fish: handle some out-of-memory conditions

[libguestfs.git] / guestfs-actions.pod

=head2 guestfs_add_cdrom

 int guestfs_add_cdrom (guestfs_h *handle,
                const char *filename);

This function adds a virtual CD-ROM disk image to the guest.

This is equivalent to the qemu parameter C<-cdrom filename>.

Note that this call checks for the existence of C<filename>.  This
stops you from specifying other types of drive which are supported
by qemu such as C<nbd:> and C<http:> URLs.  To specify those, use
the general C<guestfs_config> call instead.

This function returns 0 on success or -1 on error.

=head2 guestfs_add_drive

 int guestfs_add_drive (guestfs_h *handle,
                const char *filename);

This function adds a virtual machine disk image C<filename> to the
guest.  The first time you call this function, the disk appears as IDE
disk 0 (C</dev/sda>) in the guest, the second time as C</dev/sdb>, and
so on.

You don't necessarily need to be root when using libguestfs.  However
you obviously do need sufficient permissions to access the filename
for whatever operations you want to perform (ie. read access if you
just want to read the image or write access if you want to modify the
image).

This is equivalent to the qemu parameter
C<-drive file=filename,cache=off,if=virtio>.

Note that this call checks for the existence of C<filename>.  This
stops you from specifying other types of drive which are supported
by qemu such as C<nbd:> and C<http:> URLs.  To specify those, use
the general C<guestfs_config> call instead.

This function returns 0 on success or -1 on error.

=head2 guestfs_add_drive_ro

 int guestfs_add_drive_ro (guestfs_h *handle,
                const char *filename);

This adds a drive in snapshot mode, making it effectively
read-only.

Note that writes to the device are allowed, and will be seen for
the duration of the guestfs handle, but they are written
to a temporary file which is discarded as soon as the guestfs
handle is closed.  We don't currently have any method to enable
changes to be committed, although qemu can support this.

This is equivalent to the qemu parameter
C<-drive file=filename,snapshot=on,if=virtio>.

Note that this call checks for the existence of C<filename>.  This
stops you from specifying other types of drive which are supported
by qemu such as C<nbd:> and C<http:> URLs.  To specify those, use
the general C<guestfs_config> call instead.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_close

 int guestfs_aug_close (guestfs_h *handle);

Close the current Augeas handle and free up any resources
used by it.  After calling this, you have to call
C<guestfs_aug_init> again before you can use any other
Augeas functions.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_defnode

 struct guestfs_int_bool *guestfs_aug_defnode (guestfs_h *handle,
                const char *name,
                const char *expr,
                const char *val);

Defines a variable C<name> whose value is the result of
evaluating C<expr>.

If C<expr> evaluates to an empty nodeset, a node is created,
equivalent to calling C<guestfs_aug_set> C<expr>, C<value>.
C<name> will be the nodeset containing that single node.

On success this returns a pair containing the
number of nodes in the nodeset, and a boolean flag
if a node was created.

This function returns a C<struct guestfs_int_bool *>,
or NULL if there was an error.
I<The caller must call C<guestfs_free_int_bool> after use>.

=head2 guestfs_aug_defvar

 int guestfs_aug_defvar (guestfs_h *handle,
                const char *name,
                const char *expr);

Defines an Augeas variable C<name> whose value is the result
of evaluating C<expr>.  If C<expr> is NULL, then C<name> is
undefined.

On success this returns the number of nodes in C<expr>, or
C<0> if C<expr> evaluates to something which is not a nodeset.

On error this function returns -1.

=head2 guestfs_aug_get

 char *guestfs_aug_get (guestfs_h *handle,
                const char *path);

Look up the value associated with C<path>.  If C<path>
matches exactly one node, the C<value> is returned.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_aug_init

 int guestfs_aug_init (guestfs_h *handle,
                const char *root,
                int flags);

Create a new Augeas handle for editing configuration files.
If there was any previous Augeas handle associated with this
guestfs session, then it is closed.

You must call this before using any other C<guestfs_aug_*>
commands.

C<root> is the filesystem root.  C<root> must not be NULL,
use C</> instead.

The flags are the same as the flags defined in
E<lt>augeas.hE<gt>, the logical I<or> of the following
integers:

=over 4

=item C<AUG_SAVE_BACKUP> = 1

Keep the original file with a C<.augsave> extension.

=item C<AUG_SAVE_NEWFILE> = 2

Save changes into a file with extension C<.augnew>, and
do not overwrite original.  Overrides C<AUG_SAVE_BACKUP>.

=item C<AUG_TYPE_CHECK> = 4

Typecheck lenses (can be expensive).

=item C<AUG_NO_STDINC> = 8

Do not use standard load path for modules.

=item C<AUG_SAVE_NOOP> = 16

Make save a no-op, just record what would have been changed.

=item C<AUG_NO_LOAD> = 32

Do not load the tree in C<guestfs_aug_init>.

=back

To close the handle, you can call C<guestfs_aug_close>.

To find out more about Augeas, see L<http://augeas.net/>.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_insert

 int guestfs_aug_insert (guestfs_h *handle,
                const char *path,
                const char *label,
                int before);

Create a new sibling C<label> for C<path>, inserting it into
the tree before or after C<path> (depending on the boolean
flag C<before>).

C<path> must match exactly one existing node in the tree, and
C<label> must be a label, ie. not contain C</>, C<*> or end
with a bracketed index C<[N]>.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_load

 int guestfs_aug_load (guestfs_h *handle);

Load files into the tree.

See C<aug_load> in the Augeas documentation for the full gory
details.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_ls

 char **guestfs_aug_ls (guestfs_h *handle,
                const char *path);

This is just a shortcut for listing C<guestfs_aug_match>
C<path/*> and sorting the resulting nodes into alphabetical order.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_aug_match

 char **guestfs_aug_match (guestfs_h *handle,
                const char *path);

Returns a list of paths which match the path expression C<path>.
The returned paths are sufficiently qualified so that they match
exactly one node in the current tree.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_aug_mv

 int guestfs_aug_mv (guestfs_h *handle,
                const char *src,
                const char *dest);

Move the node C<src> to C<dest>.  C<src> must match exactly
one node.  C<dest> is overwritten if it exists.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_rm

 int guestfs_aug_rm (guestfs_h *handle,
                const char *path);

Remove C<path> and all of its children.

On success this returns the number of entries which were removed.

On error this function returns -1.

=head2 guestfs_aug_save

 int guestfs_aug_save (guestfs_h *handle);

This writes all pending changes to disk.

The flags which were passed to C<guestfs_aug_init> affect exactly
how files are saved.

This function returns 0 on success or -1 on error.

=head2 guestfs_aug_set

 int guestfs_aug_set (guestfs_h *handle,
                const char *path,
                const char *val);

Set the value associated with C<path> to C<value>.

This function returns 0 on success or -1 on error.

=head2 guestfs_blockdev_flushbufs

 int guestfs_blockdev_flushbufs (guestfs_h *handle,
                const char *device);

This tells the kernel to flush internal buffers associated
with C<device>.

This uses the L<blockdev(8)> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_blockdev_getbsz

 int guestfs_blockdev_getbsz (guestfs_h *handle,
                const char *device);

This returns the block size of a device.

(Note this is different from both I<size in blocks> and
I<filesystem block size>).

This uses the L<blockdev(8)> command.

On error this function returns -1.

=head2 guestfs_blockdev_getro

 int guestfs_blockdev_getro (guestfs_h *handle,
                const char *device);

Returns a boolean indicating if the block device is read-only
(true if read-only, false if not).

This uses the L<blockdev(8)> command.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_blockdev_getsize64

 int64_t guestfs_blockdev_getsize64 (guestfs_h *handle,
                const char *device);

This returns the size of the device in bytes.

See also C<guestfs_blockdev_getsz>.

This uses the L<blockdev(8)> command.

On error this function returns -1.

=head2 guestfs_blockdev_getss

 int guestfs_blockdev_getss (guestfs_h *handle,
                const char *device);

This returns the size of sectors on a block device.
Usually 512, but can be larger for modern devices.

(Note, this is not the size in sectors, use C<guestfs_blockdev_getsz>
for that).

This uses the L<blockdev(8)> command.

On error this function returns -1.

=head2 guestfs_blockdev_getsz

 int64_t guestfs_blockdev_getsz (guestfs_h *handle,
                const char *device);

This returns the size of the device in units of 512-byte sectors
(even if the sectorsize isn't 512 bytes ... weird).

See also C<guestfs_blockdev_getss> for the real sector size of
the device, and C<guestfs_blockdev_getsize64> for the more
useful I<size in bytes>.

This uses the L<blockdev(8)> command.

On error this function returns -1.

=head2 guestfs_blockdev_rereadpt

 int guestfs_blockdev_rereadpt (guestfs_h *handle,
                const char *device);

Reread the partition table on C<device>.

This uses the L<blockdev(8)> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_blockdev_setbsz

 int guestfs_blockdev_setbsz (guestfs_h *handle,
                const char *device,
                int blocksize);

This sets the block size of a device.

(Note this is different from both I<size in blocks> and
I<filesystem block size>).

This uses the L<blockdev(8)> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_blockdev_setro

 int guestfs_blockdev_setro (guestfs_h *handle,
                const char *device);

Sets the block device named C<device> to read-only.

This uses the L<blockdev(8)> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_blockdev_setrw

 int guestfs_blockdev_setrw (guestfs_h *handle,
                const char *device);

Sets the block device named C<device> to read-write.

This uses the L<blockdev(8)> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_cat

 char *guestfs_cat (guestfs_h *handle,
                const char *path);

Return the contents of the file named C<path>.

Note that this function cannot correctly handle binary files
(specifically, files containing C<\0> character which is treated
as end of string).  For those you need to use the C<guestfs_download>
function which has a more complex interface.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_checksum

 char *guestfs_checksum (guestfs_h *handle,
                const char *csumtype,
                const char *path);

This call computes the MD5, SHAx or CRC checksum of the
file named C<path>.

The type of checksum to compute is given by the C<csumtype>
parameter which must have one of the following values:

=over 4

=item C<crc>

Compute the cyclic redundancy check (CRC) specified by POSIX
for the C<cksum> command.

=item C<md5>

Compute the MD5 hash (using the C<md5sum> program).

=item C<sha1>

Compute the SHA1 hash (using the C<sha1sum> program).

=item C<sha224>

Compute the SHA224 hash (using the C<sha224sum> program).

=item C<sha256>

Compute the SHA256 hash (using the C<sha256sum> program).

=item C<sha384>

Compute the SHA384 hash (using the C<sha384sum> program).

=item C<sha512>

Compute the SHA512 hash (using the C<sha512sum> program).

=back

The checksum is returned as a printable string.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_chmod

 int guestfs_chmod (guestfs_h *handle,
                int mode,
                const char *path);

Change the mode (permissions) of C<path> to C<mode>.  Only
numeric modes are supported.

This function returns 0 on success or -1 on error.

=head2 guestfs_chown

 int guestfs_chown (guestfs_h *handle,
                int owner,
                int group,
                const char *path);

Change the file owner to C<owner> and group to C<group>.

Only numeric uid and gid are supported.  If you want to use
names, you will need to locate and parse the password file
yourself (Augeas support makes this relatively easy).

This function returns 0 on success or -1 on error.

=head2 guestfs_command

 char *guestfs_command (guestfs_h *handle,
                char * const* const arguments);

This call runs a command from the guest filesystem.  The
filesystem must be mounted, and must contain a compatible
operating system (ie. something Linux, with the same
or compatible processor architecture).

The single parameter is an argv-style list of arguments.
The first element is the name of the program to run.
Subsequent elements are parameters.  The list must be
non-empty (ie. must contain a program name).  Note that
the command runs directly, and is I<not> invoked via
the shell (see C<guestfs_sh>).

The return value is anything printed to I<stdout> by
the command.

If the command returns a non-zero exit status, then
this function returns an error message.  The error message
string is the content of I<stderr> from the command.

The C<$PATH> environment variable will contain at least
C</usr/bin> and C</bin>.  If you require a program from
another location, you should provide the full path in the
first parameter.

Shared libraries and data files required by the program
must be available on filesystems which are mounted in the
correct places.  It is the caller's responsibility to ensure
all filesystems that are needed are mounted at the right
locations.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_command_lines

 char **guestfs_command_lines (guestfs_h *handle,
                char * const* const arguments);

This is the same as C<guestfs_command>, but splits the
result into a list of lines.

See also: C<guestfs_sh_lines>

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_config

 int guestfs_config (guestfs_h *handle,
                const char *qemuparam,
                const char *qemuvalue);

This can be used to add arbitrary qemu command line parameters
of the form C<-param value>.  Actually it's not quite arbitrary - we
prevent you from setting some parameters which would interfere with
parameters that we use.

The first character of C<param> string must be a C<-> (dash).

C<value> can be NULL.

This function returns 0 on success or -1 on error.

=head2 guestfs_cp

 int guestfs_cp (guestfs_h *handle,
                const char *src,
                const char *dest);

This copies a file from C<src> to C<dest> where C<dest> is
either a destination filename or destination directory.

This function returns 0 on success or -1 on error.

=head2 guestfs_cp_a

 int guestfs_cp_a (guestfs_h *handle,
                const char *src,
                const char *dest);

This copies a file or directory from C<src> to C<dest>
recursively using the C<cp -a> command.

This function returns 0 on success or -1 on error.

=head2 guestfs_debug

 char *guestfs_debug (guestfs_h *handle,
                const char *subcmd,
                char * const* const extraargs);

The C<guestfs_debug> command exposes some internals of
C<guestfsd> (the guestfs daemon) that runs inside the
qemu subprocess.

There is no comprehensive help for this command.  You have
to look at the file C<daemon/debug.c> in the libguestfs source
to find out what you can do.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_df

 char *guestfs_df (guestfs_h *handle);

This command runs the C<df> command to report disk space used.

This command is mostly useful for interactive sessions.  It
is I<not> intended that you try to parse the output string.
Use C<statvfs> from programs.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_df_h

 char *guestfs_df_h (guestfs_h *handle);

This command runs the C<df -h> command to report disk space used
in human-readable format.

This command is mostly useful for interactive sessions.  It
is I<not> intended that you try to parse the output string.
Use C<statvfs> from programs.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_dmesg

 char *guestfs_dmesg (guestfs_h *handle);

This returns the kernel messages (C<dmesg> output) from
the guest kernel.  This is sometimes useful for extended
debugging of problems.

Another way to get the same information is to enable
verbose messages with C<guestfs_set_verbose> or by setting
the environment variable C<LIBGUESTFS_DEBUG=1> before
running the program.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_download

 int guestfs_download (guestfs_h *handle,
                const char *remotefilename,
                const char *filename);

Download file C<remotefilename> and save it as C<filename>
on the local machine.

C<filename> can also be a named pipe.

See also C<guestfs_upload>, C<guestfs_cat>.

This function returns 0 on success or -1 on error.

=head2 guestfs_drop_caches

 int guestfs_drop_caches (guestfs_h *handle,
                int whattodrop);

This instructs the guest kernel to drop its page cache,
and/or dentries and inode caches.  The parameter C<whattodrop>
tells the kernel what precisely to drop, see
L<http://linux-mm.org/Drop_Caches>

Setting C<whattodrop> to 3 should drop everything.

This automatically calls L<sync(2)> before the operation,
so that the maximum guest memory is freed.

This function returns 0 on success or -1 on error.

=head2 guestfs_du

 int64_t guestfs_du (guestfs_h *handle,
                const char *path);

This command runs the C<du -s> command to estimate file space
usage for C<path>.

C<path> can be a file or a directory.  If C<path> is a directory
then the estimate includes the contents of the directory and all
subdirectories (recursively).

The result is the estimated size in I<kilobytes>
(ie. units of 1024 bytes).

On error this function returns -1.

=head2 guestfs_e2fsck_f

 int guestfs_e2fsck_f (guestfs_h *handle,
                const char *device);

This runs C<e2fsck -p -f device>, ie. runs the ext2/ext3
filesystem checker on C<device>, noninteractively (C<-p>),
even if the filesystem appears to be clean (C<-f>).

This command is only needed because of C<guestfs_resize2fs>
(q.v.).  Normally you should use C<guestfs_fsck>.

This function returns 0 on success or -1 on error.

=head2 guestfs_end_busy

 int guestfs_end_busy (guestfs_h *handle);

This sets the state to C<READY>, or if in C<CONFIG> then it leaves the
state as is.  This is only used when implementing
actions using the low-level API.

For more information on states, see L<guestfs(3)>.

This function returns 0 on success or -1 on error.

=head2 guestfs_equal

 int guestfs_equal (guestfs_h *handle,
                const char *file1,
                const char *file2);

This compares the two files C<file1> and C<file2> and returns
true if their content is exactly equal, or false otherwise.

The external L<cmp(1)> program is used for the comparison.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_exists

 int guestfs_exists (guestfs_h *handle,
                const char *path);

This returns C<true> if and only if there is a file, directory
(or anything) with the given C<path> name.

See also C<guestfs_is_file>, C<guestfs_is_dir>, C<guestfs_stat>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_file

 char *guestfs_file (guestfs_h *handle,
                const char *path);

This call uses the standard L<file(1)> command to determine
the type or contents of the file.  This also works on devices,
for example to find out whether a partition contains a filesystem.

The exact command which runs is C<file -bsL path>.  Note in
particular that the filename is not prepended to the output
(the C<-b> option).

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_find

 char **guestfs_find (guestfs_h *handle,
                const char *directory);

This command lists out all files and directories, recursively,
starting at C<directory>.  It is essentially equivalent to
running the shell command C<find directory -print> but some
post-processing happens on the output, described below.

This returns a list of strings I<without any prefix>.  Thus
if the directory structure was:

 /tmp/a
 /tmp/b
 /tmp/c/d

then the returned list from C<guestfs_find> C</tmp> would be
4 elements:

 a
 b
 c
 c/d

If C<directory> is not a directory, then this command returns
an error.

The returned list is sorted.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_fsck

 int guestfs_fsck (guestfs_h *handle,
                const char *fstype,
                const char *device);

This runs the filesystem checker (fsck) on C<device> which
should have filesystem type C<fstype>.

The returned integer is the status.  See L<fsck(8)> for the
list of status codes from C<fsck>.

Notes:

=over 4

=item *

Multiple status codes can be summed together.

=item *

A non-zero return code can mean "success", for example if
errors have been corrected on the filesystem.

=item *

Checking or repairing NTFS volumes is not supported
(by linux-ntfs).

=back

This command is entirely equivalent to running C<fsck -a -t fstype device>.

On error this function returns -1.

=head2 guestfs_get_append

 const char *guestfs_get_append (guestfs_h *handle);

Return the additional kernel options which are added to the
guest kernel command line.

If C<NULL> then no options are added.

This function returns a string, or NULL on error.
The string is owned by the guest handle and must I<not> be freed.

=head2 guestfs_get_autosync

 int guestfs_get_autosync (guestfs_h *handle);

Get the autosync flag.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_get_e2label

 char *guestfs_get_e2label (guestfs_h *handle,
                const char *device);

This returns the ext2/3/4 filesystem label of the filesystem on
C<device>.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_get_e2uuid

 char *guestfs_get_e2uuid (guestfs_h *handle,
                const char *device);

This returns the ext2/3/4 filesystem UUID of the filesystem on
C<device>.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_get_memsize

 int guestfs_get_memsize (guestfs_h *handle);

This gets the memory size in megabytes allocated to the
qemu subprocess.

If C<guestfs_set_memsize> was not called
on this handle, and if C<LIBGUESTFS_MEMSIZE> was not set,
then this returns the compiled-in default value for memsize.

For more information on the architecture of libguestfs,
see L<guestfs(3)>.

On error this function returns -1.

=head2 guestfs_get_path

 const char *guestfs_get_path (guestfs_h *handle);

Return the current search path.

This is always non-NULL.  If it wasn't set already, then this will
return the default path.

This function returns a string, or NULL on error.
The string is owned by the guest handle and must I<not> be freed.

=head2 guestfs_get_qemu

 const char *guestfs_get_qemu (guestfs_h *handle);

Return the current qemu binary.

This is always non-NULL.  If it wasn't set already, then this will
return the default qemu binary name.

This function returns a string, or NULL on error.
The string is owned by the guest handle and must I<not> be freed.

=head2 guestfs_get_state

 int guestfs_get_state (guestfs_h *handle);

This returns the current state as an opaque integer.  This is
only useful for printing debug and internal error messages.

For more information on states, see L<guestfs(3)>.

On error this function returns -1.

=head2 guestfs_get_verbose

 int guestfs_get_verbose (guestfs_h *handle);

This returns the verbose messages flag.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_glob_expand

 char **guestfs_glob_expand (guestfs_h *handle,
                const char *pattern);

This command searches for all the pathnames matching
C<pattern> according to the wildcard expansion rules
used by the shell.

If no paths match, then this returns an empty list
(note: not an error).

It is just a wrapper around the C L<glob(3)> function
with flags C<GLOB_MARK|GLOB_BRACE>.
See that manual page for more details.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_grub_install

 int guestfs_grub_install (guestfs_h *handle,
                const char *root,
                const char *device);

This command installs GRUB (the Grand Unified Bootloader) on
C<device>, with the root directory being C<root>.

This function returns 0 on success or -1 on error.

=head2 guestfs_head

 char **guestfs_head (guestfs_h *handle,
                const char *path);

This command returns up to the first 10 lines of a file as
a list of strings.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_head_n

 char **guestfs_head_n (guestfs_h *handle,
                int nrlines,
                const char *path);

If the parameter C<nrlines> is a positive number, this returns the first
C<nrlines> lines of the file C<path>.

If the parameter C<nrlines> is a negative number, this returns lines
from the file C<path>, excluding the last C<nrlines> lines.

If the parameter C<nrlines> is zero, this returns an empty list.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_hexdump

 char *guestfs_hexdump (guestfs_h *handle,
                const char *path);

This runs C<hexdump -C> on the given C<path>.  The result is
the human-readable, canonical hex dump of the file.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_initrd_list

 char **guestfs_initrd_list (guestfs_h *handle,
                const char *path);

This command lists out files contained in an initrd.

The files are listed without any initial C</> character.  The
files are listed in the order they appear (not necessarily
alphabetical).  Directory names are listed as separate items.

Old Linux kernels (2.4 and earlier) used a compressed ext2
filesystem as initrd.  We I<only> support the newer initramfs
format (compressed cpio files).

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_is_busy

 int guestfs_is_busy (guestfs_h *handle);

This returns true iff this handle is busy processing a command
(in the C<BUSY> state).

For more information on states, see L<guestfs(3)>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_is_config

 int guestfs_is_config (guestfs_h *handle);

This returns true iff this handle is being configured
(in the C<CONFIG> state).

For more information on states, see L<guestfs(3)>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_is_dir

 int guestfs_is_dir (guestfs_h *handle,
                const char *path);

This returns C<true> if and only if there is a directory
with the given C<path> name.  Note that it returns false for
other objects like files.

See also C<guestfs_stat>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_is_file

 int guestfs_is_file (guestfs_h *handle,
                const char *path);

This returns C<true> if and only if there is a file
with the given C<path> name.  Note that it returns false for
other objects like directories.

See also C<guestfs_stat>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_is_launching

 int guestfs_is_launching (guestfs_h *handle);

This returns true iff this handle is launching the subprocess
(in the C<LAUNCHING> state).

For more information on states, see L<guestfs(3)>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_is_ready

 int guestfs_is_ready (guestfs_h *handle);

This returns true iff this handle is ready to accept commands
(in the C<READY> state).

For more information on states, see L<guestfs(3)>.

This function returns a C truth value on success or -1 on error.

=head2 guestfs_kill_subprocess

 int guestfs_kill_subprocess (guestfs_h *handle);

This kills the qemu subprocess.  You should never need to call this.

This function returns 0 on success or -1 on error.

=head2 guestfs_launch

 int guestfs_launch (guestfs_h *handle);

Internally libguestfs is implemented by running a virtual machine
using L<qemu(1)>.

You should call this after configuring the handle
(eg. adding drives) but before performing any actions.

This function returns 0 on success or -1 on error.

=head2 guestfs_list_devices

 char **guestfs_list_devices (guestfs_h *handle);

List all the block devices.

The full block device names are returned, eg. C</dev/sda>

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_list_partitions

 char **guestfs_list_partitions (guestfs_h *handle);

List all the partitions detected on all block devices.

The full partition device names are returned, eg. C</dev/sda1>

This does not return logical volumes.  For that you will need to
call C<guestfs_lvs>.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_ll

 char *guestfs_ll (guestfs_h *handle,
                const char *directory);

List the files in C<directory> (relative to the root directory,
there is no cwd) in the format of 'ls -la'.

This command is mostly useful for interactive sessions.  It
is I<not> intended that you try to parse the output string.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_ls

 char **guestfs_ls (guestfs_h *handle,
                const char *directory);

List the files in C<directory> (relative to the root directory,
there is no cwd).  The '.' and '..' entries are not returned, but
hidden files are shown.

This command is mostly useful for interactive sessions.  Programs
should probably use C<guestfs_readdir> instead.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_lstat

 struct guestfs_stat *guestfs_lstat (guestfs_h *handle,
                const char *path);

Returns file information for the given C<path>.

This is the same as C<guestfs_stat> except that if C<path>
is a symbolic link, then the link is stat-ed, not the file it
refers to.

This is the same as the C<lstat(2)> system call.

This function returns a C<struct guestfs_stat *>
(see L<stat(2)> and E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<free> after use>.

=head2 guestfs_lvcreate

 int guestfs_lvcreate (guestfs_h *handle,
                const char *logvol,
                const char *volgroup,
                int mbytes);

This creates an LVM volume group called C<logvol>
on the volume group C<volgroup>, with C<size> megabytes.

This function returns 0 on success or -1 on error.

=head2 guestfs_lvm_remove_all

 int guestfs_lvm_remove_all (guestfs_h *handle);

This command removes all LVM logical volumes, volume groups
and physical volumes.

This function returns 0 on success or -1 on error.

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=head2 guestfs_lvremove

 int guestfs_lvremove (guestfs_h *handle,
                const char *device);

Remove an LVM logical volume C<device>, where C<device> is
the path to the LV, such as C</dev/VG/LV>.

You can also remove all LVs in a volume group by specifying
the VG name, C</dev/VG>.

This function returns 0 on success or -1 on error.

=head2 guestfs_lvresize

 int guestfs_lvresize (guestfs_h *handle,
                const char *device,
                int mbytes);

This resizes (expands or shrinks) an existing LVM logical
volume to C<mbytes>.  When reducing, data in the reduced part
is lost.

This function returns 0 on success or -1 on error.

=head2 guestfs_lvs

 char **guestfs_lvs (guestfs_h *handle);

List all the logical volumes detected.  This is the equivalent
of the L<lvs(8)> command.

This returns a list of the logical volume device names
(eg. C</dev/VolGroup00/LogVol00>).

See also C<guestfs_lvs_full>.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_lvs_full

 struct guestfs_lvm_lv_list *guestfs_lvs_full (guestfs_h *handle);

List all the logical volumes detected.  This is the equivalent
of the L<lvs(8)> command.  The "full" version includes all fields.

This function returns a C<struct guestfs_lvm_lv_list *>
(see E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<guestfs_free_lvm_lv_list> after use>.

=head2 guestfs_mkdir

 int guestfs_mkdir (guestfs_h *handle,
                const char *path);

Create a directory named C<path>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkdir_p

 int guestfs_mkdir_p (guestfs_h *handle,
                const char *path);

Create a directory named C<path>, creating any parent directories
as necessary.  This is like the C<mkdir -p> shell command.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkdtemp

 char *guestfs_mkdtemp (guestfs_h *handle,
                const char *template);

This command creates a temporary directory.  The
C<template> parameter should be a full pathname for the
temporary directory name with the final six characters being
"XXXXXX".

For example: "/tmp/myprogXXXXXX" or "/Temp/myprogXXXXXX",
the second one being suitable for Windows filesystems.

The name of the temporary directory that was created
is returned.

The temporary directory is created with mode 0700
and is owned by root.

The caller is responsible for deleting the temporary
directory and its contents after use.

See also: L<mkdtemp(3)>

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_mkfifo

 int guestfs_mkfifo (guestfs_h *handle,
                int mode,
                const char *path);

This call creates a FIFO (named pipe) called C<path> with
mode C<mode>.  It is just a convenient wrapper around
C<guestfs_mknod>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkfs

 int guestfs_mkfs (guestfs_h *handle,
                const char *fstype,
                const char *device);

This creates a filesystem on C<device> (usually a partition
or LVM logical volume).  The filesystem type is C<fstype>, for
example C<ext3>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mknod

 int guestfs_mknod (guestfs_h *handle,
                int mode,
                int devmajor,
                int devminor,
                const char *path);

This call creates block or character special devices, or
named pipes (FIFOs).

The C<mode> parameter should be the mode, using the standard
constants.  C<devmajor> and C<devminor> are the
device major and minor numbers, only used when creating block
and character special devices.

This function returns 0 on success or -1 on error.

=head2 guestfs_mknod_b

 int guestfs_mknod_b (guestfs_h *handle,
                int mode,
                int devmajor,
                int devminor,
                const char *path);

This call creates a block device node called C<path> with
mode C<mode> and device major/minor C<devmajor> and C<devminor>.
It is just a convenient wrapper around C<guestfs_mknod>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mknod_c

 int guestfs_mknod_c (guestfs_h *handle,
                int mode,
                int devmajor,
                int devminor,
                const char *path);

This call creates a char device node called C<path> with
mode C<mode> and device major/minor C<devmajor> and C<devminor>.
It is just a convenient wrapper around C<guestfs_mknod>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkswap

 int guestfs_mkswap (guestfs_h *handle,
                const char *device);

Create a swap partition on C<device>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkswap_L

 int guestfs_mkswap_L (guestfs_h *handle,
                const char *label,
                const char *device);

Create a swap partition on C<device> with label C<label>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mkswap_U

 int guestfs_mkswap_U (guestfs_h *handle,
                const char *uuid,
                const char *device);

Create a swap partition on C<device> with UUID C<uuid>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mount

 int guestfs_mount (guestfs_h *handle,
                const char *device,
                const char *mountpoint);

Mount a guest disk at a position in the filesystem.  Block devices
are named C</dev/sda>, C</dev/sdb> and so on, as they were added to
the guest.  If those block devices contain partitions, they will have
the usual names (eg. C</dev/sda1>).  Also LVM C</dev/VG/LV>-style
names can be used.

The rules are the same as for L<mount(2)>:  A filesystem must
first be mounted on C</> before others can be mounted.  Other
filesystems can only be mounted on directories which already
exist.

The mounted filesystem is writable, if we have sufficient permissions
on the underlying device.

The filesystem options C<sync> and C<noatime> are set with this
call, in order to improve reliability.

This function returns 0 on success or -1 on error.

=head2 guestfs_mount_loop

 int guestfs_mount_loop (guestfs_h *handle,
                const char *file,
                const char *mountpoint);

This command lets you mount C<file> (a filesystem image
in a file) on a mount point.  It is entirely equivalent to
the command C<mount -o loop file mountpoint>.

This function returns 0 on success or -1 on error.

=head2 guestfs_mount_options

 int guestfs_mount_options (guestfs_h *handle,
                const char *options,
                const char *device,
                const char *mountpoint);

This is the same as the C<guestfs_mount> command, but it
allows you to set the mount options as for the
L<mount(8)> I<-o> flag.

This function returns 0 on success or -1 on error.

=head2 guestfs_mount_ro

 int guestfs_mount_ro (guestfs_h *handle,
                const char *device,
                const char *mountpoint);

This is the same as the C<guestfs_mount> command, but it
mounts the filesystem with the read-only (I<-o ro>) flag.

This function returns 0 on success or -1 on error.

=head2 guestfs_mount_vfs

 int guestfs_mount_vfs (guestfs_h *handle,
                const char *options,
                const char *vfstype,
                const char *device,
                const char *mountpoint);

This is the same as the C<guestfs_mount> command, but it
allows you to set both the mount options and the vfstype
as for the L<mount(8)> I<-o> and I<-t> flags.

This function returns 0 on success or -1 on error.

=head2 guestfs_mounts

 char **guestfs_mounts (guestfs_h *handle);

This returns the list of currently mounted filesystems.  It returns
the list of devices (eg. C</dev/sda1>, C</dev/VG/LV>).

Some internal mounts are not shown.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_mv

 int guestfs_mv (guestfs_h *handle,
                const char *src,
                const char *dest);

This moves a file from C<src> to C<dest> where C<dest> is
either a destination filename or destination directory.

This function returns 0 on success or -1 on error.

=head2 guestfs_ntfs_3g_probe

 int guestfs_ntfs_3g_probe (guestfs_h *handle,
                int rw,
                const char *device);

This command runs the L<ntfs-3g.probe(8)> command which probes
an NTFS C<device> for mountability.  (Not all NTFS volumes can
be mounted read-write, and some cannot be mounted at all).

C<rw> is a boolean flag.  Set it to true if you want to test
if the volume can be mounted read-write.  Set it to false if
you want to test if the volume can be mounted read-only.

The return value is an integer which C<0> if the operation
would succeed, or some non-zero value documented in the
L<ntfs-3g.probe(8)> manual page.

On error this function returns -1.

=head2 guestfs_ping_daemon

 int guestfs_ping_daemon (guestfs_h *handle);

This is a test probe into the guestfs daemon running inside
the qemu subprocess.  Calling this function checks that the
daemon responds to the ping message, without affecting the daemon
or attached block device(s) in any other way.

This function returns 0 on success or -1 on error.

=head2 guestfs_pvcreate

 int guestfs_pvcreate (guestfs_h *handle,
                const char *device);

This creates an LVM physical volume on the named C<device>,
where C<device> should usually be a partition name such
as C</dev/sda1>.

This function returns 0 on success or -1 on error.

=head2 guestfs_pvremove

 int guestfs_pvremove (guestfs_h *handle,
                const char *device);

This wipes a physical volume C<device> so that LVM will no longer
recognise it.

The implementation uses the C<pvremove> command which refuses to
wipe physical volumes that contain any volume groups, so you have
to remove those first.

This function returns 0 on success or -1 on error.

=head2 guestfs_pvresize

 int guestfs_pvresize (guestfs_h *handle,
                const char *device);

This resizes (expands or shrinks) an existing LVM physical
volume to match the new size of the underlying device.

This function returns 0 on success or -1 on error.

=head2 guestfs_pvs

 char **guestfs_pvs (guestfs_h *handle);

List all the physical volumes detected.  This is the equivalent
of the L<pvs(8)> command.

This returns a list of just the device names that contain
PVs (eg. C</dev/sda2>).

See also C<guestfs_pvs_full>.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_pvs_full

 struct guestfs_lvm_pv_list *guestfs_pvs_full (guestfs_h *handle);

List all the physical volumes detected.  This is the equivalent
of the L<pvs(8)> command.  The "full" version includes all fields.

This function returns a C<struct guestfs_lvm_pv_list *>
(see E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<guestfs_free_lvm_pv_list> after use>.

=head2 guestfs_read_lines

 char **guestfs_read_lines (guestfs_h *handle,
                const char *path);

Return the contents of the file named C<path>.

The file contents are returned as a list of lines.  Trailing
C<LF> and C<CRLF> character sequences are I<not> returned.

Note that this function cannot correctly handle binary files
(specifically, files containing C<\0> character which is treated
as end of line).  For those you need to use the C<guestfs_read_file>
function which has a more complex interface.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_resize2fs

 int guestfs_resize2fs (guestfs_h *handle,
                const char *device);

This resizes an ext2 or ext3 filesystem to match the size of
the underlying device.

I<Note:> It is sometimes required that you run C<guestfs_e2fsck_f>
on the C<device> before calling this command.  For unknown reasons
C<resize2fs> sometimes gives an error about this and sometimes not.
In any case, it is always safe to call C<guestfs_e2fsck_f> before
calling this function.

This function returns 0 on success or -1 on error.

=head2 guestfs_rm

 int guestfs_rm (guestfs_h *handle,
                const char *path);

Remove the single file C<path>.

This function returns 0 on success or -1 on error.

=head2 guestfs_rm_rf

 int guestfs_rm_rf (guestfs_h *handle,
                const char *path);

Remove the file or directory C<path>, recursively removing the
contents if its a directory.  This is like the C<rm -rf> shell
command.

This function returns 0 on success or -1 on error.

=head2 guestfs_rmdir

 int guestfs_rmdir (guestfs_h *handle,
                const char *path);

Remove the single directory C<path>.

This function returns 0 on success or -1 on error.

=head2 guestfs_scrub_device

 int guestfs_scrub_device (guestfs_h *handle,
                const char *device);

This command writes patterns over C<device> to make data retrieval
more difficult.

It is an interface to the L<scrub(1)> program.  See that
manual page for more details.

This function returns 0 on success or -1 on error.

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=head2 guestfs_scrub_file

 int guestfs_scrub_file (guestfs_h *handle,
                const char *file);

This command writes patterns over a file to make data retrieval
more difficult.

The file is I<removed> after scrubbing.

It is an interface to the L<scrub(1)> program.  See that
manual page for more details.

This function returns 0 on success or -1 on error.

=head2 guestfs_scrub_freespace

 int guestfs_scrub_freespace (guestfs_h *handle,
                const char *dir);

This command creates the directory C<dir> and then fills it
with files until the filesystem is full, and scrubs the files
as for C<guestfs_scrub_file>, and deletes them.
The intention is to scrub any free space on the partition
containing C<dir>.

It is an interface to the L<scrub(1)> program.  See that
manual page for more details.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_append

 int guestfs_set_append (guestfs_h *handle,
                const char *append);

This function is used to add additional options to the
guest kernel command line.

The default is C<NULL> unless overridden by setting
C<LIBGUESTFS_APPEND> environment variable.

Setting C<append> to C<NULL> means I<no> additional options
are passed (libguestfs always adds a few of its own).

This function returns 0 on success or -1 on error.

=head2 guestfs_set_autosync

 int guestfs_set_autosync (guestfs_h *handle,
                int autosync);

If C<autosync> is true, this enables autosync.  Libguestfs will make a
best effort attempt to run C<guestfs_umount_all> followed by
C<guestfs_sync> when the handle is closed
(also if the program exits without closing handles).

This is disabled by default (except in guestfish where it is
enabled by default).

This function returns 0 on success or -1 on error.

=head2 guestfs_set_busy

 int guestfs_set_busy (guestfs_h *handle);

This sets the state to C<BUSY>.  This is only used when implementing
actions using the low-level API.

For more information on states, see L<guestfs(3)>.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_e2label

 int guestfs_set_e2label (guestfs_h *handle,
                const char *device,
                const char *label);

This sets the ext2/3/4 filesystem label of the filesystem on
C<device> to C<label>.  Filesystem labels are limited to
16 characters.

You can use either C<guestfs_tune2fs_l> or C<guestfs_get_e2label>
to return the existing label on a filesystem.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_e2uuid

 int guestfs_set_e2uuid (guestfs_h *handle,
                const char *device,
                const char *uuid);

This sets the ext2/3/4 filesystem UUID of the filesystem on
C<device> to C<uuid>.  The format of the UUID and alternatives
such as C<clear>, C<random> and C<time> are described in the
L<tune2fs(8)> manpage.

You can use either C<guestfs_tune2fs_l> or C<guestfs_get_e2uuid>
to return the existing UUID of a filesystem.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_memsize

 int guestfs_set_memsize (guestfs_h *handle,
                int memsize);

This sets the memory size in megabytes allocated to the
qemu subprocess.  This only has any effect if called before
C<guestfs_launch>.

You can also change this by setting the environment
variable C<LIBGUESTFS_MEMSIZE> before the handle is
created.

For more information on the architecture of libguestfs,
see L<guestfs(3)>.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_path

 int guestfs_set_path (guestfs_h *handle,
                const char *path);

Set the path that libguestfs searches for kernel and initrd.img.

The default is C<$libdir/guestfs> unless overridden by setting
C<LIBGUESTFS_PATH> environment variable.

Setting C<path> to C<NULL> restores the default path.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_qemu

 int guestfs_set_qemu (guestfs_h *handle,
                const char *qemu);

Set the qemu binary that we will use.

The default is chosen when the library was compiled by the
configure script.

You can also override this by setting the C<LIBGUESTFS_QEMU>
environment variable.

Setting C<qemu> to C<NULL> restores the default qemu binary.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_ready

 int guestfs_set_ready (guestfs_h *handle);

This sets the state to C<READY>.  This is only used when implementing
actions using the low-level API.

For more information on states, see L<guestfs(3)>.

This function returns 0 on success or -1 on error.

=head2 guestfs_set_verbose

 int guestfs_set_verbose (guestfs_h *handle,
                int verbose);

If C<verbose> is true, this turns on verbose messages (to C<stderr>).

Verbose messages are disabled unless the environment variable
C<LIBGUESTFS_DEBUG> is defined and set to C<1>.

This function returns 0 on success or -1 on error.

=head2 guestfs_sfdisk

 int guestfs_sfdisk (guestfs_h *handle,
                const char *device,
                int cyls,
                int heads,
                int sectors,
                char * const* const lines);

This is a direct interface to the L<sfdisk(8)> program for creating
partitions on block devices.

C<device> should be a block device, for example C</dev/sda>.

C<cyls>, C<heads> and C<sectors> are the number of cylinders, heads
and sectors on the device, which are passed directly to sfdisk as
the I<-C>, I<-H> and I<-S> parameters.  If you pass C<0> for any
of these, then the corresponding parameter is omitted.  Usually for
'large' disks, you can just pass C<0> for these, but for small
(floppy-sized) disks, sfdisk (or rather, the kernel) cannot work
out the right geometry and you will need to tell it.

C<lines> is a list of lines that we feed to C<sfdisk>.  For more
information refer to the L<sfdisk(8)> manpage.

To create a single partition occupying the whole disk, you would
pass C<lines> as a single element list, when the single element being
the string C<,> (comma).

See also: C<guestfs_sfdisk_l>, C<guestfs_sfdisk_N>

This function returns 0 on success or -1 on error.

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=head2 guestfs_sfdisk_N

 int guestfs_sfdisk_N (guestfs_h *handle,
                const char *device,
                int partnum,
                int cyls,
                int heads,
                int sectors,
                const char *line);

This runs L<sfdisk(8)> option to modify just the single
partition C<n> (note: C<n> counts from 1).

For other parameters, see C<guestfs_sfdisk>.  You should usually
pass C<0> for the cyls/heads/sectors parameters.

This function returns 0 on success or -1 on error.

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=head2 guestfs_sfdisk_disk_geometry

 char *guestfs_sfdisk_disk_geometry (guestfs_h *handle,
                const char *device);

This displays the disk geometry of C<device> read from the
partition table.  Especially in the case where the underlying
block device has been resized, this can be different from the
kernel's idea of the geometry (see C<guestfs_sfdisk_kernel_geometry>).

The result is in human-readable format, and not designed to
be parsed.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_sfdisk_kernel_geometry

 char *guestfs_sfdisk_kernel_geometry (guestfs_h *handle,
                const char *device);

This displays the kernel's idea of the geometry of C<device>.

The result is in human-readable format, and not designed to
be parsed.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_sfdisk_l

 char *guestfs_sfdisk_l (guestfs_h *handle,
                const char *device);

This displays the partition table on C<device>, in the
human-readable output of the L<sfdisk(8)> command.  It is
not intended to be parsed.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_sh

 char *guestfs_sh (guestfs_h *handle,
                const char *command);

This call runs a command from the guest filesystem via the
guest's C</bin/sh>.

This is like C<guestfs_command>, but passes the command to:

 /bin/sh -c "command"

Depending on the guest's shell, this usually results in
wildcards being expanded, shell expressions being interpolated
and so on.

All the provisos about C<guestfs_command> apply to this call.

This function returns a string, or NULL on error.
I<The caller must free the returned string after use>.

=head2 guestfs_sh_lines

 char **guestfs_sh_lines (guestfs_h *handle,
                const char *command);

This is the same as C<guestfs_sh>, but splits the result
into a list of lines.

See also: C<guestfs_command_lines>

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_sleep

 int guestfs_sleep (guestfs_h *handle,
                int secs);

Sleep for C<secs> seconds.

This function returns 0 on success or -1 on error.

=head2 guestfs_stat

 struct guestfs_stat *guestfs_stat (guestfs_h *handle,
                const char *path);

Returns file information for the given C<path>.

This is the same as the C<stat(2)> system call.

This function returns a C<struct guestfs_stat *>
(see L<stat(2)> and E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<free> after use>.

=head2 guestfs_statvfs

 struct guestfs_statvfs *guestfs_statvfs (guestfs_h *handle,
                const char *path);

Returns file system statistics for any mounted file system.
C<path> should be a file or directory in the mounted file system
(typically it is the mount point itself, but it doesn't need to be).

This is the same as the C<statvfs(2)> system call.

This function returns a C<struct guestfs_statvfs *>
(see L<statvfs(2)> and E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<free> after use>.

=head2 guestfs_strings

 char **guestfs_strings (guestfs_h *handle,
                const char *path);

This runs the L<strings(1)> command on a file and returns
the list of printable strings found.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_strings_e

 char **guestfs_strings_e (guestfs_h *handle,
                const char *encoding,
                const char *path);

This is like the C<guestfs_strings> command, but allows you to
specify the encoding.

See the L<strings(1)> manpage for the full list of encodings.

Commonly useful encodings are C<l> (lower case L) which will
show strings inside Windows/x86 files.

The returned strings are transcoded to UTF-8.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_sync

 int guestfs_sync (guestfs_h *handle);

This syncs the disk, so that any writes are flushed through to the
underlying disk image.

You should always call this if you have modified a disk image, before
closing the handle.

This function returns 0 on success or -1 on error.

=head2 guestfs_tail

 char **guestfs_tail (guestfs_h *handle,
                const char *path);

This command returns up to the last 10 lines of a file as
a list of strings.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_tail_n

 char **guestfs_tail_n (guestfs_h *handle,
                int nrlines,
                const char *path);

If the parameter C<nrlines> is a positive number, this returns the last
C<nrlines> lines of the file C<path>.

If the parameter C<nrlines> is a negative number, this returns lines
from the file C<path>, starting with the C<-nrlines>th line.

If the parameter C<nrlines> is zero, this returns an empty list.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_tar_in

 int guestfs_tar_in (guestfs_h *handle,
                const char *tarfile,
                const char *directory);

This command uploads and unpacks local file C<tarfile> (an
I<uncompressed> tar file) into C<directory>.

To upload a compressed tarball, use C<guestfs_tgz_in>.

This function returns 0 on success or -1 on error.

=head2 guestfs_tar_out

 int guestfs_tar_out (guestfs_h *handle,
                const char *directory,
                const char *tarfile);

This command packs the contents of C<directory> and downloads
it to local file C<tarfile>.

To download a compressed tarball, use C<guestfs_tgz_out>.

This function returns 0 on success or -1 on error.

=head2 guestfs_tgz_in

 int guestfs_tgz_in (guestfs_h *handle,
                const char *tarball,
                const char *directory);

This command uploads and unpacks local file C<tarball> (a
I<gzip compressed> tar file) into C<directory>.

To upload an uncompressed tarball, use C<guestfs_tar_in>.

This function returns 0 on success or -1 on error.

=head2 guestfs_tgz_out

 int guestfs_tgz_out (guestfs_h *handle,
                const char *directory,
                const char *tarball);

This command packs the contents of C<directory> and downloads
it to local file C<tarball>.

To download an uncompressed tarball, use C<guestfs_tar_out>.

This function returns 0 on success or -1 on error.

=head2 guestfs_touch

 int guestfs_touch (guestfs_h *handle,
                const char *path);

Touch acts like the L<touch(1)> command.  It can be used to
update the timestamps on a file, or, if the file does not exist,
to create a new zero-length file.

This function returns 0 on success or -1 on error.

=head2 guestfs_tune2fs_l

 char **guestfs_tune2fs_l (guestfs_h *handle,
                const char *device);

This returns the contents of the ext2, ext3 or ext4 filesystem
superblock on C<device>.

It is the same as running C<tune2fs -l device>.  See L<tune2fs(8)>
manpage for more details.  The list of fields returned isn't
clearly defined, and depends on both the version of C<tune2fs>
that libguestfs was built against, and the filesystem itself.

This function returns a NULL-terminated array of
strings, or NULL if there was an error.
The array of strings will always have length C<2n+1>, where
C<n> keys and values alternate, followed by the trailing NULL entry.
I<The caller must free the strings and the array after use>.

=head2 guestfs_umask

 int guestfs_umask (guestfs_h *handle,
                int mask);

This function sets the mask used for creating new files and
device nodes to C<mask & 0777>.

Typical umask values would be C<022> which creates new files
with permissions like "-rw-r--r--" or "-rwxr-xr-x", and
C<002> which creates new files with permissions like
"-rw-rw-r--" or "-rwxrwxr-x".

The default umask is C<022>.  This is important because it
means that directories and device nodes will be created with
C<0644> or C<0755> mode even if you specify C<0777>.

See also L<umask(2)>, C<guestfs_mknod>, C<guestfs_mkdir>.

This call returns the previous umask.

On error this function returns -1.

=head2 guestfs_umount

 int guestfs_umount (guestfs_h *handle,
                const char *pathordevice);

This unmounts the given filesystem.  The filesystem may be
specified either by its mountpoint (path) or the device which
contains the filesystem.

This function returns 0 on success or -1 on error.

=head2 guestfs_umount_all

 int guestfs_umount_all (guestfs_h *handle);

This unmounts all mounted filesystems.

Some internal mounts are not unmounted by this call.

This function returns 0 on success or -1 on error.

=head2 guestfs_upload

 int guestfs_upload (guestfs_h *handle,
                const char *filename,
                const char *remotefilename);

Upload local file C<filename> to C<remotefilename> on the
filesystem.

C<filename> can also be a named pipe.

See also C<guestfs_download>.

This function returns 0 on success or -1 on error.

=head2 guestfs_vg_activate

 int guestfs_vg_activate (guestfs_h *handle,
                int activate,
                char * const* const volgroups);

This command activates or (if C<activate> is false) deactivates
all logical volumes in the listed volume groups C<volgroups>.
If activated, then they are made known to the
kernel, ie. they appear as C</dev/mapper> devices.  If deactivated,
then those devices disappear.

This command is the same as running C<vgchange -a y|n volgroups...>

Note that if C<volgroups> is an empty list then B<all> volume groups
are activated or deactivated.

This function returns 0 on success or -1 on error.

=head2 guestfs_vg_activate_all

 int guestfs_vg_activate_all (guestfs_h *handle,
                int activate);

This command activates or (if C<activate> is false) deactivates
all logical volumes in all volume groups.
If activated, then they are made known to the
kernel, ie. they appear as C</dev/mapper> devices.  If deactivated,
then those devices disappear.

This command is the same as running C<vgchange -a y|n>

This function returns 0 on success or -1 on error.

=head2 guestfs_vgcreate

 int guestfs_vgcreate (guestfs_h *handle,
                const char *volgroup,
                char * const* const physvols);

This creates an LVM volume group called C<volgroup>
from the non-empty list of physical volumes C<physvols>.

This function returns 0 on success or -1 on error.

=head2 guestfs_vgremove

 int guestfs_vgremove (guestfs_h *handle,
                const char *vgname);

Remove an LVM volume group C<vgname>, (for example C<VG>).

This also forcibly removes all logical volumes in the volume
group (if any).

This function returns 0 on success or -1 on error.

=head2 guestfs_vgs

 char **guestfs_vgs (guestfs_h *handle);

List all the volumes groups detected.  This is the equivalent
of the L<vgs(8)> command.

This returns a list of just the volume group names that were
detected (eg. C<VolGroup00>).

See also C<guestfs_vgs_full>.

This function returns a NULL-terminated array of strings
(like L<environ(3)>), or NULL if there was an error.
I<The caller must free the strings and the array after use>.

=head2 guestfs_vgs_full

 struct guestfs_lvm_vg_list *guestfs_vgs_full (guestfs_h *handle);

List all the volumes groups detected.  This is the equivalent
of the L<vgs(8)> command.  The "full" version includes all fields.

This function returns a C<struct guestfs_lvm_vg_list *>
(see E<lt>guestfs-structs.hE<gt>),
or NULL if there was an error.
I<The caller must call C<guestfs_free_lvm_vg_list> after use>.

=head2 guestfs_wait_ready

 int guestfs_wait_ready (guestfs_h *handle);

Internally libguestfs is implemented by running a virtual machine
using L<qemu(1)>.

You should call this after C<guestfs_launch> to wait for the launch
to complete.

This function returns 0 on success or -1 on error.

=head2 guestfs_wc_c

 int guestfs_wc_c (guestfs_h *handle,
                const char *path);

This command counts the characters in a file, using the
C<wc -c> external command.

On error this function returns -1.

=head2 guestfs_wc_l

 int guestfs_wc_l (guestfs_h *handle,
                const char *path);

This command counts the lines in a file, using the
C<wc -l> external command.

On error this function returns -1.

=head2 guestfs_wc_w

 int guestfs_wc_w (guestfs_h *handle,
                const char *path);

This command counts the words in a file, using the
C<wc -w> external command.

On error this function returns -1.

=head2 guestfs_write_file

 int guestfs_write_file (guestfs_h *handle,
                const char *path,
                const char *content,
                int size);

This call creates a file called C<path>.  The contents of the
file is the string C<content> (which can contain any 8 bit data),
with length C<size>.

As a special case, if C<size> is C<0>
then the length is calculated using C<strlen> (so in this case
the content cannot contain embedded ASCII NULs).

I<NB.> Owing to a bug, writing content containing ASCII NUL
characters does I<not> work, even if the length is specified.
We hope to resolve this bug in a future version.  In the meantime
use C<guestfs_upload>.

This function returns 0 on success or -1 on error.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=head2 guestfs_zero

 int guestfs_zero (guestfs_h *handle,
                const char *device);

This command writes zeroes over the first few blocks of C<device>.

How many blocks are zeroed isn't specified (but it's I<not> enough
to securely wipe the device).  It should be sufficient to remove
any partition tables, filesystem superblocks and so on.

See also: C<guestfs_scrub_device>.

This function returns 0 on success or -1 on error.

=head2 guestfs_zerofree

 int guestfs_zerofree (guestfs_h *handle,
                const char *device);

This runs the I<zerofree> program on C<device>.  This program
claims to zero unused inodes and disk blocks on an ext2/3
filesystem, thus making it possible to compress the filesystem
more effectively.

You should B<not> run this program if the filesystem is
mounted.

It is possible that using this program can damage the filesystem
or data on the filesystem.

This function returns 0 on success or -1 on error.