New tool: virt-alignment-scan to check alignment of partitions.

[libguestfs.git] / src / guestfs.pod

diff --git a/src/guestfs.pod b/src/guestfs.pod
index 389bced..25ca56d 100644 (file)
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -42,8 +42,8 @@ FUSE.
 
 Libguestfs is a library that can be linked with C and C++ management
 programs (or management programs written in OCaml, Perl, Python, Ruby,
 
 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.
 
 You don't need to be root to use libguestfs, although obviously you do
 need enough permissions to access the disk images.


@@ -719,6 +719,10 @@ used.
 The C# bindings are highly experimental.  Please read the warnings
 at the top of C<csharp/Libguestfs.cs>.
 
 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<Haskell>
 
 This is the only language binding that is working but incomplete.


@@ -728,7 +732,7 @@ and we are looking for help to complete this binding.
 =item B<Java>
 
 Full documentation is contained in the Javadoc which is distributed
 =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 B<OCaml>
 


@@ -798,6 +802,9 @@ can make this very puzzling if you are trying to debug a problem.
 
 =item Mount option C<-o sync> should not be the default.
 
 
 =item Mount option C<-o sync> should not be the default.
 

+I<Update:> L</guestfs_mount> no longer adds any options starting
+from libguestfs 1.13.16.  This section only applies to older versions.
+

 If you use L</guestfs_mount>, then C<-o sync,noatime> are added
 implicitly.  However C<-o sync> does not add any reliability benefit,
 but does have a very large performance impact.
 If you use L</guestfs_mount>, then C<-o sync,noatime> are added
 implicitly.  However C<-o sync> does not add any reliability benefit,
 but does have a very large performance impact.


@@ -948,6 +955,29 @@ For example:
 Note that libguestfs also calls qemu with the -help and -version
 options in order to determine features.
 
 Note that libguestfs also calls qemu with the -help and -version
 options in order to determine features.
 

+Wrappers can also be used to edit the options passed to qemu.  In the
+following example, the C<-machine ...> option (C<-machine> and the
+following argument) are removed from the command line and replaced
+with C<-machine pc,accel=tcg>.  The while loop iterates over the
+options until it finds the right one to remove, putting the remaining
+options into the C<args> array.
+
+ #!/bin/bash -
+ 
+ i=0
+ while [ $# -gt 0 ]; do
+     case "$1" in
+     -machine)
+         shift 2;;
+     *)
+         args[i]="$1"
+         (( i++ ))
+         shift ;;
+     esac
+ done
+ 
+ exec qemu-kvm -machine pc,accel=tcg "${args[@]}"
+

 =head2 ATTACHING TO RUNNING DAEMONS
 
 I<Note (1):> This is B<highly experimental> and has a tendency to eat
 =head2 ATTACHING TO RUNNING DAEMONS
 
 I<Note (1):> This is B<highly experimental> and has a tendency to eat


@@ -1285,7 +1315,7 @@ Create a handle by calling L</guestfs_create>.  Call L</guestfs_close>
 to free the handle and release all resources used.
 
 For information on using multiple handles and threads, see the section
 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
 
 
 =head2 guestfs_create
 


@@ -1344,8 +1374,6 @@ been printed to C<stderr> before the program exits.
 For other programs the caller will almost certainly want to install an
 alternate error handler or do error handling in-line like this:
 
 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);
  /* This disables the default behaviour of printing errors
     on stderr. */
  guestfs_set_error_handler (g, NULL, NULL);


@@ -1354,9 +1382,12 @@ alternate error handler or do error handling in-line like this:
    /* Examine the error message and print it etc. */
    char *msg = guestfs_last_error (g);
    int errnum = guestfs_last_errno (g);
    /* 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
 
 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


@@ -1452,8 +1483,8 @@ Returns the current error handler callback.
 =head2 guestfs_set_out_of_memory_handler
 
  typedef void (*guestfs_abort_cb) (void);
 =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>.
 
 The callback C<cb> will be called if there is an out of memory
 situation.  I<Note this callback must not return>.


@@ -1672,7 +1703,8 @@ old functions C<guestfs_set_log_message_callback>,
 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
 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
 
 Handles generate events when certain things happen, such as log
 messages being generated, progress messages during long-running


@@ -1831,6 +1863,21 @@ If no callback is registered: the messages are sent to stderr.  You
 can override the printing of trace messages to stderr by setting up a
 callback.
 
 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
 =back
 
 =head3 guestfs_set_event_callback


@@ -1948,6 +1995,45 @@ this example, messages are directed to syslog:
      syslog (priority, "event 0x%lx: %s", event, buf);
  }
 
      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 PRIVATE DATA AREA
 
 You can attach named pieces of private data to the libguestfs handle,


@@ -1961,12 +2047,13 @@ To attach a named piece of data, use the following call:
 
 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
 
 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:
 
 
 To retrieve the pointer, use:
 


@@ -2186,6 +2273,99 @@ callback to receive these messages.
 
 =head1 INTERNALS
 
 
 =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
 =head2 COMMUNICATION PROTOCOL
 
 Don't rely on using this protocol directly.  This section documents


@@ -2643,6 +2823,10 @@ the programmers.
 
 =over 4
 
 
 =over 4
 

+=item C<align>
+
+L<virt-alignment-scan(1)> command and documentation.
+

 =item C<appliance>
 
 The libguestfs appliance, build scripts and so on.
 =item C<appliance>
 
 The libguestfs appliance, build scripts and so on.


@@ -2656,6 +2840,11 @@ Automated tests of the C API.
 The L<virt-cat(1)>, L<virt-filesystems(1)> and L<virt-ls(1)> commands
 and documentation.
 
 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.
 =item C<contrib>
 
 Outside contributions, experimental parts.


@@ -2669,6 +2858,10 @@ actions.
 
 L<virt-df(1)> command and documentation.
 
 
 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<examples>
 
 C API example code.


@@ -2724,13 +2917,21 @@ Regression tests.
 
 L<virt-rescue(1)> command and documentation.
 
 
 L<virt-rescue(1)> command and documentation.
 

+=item C<resize>
+
+L<virt-resize(1)> command and documentation.
+
+=item C<sparsify>
+
+L<virt-sparsify(1)> command and documentation.
+

 =item C<src>
 
 Source code to the C library.
 
 =item C<tools>
 
 =item C<src>
 
 Source code to the C library.
 
 =item C<tools>
 

-Command line tools written in Perl (L<virt-resize(1)> and many others).
+Command line tools written in Perl (L<virt-win-reg(1)> and many others).

 
 =item C<test-tool>
 
 
 =item C<test-tool>
 


@@ -2739,6 +2940,8 @@ will work with libguestfs.
 
 =item C<csharp>
 
 
 =item C<csharp>
 

+=item C<erlang>
+

 =item C<haskell>
 
 =item C<java>
 =item C<haskell>
 
 =item C<java>


@@ -2757,6 +2960,61 @@ Language bindings.
 
 =back
 
 
 =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
 =head1 LIMITS
 
 =head2 PROTOCOL LIMITS


@@ -2817,6 +3075,15 @@ We have tested block devices up to 1 exabyte (2**60 or
 1,152,921,504,606,846,976 bytes) using sparse files backed by an XFS
 host filesystem.
 
 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
 =head2 MAXIMUM SIZE OF A PARTITION
 
 The MBR (ie. classic MS-DOS) partitioning scheme uses 32 bit sector


@@ -2852,6 +3119,16 @@ be reached in practice.  See the source code for more information.
 
 =over 4
 
 
 =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.
 =item LIBGUESTFS_APPEND
 
 Pass additional options to the guest kernel.


@@ -2902,11 +3179,15 @@ enough.
 =head1 SEE ALSO
 
 L<guestfs-examples(3)>,
 =head1 SEE ALSO
 
 L<guestfs-examples(3)>,

+L<guestfs-erlang(3)>,
+L<guestfs-java(3)>,

 L<guestfs-ocaml(3)>,
 L<guestfs-ocaml(3)>,

+L<guestfs-perl(3)>,

 L<guestfs-python(3)>,
 L<guestfs-ruby(3)>,
 L<guestfish(1)>,
 L<guestmount(1)>,
 L<guestfs-python(3)>,
 L<guestfs-ruby(3)>,
 L<guestfish(1)>,
 L<guestmount(1)>,

+L<virt-alignment-scan(1)>,

 L<virt-cat(1)>,
 L<virt-copy-in(1)>,
 L<virt-copy-out(1)>,
 L<virt-cat(1)>,
 L<virt-copy-in(1)>,
 L<virt-copy-out(1)>,


@@ -2919,12 +3200,15 @@ L<virt-list-partitions(1)>,
 L<virt-ls(1)>,
 L<virt-make-fs(1)>,
 L<virt-rescue(1)>,
 L<virt-ls(1)>,
 L<virt-make-fs(1)>,
 L<virt-rescue(1)>,

+L<virt-resize(1)>,
+L<virt-sparsify(1)>,

 L<virt-tar(1)>,
 L<virt-tar-in(1)>,
 L<virt-tar-out(1)>,
 L<virt-win-reg(1)>,
 L<qemu(1)>,
 L<febootstrap(1)>,
 L<virt-tar(1)>,
 L<virt-tar-in(1)>,
 L<virt-tar-out(1)>,
 L<virt-win-reg(1)>,
 L<qemu(1)>,
 L<febootstrap(1)>,

+L<febootstrap-supermin-helper(8)>,

 L<hivex(3)>,
 L<http://libguestfs.org/>.
 
 L<hivex(3)>,
 L<http://libguestfs.org/>.