(tar.info.gz) Dealing with Old Files

Info Catalog

(tar.info.gz) Writing

(tar.info.gz) Overwrite Old Files

 
 Options Controlling the Overwriting of Existing Files
 .....................................................
 
 When extracting files, if 'tar' discovers that the extracted file
 already exists, it normally replaces the file by removing it before
 extracting it, to prevent confusion in the presence of hard or symbolic
 links.  (If the existing file is a symbolic link, it is removed, not
 followed.)  However, if a directory cannot be removed because it is
 nonempty, 'tar' normally overwrites its metadata (ownership, permission,
 etc.).  The '--overwrite-dir' option enables this default behavior.  To
 be more cautious and preserve the metadata of such a directory, use the
 '--no-overwrite-dir' option.
 
    To be even more cautious and prevent existing files from being
 replaced, use the '--keep-old-files' ('-k') option.  It causes 'tar' to
 refuse to replace or update a file that already exists, i.e., a file
 with the same name as an archive member prevents extraction of that
 archive member.  Instead, it reports an error.  For example:
 
      $ ls
      blues
      $ tar -x -k -f archive.tar
      tar: blues: Cannot open: File exists
      tar: Exiting with failure status due to previous errors
 
    If you wish to preserve old files untouched, but don't want 'tar' to
 treat them as errors, use the '--skip-old-files' option.  This option
 causes 'tar' to silently skip extracting over existing files.
 
    To be more aggressive about altering existing files, use the
 '--overwrite' option.  It causes 'tar' to overwrite existing files and
 to follow existing symbolic links when extracting.
 
    Some people argue that GNU 'tar' should not hesitate to overwrite
 files with other files when extracting.  When extracting a 'tar'
 archive, they expect to see a faithful copy of the state of the file
 system when the archive was created.  It is debatable that this would
 always be a proper behavior.  For example, suppose one has an archive in
 which 'usr/local' is a link to 'usr/local2'.  Since then, maybe the site
 removed the link and renamed the whole hierarchy from '/usr/local2' to
 '/usr/local'.  Such things happen all the time.  I guess it would not be
 welcome at all that GNU 'tar' removes the whole hierarchy just to make
 room for the link to be reinstated (unless it _also_ simultaneously
 restores the full '/usr/local2', of course!)  GNU 'tar' is indeed able
 to remove a whole hierarchy to reestablish a symbolic link, for example,
 but _only if_ '--recursive-unlink' is specified to allow this behavior.
 In any case, single files are silently removed.
 
    Finally, the '--unlink-first' ('-U') option can improve performance
 in some cases by causing 'tar' to remove files unconditionally before
 extracting them.
 

Info Catalog

(tar.info.gz) Writing

(tar.info.gz) Overwrite Old Files