Libguestfs is a library that can be linked with C and C++ management
programs (or management programs written in OCaml, Perl, Python, Ruby,
-Java, Haskell or C#). You can also use it from shell scripts or the
+Java, PHP, Haskell or C#). You can also use it from shell scripts or the
command line.
You don't need to be root to use libguestfs, although obviously you do
L</guestfs_list_partitions> and L</guestfs_lvs> to list possible
partitions and LVs, and either try mounting each to see what is
mountable, or else examine them with L</guestfs_vfs_type> or
-L</guestfs_file>. But you might find it easier to look at higher level
-programs built on top of libguestfs, in particular
-L<virt-inspector(1)>.
+L</guestfs_file>. Libguestfs also has a set of APIs for inspection of
+disk images (see L</INSPECTION> below). But you might find it easier
+to look at higher level programs built on top of libguestfs, in
+particular L<virt-inspector(1)>.
To mount a disk image read-only, use L</guestfs_mount_ro>. There are
several other variations of the C<guestfs_mount_*> call.
=head2 RUNNING COMMANDS
-Although libguestfs is a primarily an API for manipulating files
+Although libguestfs is primarily an API for manipulating files
inside guest images, we also provide some limited facilities for
running commands inside guests.
=item *
+The network may not be available unless you enable it
+(see L</guestfs_set_network>).
+
+=item *
+
Only supports Linux guests (not Windows, BSD, etc).
=item *
L</guestfs_luks_close> on the C</dev/mapper/mapname>
device (I<not> the underlying encrypted block device).
+=head2 INSPECTION
+
+Libguestfs has APIs for inspecting an unknown disk image to find out
+if it contains operating systems. (These APIs used to be in a
+separate Perl-only library called L<Sys::Guestfs::Lib(3)> but since
+version 1.5.3 the most frequently used part of this library has been
+rewritten in C and moved into the core code).
+
+Add all disks belonging to the unknown virtual machine and call
+L</guestfs_launch> in the usual way.
+
+Then call L</guestfs_inspect_os>. This function uses other libguestfs
+calls and certain heuristics, and returns a list of operating systems
+that were found. An empty list means none were found. A single
+element is the root filesystem of the operating system. For dual- or
+multi-boot guests, multiple roots can be returned, each one
+corresponding to a separate operating system. (Multi-boot virtual
+machines are extremely rare in the world of virtualization, but since
+this scenario can happen, we have built libguestfs to deal with it.)
+
+For each root, you can then call various C<guestfs_inspect_get_*>
+functions to get additional details about that operating system. For
+example, call L</guestfs_inspect_get_type> to return the string
+C<windows> or C<linux> for Windows and Linux-based operating systems
+respectively.
+
+Un*x-like and Linux-based operating systems usually consist of several
+filesystems which are mounted at boot time (for example, a separate
+boot partition mounted on C</boot>). The inspection rules are able to
+detect how filesystems correspond to mount points. Call
+C<guestfs_inspect_get_mountpoints> to get this mapping. It might
+return a hash table like this example:
+
+ /boot => /dev/sda1
+ / => /dev/vg_guest/lv_root
+ /usr => /dev/vg_guest/lv_usr
+
+The caller can then make calls to L</guestfs_mount_options> to
+mount the filesystems as suggested.
+
+Be careful to mount filesystems in the right order (eg. C</> before
+C</usr>). Sorting the keys of the hash by length, shortest first,
+should work.
+
+Inspection currently only works for some common operating systems.
+Contributors are welcome to send patches for other operating systems
+that we currently cannot detect.
+
+Encrypted disks must be opened before inspection. See
+L</ENCRYPTED DISKS> for more details. The L</guestfs_inspect_os>
+function just ignores any encrypted devices.
+
+A note on the implementation: The call L</guestfs_inspect_os> performs
+inspection and caches the results in the guest handle. Subsequent
+calls to C<guestfs_inspect_get_*> return this cached information, but
+I<do not> re-read the disks. If you change the content of the guest
+disks, you can redo inspection by calling L</guestfs_inspect_os>
+again.
+
=head2 SPECIAL CONSIDERATIONS FOR WINDOWS GUESTS
Libguestfs can mount NTFS partitions. It does this using the
Drive letter mappings are outside the scope of libguestfs. You have
to use libguestfs to read the appropriate Windows Registry and
configuration files, to determine yourself how drives are mapped (see
-also L<virt-inspector(1)>).
+also L<hivex(3)> and L<virt-inspector(1)>).
Replacing backslash characters with forward slash characters is also
outside the scope of libguestfs, but something that you can easily do.
For documentation see L<Sys::Guestfs(3)>.
+=item B<PHP>
+
+For documentation see C<README-PHP> supplied with libguestfs
+sources or in the php-libguestfs package for your distribution.
+
+The PHP binding only works correctly on 64 bit machines.
+
=item B<Python>
For documentation do:
This could be fixed in the generator by specially marking parameters
and return values which take bytes or other units.
-=item Protocol limit of 256 characters for error messages
-
-This limit is both rather small and quite unnecessary. We should be
-able to return error messages up to the length of the protocol message
-(2-4 MB).
-
-Note that we cannot change the protocol without some breakage, because
-there are distributions that repackage the Fedora appliance.
-
-=item Protocol should return errno with error messages.
+=item Library should return errno with error messages.
It would be a nice-to-have to be able to get the original value of
'errno' from inside the appliance along error paths (where set).
error message string into an errno, see the function error() in
fuse/guestmount.c.
+In libguestfs 1.5.4, the protocol was changed so that the
+Linux errno is sent back from the daemon.
+
=back
=head2 PROTOCOL LIMITS
=head2 guestfs_set_error_handler
typedef void (*guestfs_error_handler_cb) (guestfs_h *g,
- void *data,
+ void *opaque,
const char *msg);
void guestfs_set_error_handler (guestfs_h *g,
guestfs_error_handler_cb cb,
- void *data);
+ void *opaque);
The callback C<cb> will be called if there is an error. The
parameters passed to the callback are an opaque data pointer and the
=head2 guestfs_get_error_handler
guestfs_error_handler_cb guestfs_get_error_handler (guestfs_h *g,
- void **data_rtn);
+ void **opaque_rtn);
Returns the current error handler callback.
=head2 SINGLE CALLS AT COMPILE TIME
-If you need to test whether a single libguestfs function is
-available at compile time, we recommend using build tools
-such as autoconf or cmake. For example in autotools you could
-use:
+Since version 1.5.8, C<E<lt>guestfs.hE<gt>> defines symbols
+for each C API function, such as:
+
+ #define LIBGUESTFS_HAVE_DD 1
+
+if L</guestfs_dd> is available.
+
+Before version 1.5.8, if you needed to test whether a single
+libguestfs function is available at compile time, we recommended using
+build tools such as autoconf or cmake. For example in autotools you
+could use:
AC_CHECK_LIB([guestfs],[guestfs_create])
AC_CHECK_FUNCS([guestfs_dd])
at run time, as in this example program (note that you still
need the compile time check as well):
- #include <config.h>
-
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
main ()
{
- #ifdef HAVE_GUESTFS_DD
+ #ifdef LIBGUESTFS_HAVE_DD
void *dl;
int has_function;
Configuration commands for qemu such as L</guestfs_add_drive> can only
be issued when in the CONFIG state.
-The high-level API offers two calls that go from CONFIG through
-LAUNCHING to READY. L</guestfs_launch> blocks until the child process
-is READY to accept commands (or until some failure or timeout).
+The API offers one call that goes from CONFIG through LAUNCHING to
+READY. L</guestfs_launch> blocks until the child process is READY to
+accept commands (or until some failure or timeout).
L</guestfs_launch> internally moves the state from CONFIG to LAUNCHING
while it is running.
-High-level API actions such as L</guestfs_mount> can only be issued
-when in the READY state. These high-level API calls block waiting for
-the command to be carried out (ie. the state to transition to BUSY and
-then back to READY). But using the low-level event API, you get
-non-blocking versions. (But you can still only carry out one
-operation per handle at a time - that is a limitation of the
-communications protocol we use).
+API actions such as L</guestfs_mount> can only be issued when in the
+READY state. These API calls block waiting for the command to be
+carried out (ie. the state to transition to BUSY and then back to
+READY). There are no non-blocking versions, and no way to issue more
+than one command per handle at the same time.
Finally, the child process sends asynchronous messages back to the
-main program, such as kernel log messages. Mostly these are ignored
-by the high-level API, but using the low-level event API you can
-register to receive these messages.
+main program, such as kernel log messages. You can register a
+callback to receive these messages.
=head2 SETTING CALLBACKS TO HANDLE EVENTS
up by the time this is called, and if your callback then jumps
into some HLL function).
+=head2 guestfs_set_progress_callback
+
+ typedef void (*guestfs_progress_cb) (guestfs_h *g, void *opaque,
+ int proc_nr, int serial,
+ uint64_t position, uint64_t total);
+ void guestfs_set_progress_callback (guestfs_h *g,
+ guestfs_progress_cb cb,
+ void *opaque);
+
+Some long-running operations can generate progress messages. If
+this callback is registered, then it will be called each time a
+progress message is generated (usually two seconds after the
+operation started, and three times per second thereafter until
+it completes, although the frequency may change in future versions).
+
+The callback receives two numbers: C<position> and C<total>.
+The units of C<total> are not defined, although for some
+operations C<total> may relate in some way to the amount of
+data to be transferred (eg. in bytes or megabytes), and
+C<position> may be the portion which has been transferred.
+
+The only defined and stable parts of the API are:
+
+=over 4
+
+=item *
+
+The callback can display to the user some type of progress bar or
+indicator which shows the ratio of C<position>:C<total>.
+
+=item *
+
+0 E<lt>= C<position> E<lt>= C<total>
+
+=item *
+
+If any progress notification is sent during a call, then a final
+progress notification is always sent when C<position> = C<total>.
+
+This is to simplify caller code, so callers can easily set the
+progress indicator to "100%" at the end of the operation, without
+requiring special code to detect this case.
+
+=back
+
+The callback also receives the procedure number and serial number of
+the call. These are only useful for debugging protocol issues, and
+the callback can normally ignore them. The callback may want to
+print these numbers in error messages or debugging messages.
+
+=head1 PRIVATE DATA AREA
+
+You can attach named pieces of private data to the libguestfs handle,
+and fetch them by name for the lifetime of the handle. This is called
+the private data area and is only available from the C API.
+
+To attach a named piece of data, use the following call:
+
+ void guestfs_set_private (guestfs_h *g, const char *key, void *data);
+
+C<key> is the name to associate with this data, and C<data> is an
+arbitrary pointer (which can be C<NULL>). Any previous item with the
+same name is overwritten.
+
+You can use any C<key> you want, but names beginning with an
+underscore character are reserved for internal libguestfs purposes
+(for implementing language bindings). It is recommended to prefix the
+name with some unique string to avoid collisions with other users.
+
+To retrieve the pointer, use:
+
+ void *guestfs_get_private (guestfs_h *g, const char *key);
+
+This function returns C<NULL> if either no data is found associated
+with C<key>, or if the user previously set the C<key>'s C<data>
+pointer to C<NULL>.
+
+Libguestfs does not try to look at or interpret the C<data> pointer in
+any way. As far as libguestfs is concerned, it need not be a valid
+pointer at all. In particular, libguestfs does I<not> try to free the
+data when the handle is closed. If the data must be freed, then the
+caller must either free it before calling L</guestfs_close> or must
+set up a close callback to do it (see L</guestfs_set_close_callback>,
+and note that only one callback can be registered for a handle).
+
+The private data area is implemented using a hash table, and should be
+reasonably efficient for moderate numbers of keys.
+
=head1 BLOCK DEVICE NAMING
In the kernel there is now quite a profusion of schemata for naming
=head3 INITIAL MESSAGE
-Because the underlying channel (QEmu -net channel) doesn't have any
-sort of connection control, when the daemon launches it sends an
-initial word (C<GUESTFS_LAUNCH_FLAG>) which indicates that the guest
-and daemon is alive. This is what L</guestfs_launch> waits for.
+When the daemon launches it sends an initial word
+(C<GUESTFS_LAUNCH_FLAG>) which indicates that the guest and daemon is
+alive. This is what L</guestfs_launch> waits for.
+
+=head3 PROGRESS NOTIFICATION MESSAGES
+
+The daemon may send progress notification messages at any time. These
+are distinguished by the normal length word being replaced by
+C<GUESTFS_PROGRESS_FLAG>, followed by a fixed size progress message.
+
+The library turns them into progress callbacks (see
+C<guestfs_set_progress_callback>) if there is a callback registered,
+or discards them if not.
+
+The daemon self-limits the frequency of progress messages it sends
+(see C<daemon/proto.c:notify_progress>). Not all calls generate
+progress messages.
=head1 MULTIPLE HANDLES AND MULTIPLE THREADS
git.annexia.org / libguestfs.git / blobdiff