Implement 'dd' command.

[libguestfs.git] / guestfs.pod

diff --git a/guestfs.pod b/guestfs.pod
index 3aa806a..7b6a34e 100644 (file)
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -105,8 +105,8 @@ return error indications.
 =head2 DISK IMAGES
 
 The image filename (C<"guest.img"> in the example above) could be a
-disk image from a virtual machine, a L<dd(1)> copy of a physical block
-device, an actual block device, or simply an empty file of zeroes that
+disk image from a virtual machine, a L<dd(1)> copy of a physical hard
+disk, an actual block device, or simply an empty file of zeroes that
 you have created through L<posix_fallocate(3)>.  Libguestfs lets you
 do useful things to all of these.
 
@@ -142,7 +142,7 @@ first disk image that we added (C</dev/sda>).  If the disk contains
 Linux LVM2 logical volumes you could refer to those instead (eg. C</dev/VG/LV>).
 
 If you are given a disk image and you don't know what it contains then
-you have to find out.  Libguestfs can also do that: use
+you have to find out.  Libguestfs can do that too: use
 C<guestfs_list_partitions> and C<guestfs_lvs> to list possible
 partitions and LVs, and either try mounting each to see what is
 mountable, or else examine them with C<guestfs_file>.  But you might
@@ -274,6 +274,41 @@ non-portable between kernel versions, and they don't support labels or
 UUIDs.  If you want to pre-build an image or you need to mount it
 using a label or UUID, use an ISO image instead.
 
+=head2 COPYING
+
+There are various different commands for copying between files and
+devices and in and out of the guest filesystem.  These are summarised
+in the table below.
+
+=over 4
+
+=item B<file> to B<file>
+
+Use L</guestfs_cp> to copy a single file, or
+L</guestfs_cp_a> to copy directories recursively.
+
+=item B<file or device> to B<file or device>
+
+Use L</guestfs_dd> which efficiently uses L<dd(1)>
+to copy between files and devices in the guest.
+
+Example: duplicate the contents of an LV:
+
+ guestfs_dd (g, "/dev/VG/Original", "/dev/VG/Copy");
+
+The destination (C</dev/VG/Copy>) must be at least as large as the
+source (C</dev/VG/Original>).
+
+=item B<file on the host> to B<file or device>
+
+Use L</guestfs_upload>.  See L</UPLOADING> above.
+
+=item B<file or device> to B<file on the host>
+
+Use L</guestfs_download>.  See L</DOWNLOADING> above.
+
+=back
+
 =head2 LISTING FILES
 
 C<guestfs_ll> is just designed for humans to read (mainly when using
@@ -424,16 +459,26 @@ help on this issue.
 Although we don't want to discourage you from using the C API, we will
 mention here that the same API is also available in other languages.
 
-The API is broadly identical in all supported languages.  As an
-example, in Python the handle itself is replaced by an object, but we
-don't try to "object orientify" any other parts of the API.
+The API is broadly identical in all supported languages.  This means
+that the C call C<guestfs_mount(handle,path)> is
+C<$handle-E<gt>mount($path)> in Perl, C<handle.mount(path)> in Python,
+and C<Guestfs.mount handle path> in OCaml.  In other words, a
+straightforward, predictable isomorphism between each language.
+
+Error messages are automatically transformed
+into exceptions if the language supports it.
+
+We don't try to "object orientify" parts of the API in OO languages,
+although contributors are welcome to write higher level APIs above
+what we provide in their favourite languages if they wish.
 
 =over 4
 
 =item B<C++>
 
 You can use the I<guestfs.h> header file from C++ programs.  The C++
-API is identical to the C API.
+API is identical to the C API.  C++ classes and exceptions are
+not implemented.
 
 =item B<Haskell>
 
@@ -613,6 +658,13 @@ developer to program in confidence against libguestfs.
 
 @STRUCTS@
 
+=head1 AVAILABILITY
+
+Using L</guestfs_available> you can test availability of
+the following groups of functions:
+
+@AVAILABILITY@
+
 =head1 STATE MACHINE AND LOW-LEVEL EVENT API
 
 Internally, libguestfs is implemented by running a virtual machine