--- /dev/null
+======================
+ Library architecture
+======================
+
+Ceph is structured into libraries which are built and then combined together to
+make executables and other libraries.
+
+- libcommon: a collection of utilities which are available to nearly every ceph
+ library and executable. In general, libcommon should not contain global
+ variables, because it is intended to be linked into libraries such as
+ libcephfs.so.
+
+- libglobal: a collection of utilities focused on the needs of Ceph daemon
+ programs. In here you will find pidfile management functions, signal
+ handlers, and so forth.
+
+.. todo:: document other libraries
+