tar will normally automatically cross file system boundaries in
order to archive files which are part of a directory tree. You can
change this behavior by running tar and specifying
--one-file-system (-l). This option only affects files that are
archived because they are in a directory that is being archived;
tar will still archive files explicitly named on the command line
or through --files-from, regardless of where they reside.
--one-file-system
-l
Prevents tar from crossing file system boundaries when
archiving. Use in conjunction with any write operation.
The --one-file-system option causes tar to modify its
normal behavior in archiving the contents of directories. If a file in
a directory is not on the same file system as the directory itself, then
tar will not archive that file. If the file is a directory
itself, tar will not archive anything beneath it; in other words,
tar will not cross mount points.
It is reported that using this option, the mount point is is archived,
but nothing under it.
This option is useful for making full or incremental archival backups of
a file system. If this option is used in conjunction with
--verbose (-v), files that are excluded are mentioned by name on the
standard error.
