S3QLCP(1)							       S3QL								 S3QLCP(1)

NAME

       s3qlcp - Copy-on-write replication on S3QL file systems

SYNOPSIS

       s3qlcp [options] <source-dir> <dest-dir>

DESCRIPTION

       S3QL  is  a  file  system for online data storage. Before using S3QL, make sure to consult the full documentation (rather than just the man
       pages which only briefly document the available userspace commands).

       The s3qlcp command duplicates the directory tree source-dir into dest-dir without physically copying the file contents.	 Both  source  and
       destination must lie inside the same S3QL file system.

       The replication will not take any additional space. Only if one of directories is modified later on, the modified data will take additional
       storage space.

       s3qlcp can only be called by the user that mounted the file system and (if the file system was mounted with --allow-other or  --allow-root)
       the root user. This limitation might be removed in the future (see issue 155).

       Note that:

       o After the replication, both source and target directory will still be completely ordinary directories. You can regard <src> as a snapshot
	 of <target> or vice versa. However, the most common usage of s3qlcp is to regularly duplicate the same source directory,  say	documents,
	 to  different	target	directories.  For a e.g. monthly replication, the target directories would typically be named something like docu-
	 ments_January for the replication in January, documents_February for the replication in February etc.	In this case it is clear that  the
	 target directories should be regarded as snapshots of the source directory.

       o Exactly  the  same  effect could be achieved by an ordinary copy program like cp -a. However, this procedure would be orders of magnitude
	 slower, because cp would have to read every file completely (so that S3QL had to fetch all the data over the network  from  the  backend)
	 before writing them into the destination folder.

   Snapshotting vs Hardlinking
       Snapshot  support in S3QL is inspired by the hardlinking feature that is offered by programs like rsync or storeBackup.	These programs can
       create a hardlink instead of copying a file if an identical file already exists in the backup. However, using hardlinks has two large  dis-
       advantages:

       o backups  and restores always have to be made with a special program that takes care of the hardlinking. The backup must not be touched by
	 any other programs (they may make changes that inadvertently affect other hardlinked files)

       o special care needs to be taken to handle files which are already hardlinked (the restore program needs to know that the hardlink was  not
	 just introduced by the backup program to safe space)

       S3QL snapshots do not have these problems, and they can be used with any backup program.

OPTIONS

       The s3qlcp command accepts the following options:

	  --debug
		 activate debugging output

	  --quiet
		 be really quiet

	  --version
		 just print program version and exit

EXIT STATUS

       s3qlcp returns exit code 0 if the operation succeeded and 1 if some error occurred.

SEE ALSO

       The S3QL homepage is at http://code.google.com/p/s3ql/.

       The   full  S3QL  documentation	should	also  be  installed  somewhere	on  your  system,  common  locations  are  /usr/share/doc/s3ql	or
       /usr/local/doc/s3ql.

COPYRIGHT

       2008-2011, Nikolaus Rath

1.11.1								  August 27, 2014							 S3QLCP(1)