Turn ProtocolLimitWarning into link to documentation section.

[libguestfs.git] / src / guestfs.pod

diff --git a/src/guestfs.pod b/src/guestfs.pod
index 7f810f3..514db03 100644 (file)
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -33,7 +33,8 @@ schemes, qcow, qcow2, vmdk.
 
 Libguestfs provides ways to enumerate guest storage (eg. partitions,
 LVs, what filesystem is in each LV, etc.).  It can also run commands
 
 Libguestfs provides ways to enumerate guest storage (eg. partitions,
 LVs, what filesystem is in each LV, etc.).  It can also run commands

-in the context of the guest.  Also you can access filesystems over FTP.
+in the context of the guest.  Also you can access filesystems over
+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,


@@ -588,6 +589,29 @@ C<guestfish -c command> to run commands.
 
 =back
 
 
 =back
 

+=head2 PROTOCOL LIMITS
+
+Internally libguestfs uses a message-based protocol to pass API calls
+and their responses to and from a small "appliance" (see L</INTERNALS>
+for plenty more detail about this).  The maximum message size used by
+the protocol is slightly less than 4 MB.  For some API calls you may
+need to be aware of this limit.  The API calls which may be affected
+are individually documented, with a link back to this section of the
+documentation.
+
+A simple call such as C<guestfs_cat> returns its result (the file
+data) in a simple string.  Because this string is at some point
+internally encoded as a message, the maximum size that it can return
+is slightly under 4 MB.  If the requested file is larger than this
+then you will get an error.
+
+In order to transfer large files into and out of the guest filesystem,
+you need to use particular calls that support this.  The sections
+L</UPLOADING> and L</DOWNLOADING> document how to do this.
+
+You might also consider mounting the disk image using our FUSE
+filesystem support (L<guestmount(1)>).
+

 =head1 CONNECTION MANAGEMENT
 
 =head2 guestfs_h *
 =head1 CONNECTION MANAGEMENT
 
 =head2 guestfs_h *