X-Git-Url: http://git.annexia.org/?p=libguestfs.git;a=blobdiff_plain;f=guestfs.pod;h=d8e4da3b3925d799fa4986a357f9ee7590cfac2b;hp=c7310a649da61a9851f681e3eb8e6b7388861431;hb=5da810b96072c0fd71d78713025a2e104295d0ff;hpb=a7b73d4a1e09f12b2002083618056f0c823c1dcf

diff --git a/guestfs.pod b/guestfs.pod
index c7310a6..d8e4da3 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -78,7 +78,7 @@ 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.
+section L</ERROR HANDLING> below for how to handle errors.
 
 =head2 guestfs_h *
 
@@ -87,7 +87,7 @@ Create a handle by calling C<guestfs_create>.  Call C<guestfs_close>
 to free the handle and release all resources used.
 
 For information on using multiple handles and threads, see the section
-MULTIPLE HANDLES AND MULTIPLE THREADS below.
+L</MULTIPLE HANDLES AND MULTIPLE THREADS> below.
 
 =head2 guestfs_create
 
@@ -104,7 +104,7 @@ 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.
+L</ERROR HANDLING> section below.
 
 =head2 guestfs_close
 
@@ -203,6 +203,186 @@ 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).
+
+=item *
+
+For SELinux guests, you may need to enable SELinux and load policy
+first.  See L</SELINUX> in this manpage.
+
+=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.
+
+=head2 SELINUX
+
+We support SELinux guests.  To ensure that labeling happens correctly
+in SELinux guests, you need to enable SELinux and load the guest's
+policy:
+
+=over 4
+
+=item 1.
+
+Before launching, do:
+
+ guestfs_set_selinux (g, 1);
+
+=item 2.
+
+After mounting the guest's filesystem(s), load the policy.  This
+is best done by running the L<load_policy(8)> command in the
+guest itself:
+
+ guestfs_sh (g, "/usr/sbin/load_policy");
+
+(Older versions of C<load_policy> require you to specify the
+name of the policy file).
+
+=item 3.
+
+Optionally, set the security context for the API.  The correct
+security context to use can only be known by inspecting the
+guest.  As an example:
+
+ guestfs_setcon (g, "unconfined_u:unconfined_r:unconfined_t:s0");
+
+=back
+
+This will work for running commands and editing existing files.
+
+When new files are created, you may need to label them explicitly,
+for example by running the external command
+C<restorecon pathname>.
+
 =head1 HIGH-LEVEL API ACTIONS
 
 =head2 ABI GUARANTEE
@@ -801,7 +981,17 @@ Set the default qemu binary that libguestfs uses.  If not set, then
 the qemu which was found at compile time by the configure script is
 used.
 
-See also L<QEMU WRAPPERS> above.
+See also L</QEMU WRAPPERS> above.
+
+=item TMPDIR
+
+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
 
@@ -812,6 +1002,13 @@ 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:
@@ -838,6 +1035,11 @@ 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