=head1 SYNOPSIS
- guestfs_h handle = guestfs_create ();
+ #include <guestfs.h>
+
+ guestfs_h *handle = guestfs_create ();
guestfs_add_drive (handle, "guest.img");
guestfs_launch (handle);
guestfs_wait_ready (handle);
guestfs_mount (handle, "/dev/sda1", "/");
- guestfs_touch_file (handle, "/hello");
+ guestfs_touch (handle, "/hello");
guestfs_sync (handle);
guestfs_close (handle);
Libguestfs provides ways to enumerate guest storage (eg. partitions,
LVs, what filesystem is in each LV, etc.). It can also run commands
-in the context of the guest. Also you can mount guest filesystems on
-the host (requires root privs and NFS).
+in the context of the guest. Also you can access filesystems over FTP.
Libguestfs is a library that can be linked with C and C++ management
-programs (or management programs written in other languages, if people
-contribute the language bindings). You can also use it from shell
-scripts or the command line.
+programs (or management programs written in OCaml, Perl or Python).
+You can also use it from shell scripts or the command line.
-=head1 CONNECTION MANAGEMENT
+You don't need to be root to use libguestfs, although obviously you do
+need enough permissions to access the disk images.
+=head1 CONNECTION MANAGEMENT
+If you are using the high-level API, then you should call the
+functions in the following order:
+ guestfs_h *handle = guestfs_create ();
+
+ guestfs_add_drive (handle, "guest.img");
+ /* call guestfs_add_drive additional times if the guest has
+ * multiple disks
+ */
+
+ guestfs_launch (handle);
+ guestfs_wait_ready (handle);
+ /* now you can examine what partitions, LVs etc are available
+ * you have to mount / at least
+ */
+ guestfs_mount (handle, "/dev/sda1", "/");
+ /* now you can perform actions on the guest disk image */
+ guestfs_touch (handle, "/hello");
+
+ /* you only need to call guestfs_sync if you have made
+ * changes to the guest image
+ */
+ guestfs_sync (handle);
+
+ guestfs_close (handle);
-=head1 CONFIGURATION MANAGEMENT
+C<guestfs_wait_ready> and all of the actions including C<guestfs_sync>
+are blocking calls. You can use the low-level event API to do
+non-blocking operations instead.
+All functions that return integers, return C<-1> on error. See
+section ERROR HANDLING below for how to handle errors.
+=head2 guestfs_h *
+C<guestfs_h> is the opaque type representing a connection handle.
+Create a handle by calling C<guestfs_create>. Call C<guestfs_close>
+to free the handle and release all resources used.
+Handles and operations on handles are not thread safe. However you
+can use a separate handle for each thread (but not on the same disk
+image).
+=head2 guestfs_create
-=head1 HIGH-LEVEL API
+ guestfs_h *guestfs_create (void);
+Create a connection handle.
+You have to call C<guestfs_add_drive> on the handle at least once.
+This function returns a non-NULL pointer to a handle on success or
+NULL on error.
+After configuring the handle, you have to call C<guestfs_launch> and
+C<guestfs_wait_ready>.
+You may also want to configure error handling for the handle. See
+ERROR HANDLING section below.
+=head2 guestfs_close
+ void guestfs_close (guestfs_h *handle);
+This closes the connection handle and frees up all resources used.
=head1 ERROR HANDLING
+The convention in all functions that return C<int> is that they return
+C<-1> to indicate an error. You can get additional information on
+errors by calling C<guestfs_last_error> and/or by setting up an error
+handler with C<guestfs_set_error_handler>.
+
+The default error handler prints the information string to C<stderr>.
+
+Out of memory errors are handled differently. The default action is
+to call L<abort(3)>. If this is undesirable, then you can set a
+handler using C<guestfs_set_out_of_memory_handler>.
+
+=head2 guestfs_last_error
+
+ const char *guestfs_last_error (guestfs_h *handle);
+
+This returns the last error message that happened on C<handle>. If
+there has not been an error since the handle was created, then this
+returns C<NULL>.
+
+The lifetime of the returned string is until the next error occurs, or
+C<guestfs_close> is called.
+
+The error string is not localized (ie. is always in English), because
+this makes searching for error messages in search engines give the
+largest number of results.
+
+=head2 guestfs_set_error_handler
+
+ typedef void (*guestfs_error_handler_cb) (guestfs_h *handle,
+ void *data,
+ const char *msg);
+ void guestfs_set_error_handler (guestfs_h *handle,
+ guestfs_error_handler_cb cb,
+ void *data);
+
+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
+error message string.
+
+Note that the message string C<msg> is freed as soon as the callback
+function returns, so if you want to stash it somewhere you must make
+your own copy.
+
+The default handler prints messages on C<stderr>.
+
+If you set C<cb> to C<NULL> then I<no> handler is called.
+=head2 guestfs_get_error_handler
+ guestfs_error_handler_cb guestfs_get_error_handler (guestfs_h *handle,
+ void **data_rtn);
+Returns the current error handler callback.
+=head2 guestfs_set_out_of_memory_handler
+
+ typedef void (*guestfs_abort_cb) (void);
+ int guestfs_set_out_of_memory_handler (guestfs_h *handle,
+ guestfs_abort_cb);
+
+The callback C<cb> will be called if there is an out of memory
+situation. I<Note this callback must not return>.
+
+The default is to call L<abort(3)>.
+
+You cannot set C<cb> to C<NULL>. You can't ignore out of memory
+situations.
+
+=head2 guestfs_get_out_of_memory_handler
+
+ guestfs_abort_fn guestfs_get_out_of_memory_handler (guestfs_h *handle);
+
+This returns the current out of memory handler.
+
+=head1 PATH
+
+Libguestfs needs a kernel and initrd.img, which it finds by looking
+along an internal path.
+
+By default it looks for these in the directory C<$libdir/guestfs>
+(eg. C</usr/local/lib/guestfs> or C</usr/lib64/guestfs>).
+
+Use C<guestfs_set_path> or set the environment variable
+C<LIBGUESTFS_PATH> to change the directories that libguestfs will
+search in. The value is a colon-separated list of paths. The current
+directory is I<not> searched unless the path contains an empty element
+or C<.>. For example C<LIBGUESTFS_PATH=:/usr/lib/guestfs> would
+search the current directory and then C</usr/lib/guestfs>.
+
+=head1 HIGH-LEVEL API ACTIONS
+
+@ACTIONS@
+
+=head1 STRUCTURES
+
+@STRUCTS@
=head1 STATE MACHINE AND LOW-LEVEL EVENT API
that the complexity is dealing with the (asynchronous) actions of the
child process.
+ child process
+ ___________________ _________________________
+ / \ / \
+ | main program | | qemu +-----------------+|
+ | | | | Linux kernel ||
+ +-------------------+ | +-----------------+|
+ | libguestfs <-------------->| guestfsd ||
+ | | | +-----------------+|
+ \___________________/ \_________________________/
+
+The diagram above shows libguestfs communicating with the guestfsd
+daemon running inside the qemu child process. There are several
+points of failure here: qemu can fail to start, the virtual machine
+inside qemu can fail to boot, guestfsd can fail to start or not
+establish communication, any component can start successfully but fail
+asynchronously later, and so on.
+
=head2 STATE MACHINE
libguestfs uses a state machine to model the child process:
=head2 NON-BLOCKING ACTIONS
+XXX NOT IMPLEMENTED YET XXX
+
C<guestfs_set_reply_callback> is the most interesting callback to
play with, since it allows you to perform actions without blocking.
/* returns immediately */
}
- my_cb (guestfs_h handle, void *data)
+ my_cb (guestfs_h *handle, void *data, XDR *xdr)
{
- retval = guestfs_nb_[action]_r (handle);
+ retval = guestfs_nb_[action]_r (handle, xdr);
/* ... */
}
There are C<guestfs_nb_*> and C<guestfs_nb_*_r> functions
-corresponding to (very nearly) every C<guestfs_*> action in the
-high-level API.
+corresponding to every C<guestfs_*> action in the high-level API.
=head2 guestfs_set_reply_callback
- void guestfs_set_reply_callback (guestfs_handle h,
+ typedef void (*guestfs_reply_cb) (guestfs_h *g, void *opaque, XDR *xdr);
+ void guestfs_set_reply_callback (guestfs_h *handle,
guestfs_reply_cb cb,
void *opaque);
received from the child process. (This corresponds to a transition
from the BUSY state to the READY state).
-Note (I<important!>) that high-level API calls overwrite this
-callback.
+Note that the C<xdr> that you get in the callback is in C<XDR_DECODE>
+mode, and you need to consume it before you return from the callback
+function (since it gets destroyed after).
=head2 guestfs_set_log_message_callback
- void guestfs_set_log_message_callback (guestfs_handle h,
+ typedef void (*guestfs_log_message_cb) (guestfs_h *g, void *opaque,
+ char *buf, int len);
+ void guestfs_set_log_message_callback (guestfs_h *handle,
guestfs_log_message_cb cb,
void *opaque);
=head2 guestfs_set_subprocess_quit_callback
- void guestfs_set_subprocess_quit_callback (guestfs_handle h,
+ typedef void (*guestfs_subprocess_quit_cb) (guestfs_h *g, void *opaque);
+ void guestfs_set_subprocess_quit_callback (guestfs_h *handle,
guestfs_subprocess_quit_cb cb,
void *opaque);
C<guestfs_kill_subprocess>. (This corresponds to a transition from
any state to the CONFIG state).
-=head2 guestfs_set_ready_callback
+=head2 guestfs_set_launch_done_callback
- void guestfs_set_ready_callback (guestfs_handle h,
- guestfs_ready_cb cb,
- void *opaque);
+ typedef void (*guestfs_launch_done_cb) (guestfs_h *g, void *opaque);
+ void guestfs_set_launch_done_callback (guestfs_h *handle,
+ guestfs_ready_cb cb,
+ void *opaque);
The callback function C<cb> will be called when the child process
-becomes ready. (This corresponds to a transition from I<either>
-LAUNCHING I<or> BUSY to the READY state).
+becomes ready first time after it has been launched. (This
+corresponds to a transition from LAUNCHING to the READY state).
You can use this instead of C<guestfs_wait_ready> to implement a
non-blocking wait for the child process to finish booting up.
=over 4
-=item libguestfs-poll
+=item libguestfs-select
-A simple main loop that is implemented using L<poll(2)>.
+A simple main loop that is implemented using L<select(2)>.
This is the default main loop unless you call C<guestfs_set_main_loop>
or C<guestfs_glib_set_main_loop>.
=head2 WRITING A CUSTOM MAIN LOOP
-This isn't documented. Please see the libguestfs-poll and libguestfs-glib
-implementations.
+This isn't documented. Please see the libguestfs-select and
+libguestfs-glib implementations.
-=head1 SEE ALSO
+=head1 ENVIRONMENT VARIABLES
-L<qemu(1)>
+=over 4
+
+=item LIBGUESTFS_DEBUG
+
+Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages. This
+has the same effect as calling C<guestfs_set_verbose (handle, 1)>.
+=item LIBGUESTFS_PATH
+Set the path that libguestfs uses to search for kernel and initrd.img.
+See the discussion of paths in section PATH above.
+=back
+
+=head1 SEE ALSO
+L<guestfish(1)>,
+L<qemu(1)>,
+L<febootstrap(1)>,
+L<http://et.redhat.com/~rjones/libguestfs>.
=head1 AUTHORS
git.annexia.org / libguestfs.git / blobdiff