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+@c This is part of the paxutils manual.
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+@c Copyright (C) 2005 Free Software Foundation, Inc.
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+@c Written by Sergey Poznyakoff
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+@c This file is distributed under GFDL 1.1 or any later version
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+@c published by the Free Software Foundation.
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+
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+ A @dfn{snapshot file} (or @dfn{directory file}) is created during
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+incremental backups (@pxref{incremental and listed-incremental}). It
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+contains the status of the filesystem at the time of the dump and is
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+used to determine which files were modified since the last backup.
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+
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+ @GNUTAR{} version @value{VERSION} supports two snapshot file
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+formats. The first format, called @dfn{format 0}, is the one used by
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+@GNUTAR{} versions up to 1.15.1. The second format, called @dfn{format
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+1} is an extended version of this format, that contains more metadata
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+and allows for further extensions.
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+
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+ @samp{Format 0} snapshot file begins with a line containing a
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+decimal number that represents the UNIX timestamp of the beginning of
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+the last archivation. This line is followed by directory metadata
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+descriptions, one per line. Each description has the following format:
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+
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+@smallexample
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+[@var{nfs}]@var{dev} @var{inode} @var{name}
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+@end smallexample
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+
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+@noindent
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+where optional @var{nfs} is a single plus character (@samp{+}) if this
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+directory is located on an NFS-mounted partition, @var{dev} and
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+@var{inode} are the device and inode numbers of the directory, and
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+@var{name} is the directory name.
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+
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+ @samp{Format 1} snapshot file begins with a line specifying the
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+format of the file. This line has the following structure:
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+
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+@smallexample
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+@samp{GNU tar-}@var{tar-version}@samp{-}@var{incr-format-version}
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+@end smallexample
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+
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+@noindent
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+where @var{tar-version} is the version of @GNUTAR{} implementation
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+that created this snapshot, and @var{incr-format-version} is the
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+version number of the snapshot format (in this case @samp{1}).
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+
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+ The following line contains two decimal numbers, representing the
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+time of the last backup. First number is the number of seconds, the
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+second one is the number of nanoseconds, since the beginning of the
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+epoch.
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+
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+ Following lines contain directory metadate, one line per
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+directory. The line format is:
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+
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+@smallexample
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+[@var{nfs}]@var{mtime-sec} @var{mtime-nsec} @var{dev} @var{inode} @var{name}
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+@end smallexample
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+
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+@noindent
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+where @var{mtime-sec} and @var{mtime-nsec} represent the last
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+modification time of this directory with nanosecond precision;
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+@var{nfs}, @var{dev}, @var{inode} and @var{name} have the same meaning
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+as with @samp{format 0}.
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+
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+
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+@c End of snapshot.texi
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+
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+
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Sergey Poznyakoff