ovsdb: Fix support for systems where libpcre is not installed.

[sliver-openvswitch.git] / INSTALL.Linux

diff --git a/INSTALL.Linux b/INSTALL.Linux
index 891fd23..6529118 100644 (file)
--- a/INSTALL.Linux
+++ b/INSTALL.Linux
@@ -27,8 +27,15 @@ you will need the following software:
       connections from an Open vSwitch to an OpenFlow controller.  To
       enable, configure with --enable-ssl=yes.
 
-To compile the kernel module (which is required for operation), you
-must also install the following:
+    - libpcre, the Perl Compatible Regular Expression library, is
+      optional but recommended.  Without it, OVSDB will not be able to
+      validate regular-expression based contraints.
+
+To compile the kernel module, you must also install the following.  If
+you cannot build or install the kernel module, you may use the
+userspace-only implementation, at a cost in performance.  The
+userspace implementation may also lack some features.  Refer to
+INSTALL.userspace for more information.
 
     - A supported Linux kernel version.  Please refer to README for a
       list of supported versions.
@@ -64,6 +71,8 @@ you will also need the following software:
 
     - pkg-config.  We test with version 0.22.
 
+    - Python 2.x, for x >= 4.
+
 Installation Requirements
 -------------------------
 
@@ -75,6 +84,9 @@ following software:
     - libssl compatible with the libssl used for build, if OpenSSL was
       used for the build.
 
+    - libpcre compatible with the libpcre used for build, if PCRE was
+      used for the build.
+
     - The Linux kernel version configured as part of the build.
 
     - For optional support of ingress policing, the "tc" program from