(tar)Adding to an Existing Archive

Updating an Archive

Creating a New Archive

Basic tar Operations

Adding to an Existing Archive
=============================

     *(This message will disappear, once this node revised.)*

   The `--append' (`-r') option will case `tar' to add new files to an
existing archive.  It interprets file names and member names in exactly
the same manner as `--create' (`-c').  Nothing happens if you don't
list any names.

   This option never deletes members.  If a new member is added under
the same name as an existing member, then both will be in the archive,
with the new member after the old one.  For information on how this
affects reading the archive,
FIXME: ref Multiple Members with the Same Name
   .

   This operation cannot be performed on some tape drives,
unfortunately, due to deficiencies in the formats thoes tape drives use.

   To add files to an archive, use `--append' (`-r').  The archive to
be added to must already exist and be in proper archive format (which
normally means it was created previously using `tar').  If the archive
was created with a different block size than now specified, `tar' will
report an error (
FIXME: pxref Blocking Factor
   ).  If the archive is not a valid `tar' archive, the results will be
unpredictable.  You cannot add files to a compressed archive, however
you can add files to the last volume of a multi-volume archive.

FIXME: xref Matching Format Parameters
   .

   The following example adds the file `shemp' to the archive `stooges'
created above:

     tar --append --file=stooges shemp

   You must specify the files to be added; there is no default.

   `--update' (`-u') acts like `--append' (`-r'), but does not add
files to the archive if there is already a file entry with that name in
the archive that has the same modification time.

   Both `--update' (`-u') and `--append' (`-r') work by adding to the
end of the archive.  When you extract a file from the archive, only the
version stored last will wind up in the file system.  Because
`--extract' (`-x') extracts files from an archive in sequence, and
overwrites files with the same name in the file system, if a file name
appears more than once in an archive the last version of the file will
overwrite the previous versions which have just been extracted.  You
should avoid storing older versions of a file later in the archive.

   Note:  `--update' (`-u') is not suitable for performing backups,
because it doesn't change directory content entries, and because it
lengthens the archive every time it is used.
FIXME: xref to scripted backup, listed incremental, for info on backups.