X-Git-Url: http://git.annexia.org/?p=libguestfs.git;a=blobdiff_plain;f=guestfs.pod;h=4d462f34c599d77c4c0d9fc474a311485e2ea977;hp=3dad35c40d990acafc37c3d1042d3930e13f7b77;hb=58e7e42033b1ac5044ae03f0aa5d5082c5fdb497;hpb=d3270cfadd3416bd9961a2c6fb1cc131c43979da

diff --git a/guestfs.pod b/guestfs.pod
index 3dad35c..4d462f3 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -7,7 +7,7 @@ guestfs - Library for accessing and modifying virtual machine images
 =head1 SYNOPSIS
 
  #include <guestfs.h>
- 
+
  guestfs_h *handle = guestfs_create ();
  guestfs_add_drive (handle, "guest.img");
  guestfs_launch (handle);
@@ -49,28 +49,28 @@ 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);
 
 C<guestfs_wait_ready> and all of the actions including C<guestfs_sync>
@@ -168,7 +168,7 @@ If you set C<cb> to C<NULL> then I<no> handler is called.
 
 Returns the current error handler callback.
 
-=head2 guestfs_set_out_of_memory_handler 
+=head2 guestfs_set_out_of_memory_handler
 
  typedef void (*guestfs_abort_cb) (void);
  int guestfs_set_out_of_memory_handler (guestfs_h *handle,
@@ -203,6 +203,140 @@ 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 API OVERVIEW
+
+This section provides additional documentation for groups of API
+calls, which may not be obvious from reading about the individual
+calls below.
+
+=head2 LVM2
+
+Libguestfs provides access to a large part of the LVM2 API.  It won't
+make much sense unless you familiarize yourself with the concepts of
+physical volumes, volume groups and logical volumes.
+
+This author strongly recommends reading the LVM HOWTO, online at
+L<http://tldp.org/HOWTO/LVM-HOWTO/>.
+
+=head2 PARTITIONING
+
+To create MBR-style (ie. normal PC) partitions use one of the
+C<guestfs_sfdisk*> variants.  These calls use the external
+L<sfdisk(8)> command.
+
+The simplest call is:
+
+ char *lines[] = { ",", NULL };
+ guestfs_sfdiskM (g, "/dev/sda", lines);
+
+This will create a single partition on C</dev/sda> called
+C</dev/sda1> covering the whole disk.
+
+In general MBR partitions are both unnecessarily complicated and
+depend on archaic details, namely the Cylinder-Head-Sector (CHS)
+geometry of the disk.  C<guestfs_sfdiskM> allows you to specify sizes
+in megabytes instead of cylinders, which is a small win.
+C<guestfs_sfdiskM> will choose the nearest cylinder to approximate the
+requested size.  There's a lot of crazy stuff to do with IDE and
+virtio disks having different, incompatible CHS geometries, that you
+probably don't want to know about.  My advice: make a single partition
+to cover the whole disk, then use LVM on top.
+
+In future we aim to provide access to libparted.
+
+=head2 UPLOADING
+
+For small, single files, use C<guestfs_write_file>.  In some versions
+of libguestfs there was a bug which limited this call to text files
+(not containing ASCII NUL characters).
+
+To upload a single file, use C<guestfs_upload>.  This call has no
+limits on file content or size (even files larger than 4 GB).
+
+To upload multiple files, see C<guestfs_tar_in> and C<guestfs_tgz_in>.
+
+However the fastest way to upload I<large numbers of arbitrary files>
+is to turn them into a squashfs or CD ISO (see L<mksquashfs(8)> and
+L<mkisofs(8)>), then attach this using C<guestfs_add_drive_ro>.  If
+you add the drive in a predictable way (eg. adding it last after all
+other drives) then you can get the device name from
+C<guestfs_list_devices> and mount it directly using
+C<guestfs_mount_ro>.  Note that squashfs images are sometimes
+non-portable between kernel versions, and they don't support labels or
+UUIDs.  If you want to pre-build an image or you need to mount it
+using a label or UUID, use an ISO image instead.
+
+=head2 DOWNLOADING
+
+Use C<guestfs_cat> to download small, text only files.  This call
+is limited to files which are less than 2 MB and which cannot contain
+any ASCII NUL (C<\0>) characters.  However it has a very simple
+to use API.
+
+C<guestfs_read_file> can be used to read files which contain
+arbitrary 8 bit data, since it returns a (pointer, size) pair.
+However it is still limited to "small" files, less than 2 MB.
+
+C<guestfs_download> can be used to download any file, with no
+limits on content or size (even files larger than 4 GB).
+
+To download multiple files, see C<guestfs_tar_out> and
+C<guestfs_tgz_out>.
+
+=head2 RUNNING COMMANDS
+
+Although libguestfs is a primarily an API for manipulating files
+inside guest images, we also provide some limited facilities for
+running commands inside guests.
+
+There are many limitations to this:
+
+=over 4
+
+=item *
+
+The kernel version that the command runs under will be different
+from what it expects.
+
+=item *
+
+If the command needs to communicate with daemons, then most likely
+they won't be running.
+
+=item *
+
+The command will be running in limited memory.
+
+=item *
+
+Only supports Linux guests (not Windows, BSD, etc).
+
+=item *
+
+Architecture limitations (eg. won't work for a PPC guest on
+an X86 host).
+
+=back
+
+The two main API calls to run commands are C<guestfs_command> and
+C<guestfs_sh> (there are also variations).
+
+The difference is that C<guestfs_sh> runs commands using the shell, so
+any shell globs, redirections, etc will work.
+
+=head2 LISTING FILES
+
+C<guestfs_ll> is just designed for humans to read (mainly when using
+the L<guestfish(1)>-equivalent command C<ll>).
+
+C<guestfs_ls> is a quick way to get a list of files in a directory
+from programs.
+
+C<guestfs_readdir> is a programmatic way to get a list of files in a
+directory, plus additional information about each one.
+
+C<guestfs_find> can be used to recursively list files.
+
 =head1 HIGH-LEVEL API ACTIONS
 
 =head2 ABI GUARANTEE
@@ -774,11 +908,22 @@ options in order to determine features.
 
 =over 4
 
+=item LIBGUESTFS_APPEND
+
+Pass additional options to the guest kernel.
+
 =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_MEMSIZE
+
+Set the memory allocated to the qemu process, in megabytes.  For
+example:
+
+ LIBGUESTFS_MEMSIZE=700
+
 =item LIBGUESTFS_PATH
 
 Set the path that libguestfs uses to search for kernel and initrd.img.
@@ -792,9 +937,15 @@ used.
 
 See also L<QEMU WRAPPERS> above.
 
-=item LIBGUESTFS_APPEND
+=item TMPDIR
 
-Pass additional options to the guest kernel.
+Location of temporary directory, defaults to C</tmp>.
+
+If libguestfs was compiled to use the supermin appliance then each
+handle will require rather a large amount of space in this directory
+for short periods of time (~ 80 MB).  You can use C<$TMPDIR> to
+configure another directory to use in case C</tmp> is not large
+enough.
 
 =back
 
@@ -805,6 +956,13 @@ L<qemu(1)>,
 L<febootstrap(1)>,
 L<http://libguestfs.org/>.
 
+Tools with a similar purpose:
+L<fdisk(8)>,
+L<parted(8)>,
+L<kpartx(8)>,
+L<lvm(8)>,
+L<disktype(1)>.
+
 =head1 BUGS
 
 To get a list of bugs against libguestfs use this link:
@@ -831,6 +989,11 @@ That you are testing a recent version.
 
 Describe the bug accurately, and give a way to reproduce it.
 
+=item *
+
+Run libguestfs-test-tool and paste the B<complete, unedited>
+output into the bug report.
+
 =back
 
 =head1 AUTHORS