play with this and
follow it and see what it actually does!}
@FIXME{Check if the above listing is actually produced after running
all the examples on collection.tar.}
The @option{--delete} option has been reported to work properly when
@command{tar} acts as a filter from @code{stdin} to @code{stdout}.
@@ -4228,9 +4200,6 @@ Do not exit with nonzero on unreadable files or directories.
@section Options Used by @option{--extract}
@UNREVISED
@FIXME{i need to get dan to go over these options with me and see if
there's a better way of organizing them.}
@opindex extract, additional options
The previous chapter showed how to use @option{--extract} to extract
an archive into the file system. Various options cause @command{tar} to
@@ -4513,7 +4482,7 @@ Use in conjunction with @option{--extract} (@option{--get}, @option{-x}).
To set the modes (access permissions) of extracted files to those
recorded for those files in the archive, use @option{--same-permissions}
in conjunction with the @option{--extract} (@option{--get},
@option{-x}) operation. @FIXME{Should be aliased to ignore-umask.}
@option{-x}) operation.
@table @option
@opindex preserve-permission
@@ -4767,9 +4736,8 @@ option. This option is useful if you have set
@node remove files
@unnumberedsubsubsec Removing Files
@FIXME{the various macros in the front of the manual think that this
option goes in this section. i have no idea; i only know it's nowhere
else in the book...}
@FIXME{The section is too terse. Something more to add? An example,
maybe?}
@table @option
@opindex remove-files
@@ -5900,9 +5868,6 @@ This chapter discusses these options in detail.
@section Choosing and Naming Archive Files
@UNREVISED
@FIXME{should the title of this section actually be, "naming an
archive"?}
@cindex Naming an archive
@cindex Archive Name
@cindex Choosing an archive file
@@ -6066,8 +6031,8 @@ If you specify any other operation, @command{tar} does nothing.
By default, @command{tar} takes file names from the command line. However,
there are other ways to specify file or member names, or to modify the
manner in which @command{tar} selects the files or members upon which to
operate. @FIXME{add xref here}In general, these methods work both for
specifying the names of files and archive members.
operate. In general, these methods work both for specifying the names
of files and archive members.
@node files
@section Reading Names from a File
@@ -6630,20 +6595,19 @@ contents of the file were looked at).
Date specifiers can have embedded spaces. Because of this, you may need
to quote date arguments to keep the shell from parsing them as separate
arguments.
arguments. For example, the following command will add to the archive
all the files modified less than two days ago:
@FIXME{Need example of --newer-mtime with quoted argument.}
@smallexample
$ @kbd{tar -cf foo.tar --newer-mtime '2 days ago'}
@end smallexample
@quotation
@strong{Please Note:} @option{--after-date} and @option{--newer-mtime}
should not be used for incremental backups. Some files (such as those
in renamed directories) are not selected properly by these options.
@xref{Incremental Dumps}.
should not be used for incremental backups. @xref{Incremental Dumps},
for proper way of creating incremental backups.
@end quotation
@noindent
@FIXME{which tells -- need to fill this in!}
@node recurse
@section Descending into Directories
@UNREVISED
@@ -6654,8 +6618,6 @@ in renamed directories) are not selected properly by these options.
@FIXME{arrggh! this is still somewhat confusing to me. :-< }
@FIXME{show dan bob's comments, from 2-10-97}
Usually, @command{tar} will recursively explore all directories (either
those given on the command line or through the @option{--files-from}
option) for the various files they contain. However, you may not always
@@ -6667,7 +6629,7 @@ into specified directories. If you specify @option{--no-recursion}, you can
use the @command{find} utility for hunting through levels of directories to
construct a list of file names which you could then pass to @command{tar}.
@command{find} allows you to be more selective when choosing which files to
archive; see @ref{files} for more information on using @command{find} with
archive; see @ref{files}, for more information on using @command{find} with
@command{tar}, or look.
@table @option
@@ -6684,11 +6646,11 @@ When you use @option{--no-recursion}, @GNUTAR{} grabs
directory entries themselves, but does not descend on them
recursively. Many people use @command{find} for locating files they
want to back up, and since @command{tar} @emph{usually} recursively
descends on directories, they have to use the @samp{@w{! -d}} option
to @command{find} @FIXME{needs more explanation or a cite to another
info file}as they usually do not want all the files in a directory.
They then use the @option{--files-from} option to archive the files
located via @command{find}.
descends on directories, they have to use the @samp{@w{-not -type d}}
test in their @command{find} invocation (@pxref{Type, Type, Type test,
find, Finding Files}), as they usually do not want all the files in a
directory. They then use the @option{--files-from} option to archive
the files located via @command{find}.
The problem when restoring files archived in this manner is that the
directories themselves are not in the archive; so the
@@ -6696,7 +6658,15 @@ directories themselves are not in the archive; so the
@option{-p}) option does not affect them---while users might really
like it to. Specifying @option{--no-recursion} is a way to tell
@command{tar} to grab only the directory entries given to it, adding
no new files on its own.
no new files on its own. To summarize, if you use @command{find} to
create a list of files to be stored in an archive, use it as follows:
@smallexample
@group
$ @kbd{find @var{dir} @var{tests} | \
tar -cf @var{archive} -T - --no-recursion}
@end group
@end smallexample
The @option{--no-recursion} option also applies when extracting: it
causes @command{tar} to extract only the matched directory entries, not
@@ -6734,7 +6704,6 @@ or through @option{--files-from}, regardless of where they reside.
@table @option
@opindex one-file-system
@item --one-file-system
@itemx -l
Prevents @command{tar} from crossing file system boundaries when
archiving. Use in conjunction with any write operation.
@end table
@@ -6746,13 +6715,10 @@ a directory is not on the same file system as the directory itself, then
itself, @command{tar} will not archive anything beneath it; in other words,
@command{tar} will not cross mount points.
It is reported that using this option, the mount point is is archived,
but nothing under it.
This option is useful for making full or incremental archival backups of
a file system. If this option is used in conjunction with
@option{--verbose} (@option{-v}), files that are excluded are mentioned by name on the
standard error.
@option{--verbose} (@option{-v}), files that are excluded are
mentioned by name on the standard error.
@menu
* directory:: Changing Directory
@@ -6925,7 +6891,7 @@ ignoring leading slashes when extracting.
When you specify @option{--absolute-names} (@option{-P}),
@command{tar} stores file names including all superior directory
names, and preserves leading slashes. If you only invoked
names, and preserves leading slashes. If you only invoked
@command{tar} from the root directory you would never need the
@option{--absolute-names} option, but using this option
may be more convenient than switching to root.
@@ -6964,6 +6930,7 @@ For example:
@smallexample
$ @kbd{(cd / && tar -c -f archive.tar home)}
# @i{or}:
$ @kbd{tar -c -f archive.tar -C / home}
@end smallexample
@@ -7452,39 +7419,80 @@ the opposite, i.e., read the compressed data from the standard input
and produce uncompressed data on the standard output.
@end table
@FIXME{I have one question, or maybe it's a suggestion if there isn't a way
to do it now. I would like to use @option{--gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
to use :-)), basically adding ECC protection on top of compression.
It seems as if this should be quite easy to do, but I can't work out
exactly how to go about it. Of course, I can pipe the standard output
of @command{tar} through @command{ecc}, but then I lose (though I
haven't started using it yet, I confess) the ability to have
@command{tar} use @command{rmt} for it's I/O (I think).
@cindex gpg, using with tar
@cindex gnupg, using with tar
@cindex Using encrypted archives
The @option{--use-compress-program} option, in particular, lets you
implement your own filters, not necessarily dealing with
compression/decomression. For example, suppose you wish to implement
PGP encryption on top of compression, using @command{gpg} (@pxref{Top,
gpg, gpg ---- encryption and signing tool, gpg}). The following
script does that:
I think the most straightforward thing would be to let me specify a
general set of filters outboard of compression (preferably ordered,
so the order can be automatically reversed on input operations, and
with the options they require specifiable), but beggars shouldn't be
choosers and anything you decide on would be fine with me.
@smallexample
@group
#! /bin/sh
case $1 in
-d) gpg --decrypt - | gzip -d -c;;
'') gzip -c | gpg -s ;;
*) echo "Unknown option $1">&2; exit 1;;
esac
@end group
@end smallexample
By the way, I like @command{ecc} but if (as the comments say) it can't
deal with loss of block sync, I'm tempted to throw some time at adding
that capability. Supposing I were to actually do such a thing and
get it (apparently) working, do you accept contributed changes to
utilities like that? (Leigh Clayton @file{loc@@soliton.com}, May 1995).
Suppose you name it @file{gpgz} and save it somewhere in your
@env{PATH}. Then the following command will create a commpressed
archive signed with your private key:
Isn't that exactly the role of the @option{--use-compress-prog=@var{program}} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
@smallexample
$ @kbd{tar -cf foo.tar.gpgz --use-compress=gpgz .}
@end smallexample
It has been reported that if one writes compressed data (through the
@option{--gzip} or @option{--compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
end up with less space on the tape.}
@noindent
Likewise, the following command will list its contents:
@smallexample
$ @kbd{tar -tf foo.tar.gpgz --use-compress=gpgz .}
@end smallexample
@ignore
The above is based on the following discussion:
I have one question, or maybe it's a suggestion if there isn't a way
to do it now. I would like to use @option{--gzip}, but I'd also like
the output to be fed through a program like @acronym{GNU}
@command{ecc} (actually, right now that's @samp{exactly} what I'd like
to use :-)), basically adding ECC protection on top of compression.
It seems as if this should be quite easy to do, but I can't work out
exactly how to go about it. Of course, I can pipe the standard output
of @command{tar} through @command{ecc}, but then I lose (though I
haven't started using it yet, I confess) the ability to have
@command{tar} use @command{rmt} for it's I/O (I think).
I think the most straightforward thing would be to let me specify a
general set of filters outboard of compression (preferably ordered,
so the order can be automatically reversed on input operations, and
with the options they require specifiable), but beggars shouldn't be
choosers and anything you decide on would be fine with me.
By the way, I like @command{ecc} but if (as the comments say) it can't
deal with loss of block sync, I'm tempted to throw some time at adding
that capability. Supposing I were to actually do such a thing and
get it (apparently) working, do you accept contributed changes to
utilities like that? (Leigh Clayton @file{loc@@soliton.com}, May 1995).
Isn't that exactly the role of the
@option{--use-compress-prog=@var{program}} option?
I never tried it myself, but I suspect you may want to write a
@var{prog} script or program able to filter stdin to stdout to
way you want. It should recognize the @option{-d} option, for when
extraction is needed rather than creation.
It has been reported that if one writes compressed data (through the
@option{--gzip} or @option{--compress} options) to a DLT and tries to use
the DLT compression mode, the data will actually get bigger and one will
end up with less space on the tape.
@end ignore
@node sparse
@subsection Archiving Sparse Files
@@ -7548,7 +7556,7 @@ created in the future. If you use @option{--sparse} while making file
system backups as a matter of course, you can be assured the archive
will never take more space on the media than the files take on disk
(otherwise, archiving a disk filled with sparse files might take
hundreds of tapes). @FIXME-xref{incremental when node name is set.}
hundreds of tapes). @xref{Incremental Dumps}.
@end quotation
@command{tar} ignores the @option{--sparse} option when reading an archive.
@@ -7665,10 +7673,9 @@ files are easily and silently lost when files are given away.
When writing an archive, @command{tar} writes the user id and user name
separately. If it can't find a user name (because the user id is not
in @file{/etc/passwd}), then it does not write one. When restoring,
and doing a @code{chmod} like when you use @option{--same-permissions},
@FIXME{same-owner?}it tries to look the name (if one was written)
up in @file{/etc/passwd}. If it fails, then it uses the user id
stored in the archive instead.
it tries to look the name (if one was written) up in
@file{/etc/passwd}. If it fails, then it uses the user id stored in
the archive instead.
@opindex no-same-owner
@item --no-same-owner
@@ -7739,7 +7746,8 @@ Same as both @option{--same-permissions} and @option{--same-order}.
The @option{--preserve} option has no equivalent short option name.
It is equivalent to @option{--same-permissions} plus @option{--same-order}.
@FIXME{I do not see the purpose of such an option. (Neither I. FP.)}
@FIXME{I do not see the purpose of such an option. (Neither I. FP.)
Neither do I. --Sergey}
@end table