guestfs_download (g, filename, "/dev/stdout");
-and you can write tar output to a pipe C<fd> by doing:
+and you can write tar output to a file descriptor C<fd> by doing:
char devfd[64];
snprintf (devfd, sizeof devfd, "/dev/fd/%d", fd);
=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>
=item Autosync / forgetting to sync.
+I<Update:> Autosync is enabled by default for all API users starting
+from libguestfs 1.5.24. This section only applies to older versions.
+
When modifying a filesystem from C or another language, you B<must>
unmount all filesystems and call L</guestfs_sync> explicitly before
you close the libguestfs handle. You can also call:
dirty guestfish scripts that forget to sync will work just fine, which
can make this very puzzling if you are trying to debug a problem.
-Update: Autosync is enabled by default for all API users starting from
-libguestfs 1.5.24.
-
=item Mount option C<-o sync> should not be the default.
If you use L</guestfs_mount>, then C<-o sync,noatime> are added
to free the handle and release all resources used.
For information on using multiple handles and threads, see the section
-L</MULTIPLE HANDLES AND MULTIPLE THREADS> below.
+L</MULTIPLE HANDLES AND MULTIPLE THREADS> above.
=head2 guestfs_create
Create a connection handle.
-You have to call L</guestfs_add_drive_opts> (or one of the equivalent
-calls) on the handle at least once.
+On success this returns a non-NULL pointer to a handle. On error it
+returns NULL.
-This function returns a non-NULL pointer to a handle on success or
-NULL on error.
+You have to "configure" the handle after creating it. This includes
+calling L</guestfs_add_drive_opts> (or one of the equivalent calls) on
+the handle at least once.
After configuring the handle, you have to call L</guestfs_launch>.
-You may also want to configure error handling for the handle. See
+You may also want to configure error handling for the handle. See the
L</ERROR HANDLING> section below.
=head2 guestfs_close
This closes the connection handle and frees up all resources used.
+If autosync was set on the handle and the handle was launched, then
+this implicitly calls various functions to unmount filesystems and
+sync the disk. See L</guestfs_set_autosync> for more details.
+
+If a close callback was set on the handle, then it is called.
+
=head1 ERROR HANDLING
API functions can return errors. For example, almost all functions
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>.
C<guestfs_set_subprocess_quit_callback>,
C<guestfs_set_launch_done_callback>, C<guestfs_set_close_callback> and
C<guestfs_set_progress_callback> are no longer documented in this
-manual page.
+manual page. Because of the ABI guarantee, the old functions continue
+to work.
Handles generate events when certain things happen, such as log
messages being generated, progress messages during long-running
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,
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.
+same key 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.
+You can use any C<key> you want, but your key should I<not> start with
+an underscore character. Keys beginning with an underscore character
+are reserved for internal libguestfs purposes (eg. for implementing
+language bindings). It is recommended that you prefix the key with
+some unique string to avoid collisions with other users.
To retrieve the pointer, use:
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.
=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
1,152,921,504,606,846,976 bytes) using sparse files backed by an XFS
host filesystem.
+Although libguestfs probably does not impose any limit, the underlying
+host storage will. If you store disk images on a host ext4
+filesystem, then the maximum size will be limited by the maximum ext4
+file size (currently 16 TB). If you store disk images as host logical
+volumes then you are limited by the maximum size of an LV.
+
+For the hugest disk image files, we recommend using XFS on the host
+for storage.
+
=head2 MAXIMUM SIZE OF A PARTITION
The MBR (ie. classic MS-DOS) partitioning scheme uses 32 bit sector
=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-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/>.