incremental backup using tar

[Root Boy Jim]

   From: Dennis John Linse <djlinse at phoenix.Princeton.EDU>

   Last night I was trying to figure out how to due an incremental backup
   on a Silicon Graphics Iris running System V.  The manual suggested using

   find . -mtime -7 -print | tar c -

   The problem I encountered was that the find command finds all of the
   directories along the way.  For example the output of find might be

	./bin
	./bin/foo

   where foo is a file to be backed up.  When tar gets this, it recursively
   backs up the entire bin directory.  After much work, I came up with the
   command

   find . \( -mtime -7 -exec test -f {} \; -print \) | tar c -

   which seems to due the trick.

Right idea, but see below.

   The questions I have are

   1) Is this the best way or is there a better one?

Replace "-exec test -f {} \;" with "-type f".

   2) Does the resulting archive have the necessary directory information
      to recreate the files in the event that they are needed?
      Specifically, if a directory doesn't exist when the archive is read
      back in, will it be created properly?

Yes. Tar creates directorys, but does not restore their modification
time correctly. Additionally, the owner/group/mode will not necessarily
be set correctly if the directory does not exist when restoring it.

Additionally, symbolic links may give you trouble. Perhaps you might
want "! -type d" instead of "-type f".

You may also want to add a "| fgrep -v -f filesnotosave |" between the
find and the tar.

   Dennis

	(Root Boy) Jim Cottrell	<rbj at icst-cmr.arpa>
	National Bureau of Standards
	Flamer's Hotline: (301) 975-5688
	The opinions expressed are solely my own
	and do not reflect NBS policy or agreement
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