diff --git a/core/java/src/freenet/support/CPUInformation/CPUID.java b/core/java/src/freenet/support/CPUInformation/CPUID.java
index 58469c6d74..e145c3795f 100644
--- a/core/java/src/freenet/support/CPUInformation/CPUID.java
+++ b/core/java/src/freenet/support/CPUInformation/CPUID.java
@@ -10,6 +10,7 @@ import java.io.InputStream;
 import java.net.URL;
 
 import net.i2p.I2PAppContext;
+import net.i2p.util.FileUtil;
 
 /**
  * @author Iakin
@@ -484,8 +485,11 @@ public class CPUID {
      * 
      * <p>This is a pretty ugly hack, using the general technique illustrated by the
      * onion FEC libraries.  It works by pulling the resource, writing out the 
-     * byte stream to a temporary file, loading the native library from that file,
-     * then deleting the file.</p>
+     * byte stream to a temporary file, loading the native library from that file.
+     * We then attempt to copy the file from the temporary dir to the base install dir,
+     * so we don't have to do this next time - but we don't complain if it fails,
+     * so we transparently support read-only base dirs.
+     * </p>
      *
      * @return true if it was loaded successfully, else false
      *
@@ -503,9 +507,10 @@ public class CPUID {
 
         File outFile = null;
         FileOutputStream fos = null;
+        String filename = libPrefix + "jcpuid" + libSuffix;
         try {
             InputStream libStream = resource.openStream();
-            outFile = new File(I2PAppContext.getGlobalContext().getBaseDir(), libPrefix + "jcpuid" + libSuffix);
+            outFile = new File(I2PAppContext.getGlobalContext().getTempDir(), filename);
             fos = new FileOutputStream(outFile);
             // wtf this was 4096*1024 which is really excessive for a roughly 4KB file
             byte buf[] = new byte[4096];
@@ -517,7 +522,6 @@ public class CPUID {
             fos.close();
             fos = null;
             System.load(outFile.getAbsolutePath());//System.load requires an absolute path to the lib
-            return true;
         } catch (UnsatisfiedLinkError ule) {
             if (_doLog) {
                 System.err.println("ERROR: The resource " + resourceName 
@@ -536,6 +540,10 @@ public class CPUID {
                 try { fos.close(); } catch (IOException ioe) {}
             }
         }
+        // copy to install dir, ignore failure
+        File newFile = new File(I2PAppContext.getGlobalContext().getBaseDir(), filename);
+        FileUtil.copy(outFile.getAbsolutePath(), newFile.getAbsolutePath(), false, true);
+        return true;
     }
     
     private static final String getResourceName()
diff --git a/core/java/src/net/i2p/util/FileUtil.java b/core/java/src/net/i2p/util/FileUtil.java
index 05346ccfe2..b6140b6e43 100644
--- a/core/java/src/net/i2p/util/FileUtil.java
+++ b/core/java/src/net/i2p/util/FileUtil.java
@@ -201,9 +201,18 @@ public class FileUtil {
         }
     }
 
-    
-    /** return true if it was copied successfully */
+    /**
+      * @return true if it was copied successfully
+      */
     public static boolean copy(String source, String dest, boolean overwriteExisting) {
+        return copy(source, dest, overwriteExisting, false);
+    }
+
+    /**
+      * @param quiet don't log fails to wrapper log if true
+      * @return true if it was copied successfully
+      */
+    public static boolean copy(String source, String dest, boolean overwriteExisting, boolean quiet) {
         File src = new File(source);
         File dst = new File(dest);
 
@@ -226,7 +235,8 @@ public class FileUtil {
             out.close();
             return true;
         } catch (IOException ioe) {
-            ioe.printStackTrace();
+            if (!quiet)
+                ioe.printStackTrace();
             return false;
         }
     }
diff --git a/core/java/src/net/i2p/util/NativeBigInteger.java b/core/java/src/net/i2p/util/NativeBigInteger.java
index bafaa5e5c9..44101afd99 100644
--- a/core/java/src/net/i2p/util/NativeBigInteger.java
+++ b/core/java/src/net/i2p/util/NativeBigInteger.java
@@ -24,6 +24,7 @@ import freenet.support.CPUInformation.IntelCPUInfo;
 import freenet.support.CPUInformation.UnknownCPUException;
 
 import net.i2p.I2PAppContext;
+import net.i2p.util.FileUtil;
 import net.i2p.util.Log;
 
 /**
@@ -516,8 +517,11 @@ public class NativeBigInteger extends BigInteger {
      * 
      * <p>This is a pretty ugly hack, using the general technique illustrated by the
      * onion FEC libraries.  It works by pulling the resource, writing out the 
-     * byte stream to a temporary file, loading the native library from that file,
-     * then deleting the file.</p>
+     * byte stream to a temporary file, loading the native library from that file.
+     * We then attempt to copy the file from the temporary dir to the base install dir,
+     * so we don't have to do this next time - but we don't complain if it fails,
+     * so we transparently support read-only base dirs.
+     * </p>
      *
      * @return true if it was loaded successfully, else false
      *
@@ -538,9 +542,10 @@ public class NativeBigInteger extends BigInteger {
 
         File outFile = null;
         FileOutputStream fos = null;
+        String filename =  _libPrefix + "jbigi" + _libSuffix;
         try {
             InputStream libStream = resource.openStream();
-            outFile = new File(I2PAppContext.getGlobalContext().getBaseDir(), _libPrefix + "jbigi" + _libSuffix);
+            outFile = new File(I2PAppContext.getGlobalContext().getTempDir(), filename);
             fos = new FileOutputStream(outFile);
             // wtf this was 4096*1024 which is really excessive for a roughly 50KB file
             byte buf[] = new byte[4096];
@@ -552,7 +557,6 @@ public class NativeBigInteger extends BigInteger {
             fos.close();
             fos = null;
             System.load(outFile.getAbsolutePath()); //System.load requires an absolute path to the lib
-            return true;
         } catch (UnsatisfiedLinkError ule) {
             if (_doLog) {
                 System.err.println("ERROR: The resource " + resourceName 
@@ -571,6 +575,10 @@ public class NativeBigInteger extends BigInteger {
                 try { fos.close(); } catch (IOException ioe) {}
             }
         }
+        // copy to install dir, ignore failure
+        File newFile = new File(I2PAppContext.getGlobalContext().getBaseDir(), filename);
+        FileUtil.copy(outFile.getAbsolutePath(), newFile.getAbsolutePath(), false, true);
+        return true;
     }
     
     private static final String getResourceName(boolean optimized) {