Libguestfs is a library that can be linked with C and C++ management
programs (or management programs written in OCaml, Perl, Python, Ruby,
-Java, PHP, Haskell or C#). You can also use it from shell scripts or the
-command line.
+Java, PHP, Erlang, 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
need enough permissions to access the disk images.
The C# bindings are highly experimental. Please read the warnings
at the top of C<csharp/Libguestfs.cs>.
+=item B<Erlang>
+
+See L<guestfs-erlang(3)>.
+
=item B<Haskell>
This is the only language binding that is working but incomplete.
=item B<Java>
Full documentation is contained in the Javadoc which is distributed
-with libguestfs.
+with libguestfs. For examples, see L<guestfs-java(3)>.
=item B<OCaml>
For other programs the caller will almost certainly want to install an
alternate error handler or do error handling in-line like this:
- g = guestfs_create ();
-
/* This disables the default behaviour of printing errors
on stderr. */
guestfs_set_error_handler (g, NULL, NULL);
/* Examine the error message and print it etc. */
char *msg = guestfs_last_error (g);
int errnum = guestfs_last_errno (g);
- fprintf (stderr, "%s\n", msg);
+ fprintf (stderr, "%s", msg);
+ if (errnum != 0)
+ fprintf (stderr, ": %s", strerror (errnum));
+ fprintf (stderr, "\n");
/* ... */
- }
+ }
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
=head2 guestfs_set_out_of_memory_handler
typedef void (*guestfs_abort_cb) (void);
- int guestfs_set_out_of_memory_handler (guestfs_h *g,
- guestfs_abort_cb);
+ void guestfs_set_out_of_memory_handler (guestfs_h *g,
+ 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>.
can override the printing of trace messages to stderr by setting up a
callback.
+=item GUESTFS_EVENT_ENTER
+(payload type: function name)
+
+The callback function is called whenever a libguestfs function
+is entered.
+
+The payload is a string which contains the name of the function
+that we are entering (not including C<guestfs_> prefix).
+
+Note that libguestfs functions can call themselves, so you may
+see many events from a single call. A few libguestfs functions
+do not generate this event.
+
+If no callback is registered: the event is ignored.
+
=back
=head3 guestfs_set_event_callback
syslog (priority, "event 0x%lx: %s", event, buf);
}
+=head1 CANCELLING LONG TRANSFERS
+
+Some operations can be cancelled by the caller while they are in
+progress. Currently only operations that involve uploading or
+downloading data can be cancelled (technically: operations that have
+C<FileIn> or C<FileOut> parameters in the generator).
+
+=head2 guestfs_user_cancel
+
+ void guestfs_user_cancel (guestfs_h *g);
+
+C<guestfs_user_cancel> cancels the current upload or download
+operation.
+
+Unlike most other libguestfs calls, this function is signal safe and
+thread safe. You can call it from a signal handler or from another
+thread, without needing to do any locking.
+
+The transfer that was in progress (if there is one) will stop shortly
+afterwards, and will return an error. The errno (see
+L</guestfs_last_errno>) is set to C<EINTR>, so you can test for this
+to find out if the operation was cancelled or failed because of
+another error.
+
+No cleanup is performed: for example, if a file was being uploaded
+then after cancellation there may be a partially uploaded file. It is
+the caller's responsibility to clean up if necessary.
+
+There are two common places that you might call C<guestfs_user_cancel>.
+
+In an interactive text-based program, you might call it from a
+C<SIGINT> signal handler so that pressing C<^C> cancels the current
+operation. (You also need to call L</guestfs_set_pgroup> so that
+child processes don't receive the C<^C> signal).
+
+In a graphical program, when the main thread is displaying a progress
+bar with a cancel button, wire up the cancel button to call this
+function.
+
=head1 PRIVATE DATA AREA
You can attach named pieces of private data to the libguestfs handle,
=head1 INTERNALS
+=head2 APPLIANCE BOOT PROCESS
+
+This process has evolved and continues to evolve. The description
+here corresponds only to the current version of libguestfs and is
+provided for information only.
+
+In order to follow the stages involved below, enable libguestfs
+debugging (set the environment variable C<LIBGUESTFS_DEBUG=1>).
+
+=over 4
+
+=item Create the appliance
+
+C<febootstrap-supermin-helper> is invoked to create the kernel, a
+small initrd and the appliance.
+
+The appliance is cached in C</var/tmp/.guestfs-E<lt>UIDE<gt>> (or in
+another directory if C<TMPDIR> is set).
+
+For a complete description of how the appliance is created and cached,
+read the L<febootstrap(8)> and L<febootstrap-supermin-helper(8)> man
+pages.
+
+=item Start qemu and boot the kernel
+
+qemu is invoked to boot the kernel.
+
+=item Run the initrd
+
+C<febootstrap-supermin-helper> builds a small initrd. The initrd is
+not the appliance. The purpose of the initrd is to load enough kernel
+modules in order that the appliance itself can be mounted and started.
+
+The initrd is a cpio archive called
+C</var/tmp/.guestfs-E<lt>UIDE<gt>/initrd>.
+
+When the initrd has started you will see messages showing that kernel
+modules are being loaded, similar to this:
+
+ febootstrap: ext2 mini initrd starting up
+ febootstrap: mounting /sys
+ febootstrap: internal insmod libcrc32c.ko
+ febootstrap: internal insmod crc32c-intel.ko
+
+=item Find and mount the appliance device
+
+The appliance is a sparse file containing an ext2 filesystem which
+contains a familiar (although reduced in size) Linux operating system.
+It would normally be called C</var/tmp/.guestfs-E<lt>UIDE<gt>/root>.
+
+The regular disks being inspected by libguestfs are the first
+devices exposed by qemu (eg. as C</dev/vda>).
+
+The last disk added to qemu is the appliance itself (eg. C</dev/vdb>
+if there was only one regular disk).
+
+Thus the final job of the initrd is to locate the appliance disk,
+mount it, and switch root into the appliance, and run C</init> from
+the appliance.
+
+If this works successfully you will see messages such as:
+
+ febootstrap: picked /sys/block/vdb/dev as root device
+ febootstrap: creating /dev/root as block special 252:16
+ febootstrap: mounting new root on /root
+ febootstrap: chroot
+ Starting /init script ...
+
+Note that C<Starting /init script ...> indicates that the appliance's
+init script is now running.
+
+=item Initialize the appliance
+
+The appliance itself now initializes itself. This involves starting
+certain processes like C<udev>, possibly printing some debug
+information, and finally running the daemon (C<guestfsd>).
+
+=item The daemon
+
+Finally the daemon (C<guestfsd>) runs inside the appliance. If it
+runs you should see:
+
+ verbose daemon enabled
+
+The daemon expects to see a named virtio-serial port exposed by qemu
+and connected on the other end to the library.
+
+The daemon connects to this port (and hence to the library) and sends
+a four byte message C<GUESTFS_LAUNCH_FLAG>, which initiates the
+communication protocol (see below).
+
+=back
+
=head2 COMMUNICATION PROTOCOL
Don't rely on using this protocol directly. This section documents
The L<virt-cat(1)>, L<virt-filesystems(1)> and L<virt-ls(1)> commands
and documentation.
+=item C<caution>
+
+Safety and liveness tests of components that libguestfs depends upon
+(not of libguestfs itself). Mainly this is for qemu and the kernel.
+
=item C<contrib>
Outside contributions, experimental parts.
L<virt-df(1)> command and documentation.
+=item C<edit>
+
+L<virt-edit(1)> command and documentation.
+
=item C<examples>
C API example code.
=item C<csharp>
+=item C<erlang>
+
=item C<haskell>
=item C<java>
=back
+=head2 MAKING A STABLE RELEASE
+
+When we make a stable release, there are several steps documented
+here. See L</LIBGUESTFS VERSION NUMBERS> for general information
+about the stable branch policy.
+
+=over 4
+
+=item *
+
+Check C<make && make check> works on at least Fedora, Debian and
+Ubuntu.
+
+=item *
+
+Finalize RELEASE-NOTES.
+
+=item *
+
+Update ROADMAP.
+
+=item *
+
+Run C<src/api-support/update-from-tarballs.sh>.
+
+=item *
+
+Push and pull from Transifex.
+
+Run:
+
+ tx push -s
+
+to push the latest POT files to Transifex. Then run:
+
+ ./tx-pull.sh
+
+which is a wrapper to pull the latest translated C<*.po> files.
+
+=item *
+
+Create new stable and development directories under
+L<http://libguestfs.org/download>.
+
+=item *
+
+Create the branch in git:
+
+ git tag -a 1.XX.0 -m "Version 1.XX.0 (stable)"
+ git tag -a 1.YY.0 -m "Version 1.YY.0 (development)"
+ git branch stable-1.XX
+ git push origin tag 1.XX.0 1.YY.0 stable-1.XX
+
+=back
+
=head1 LIMITS
=head2 PROTOCOL LIMITS
=over 4
+=item FEBOOTSTRAP_KERNEL
+
+=item FEBOOTSTRAP_MODULES
+
+These two environment variables allow the kernel that libguestfs uses
+in the appliance to be selected. If C<$FEBOOTSTRAP_KERNEL> is not
+set, then the most recent host kernel is chosen. For more information
+about kernel selection, see L<febootstrap-supermin-helper(8)>. This
+feature is only available in febootstrap E<ge> 3.8.
+
=item LIBGUESTFS_APPEND
Pass additional options to the guest kernel.
=head1 SEE ALSO
L<guestfs-examples(3)>,
+L<guestfs-erlang(3)>,
+L<guestfs-java(3)>,
L<guestfs-ocaml(3)>,
+L<guestfs-perl(3)>,
L<guestfs-python(3)>,
L<guestfs-ruby(3)>,
L<guestfish(1)>,
L<virt-win-reg(1)>,
L<qemu(1)>,
L<febootstrap(1)>,
+L<febootstrap-supermin-helper(8)>,
L<hivex(3)>,
L<http://libguestfs.org/>.
git.annexia.org / libguestfs.git / blobdiff