diff --git a/apps/routerconsole/java/src/net/i2p/router/update/ConsoleUpdateManager.java b/apps/routerconsole/java/src/net/i2p/router/update/ConsoleUpdateManager.java
index 1d97872e0..537d37041 100644
--- a/apps/routerconsole/java/src/net/i2p/router/update/ConsoleUpdateManager.java
+++ b/apps/routerconsole/java/src/net/i2p/router/update/ConsoleUpdateManager.java
@@ -172,6 +172,7 @@ public class ConsoleUpdateManager implements UpdateManager {
     /**
      *  Is an update available?
      *  Blocking.
+     *  An available update may still have a constraint or lack sources.
      *  @param maxWait max time to block
      *  @return new version or null if nothing newer is available
      */
@@ -244,7 +245,8 @@ public class ConsoleUpdateManager implements UpdateManager {
 
     /**
      *  Is an update available?
-     *  Non-blocking, returns result of last check or notification from an Updater
+     *  Non-blocking, returns result of last check or notification from an Updater.
+     *  An available update may still have a constraint or lack sources.
      *  @return new version or null if nothing newer is available
      */
     public String getUpdateAvailable(UpdateType type) {
@@ -253,7 +255,8 @@ public class ConsoleUpdateManager implements UpdateManager {
 
     /**
      *  Is an update available?
-     *  Non-blocking, returns result of last check or notification from an Updater
+     *  Non-blocking, returns result of last check or notification from an Updater.
+     *  An available update may still have a constraint or lack sources.
      *  @return new version or null if nothing newer is available
      */
     public String getUpdateAvailable(UpdateType type, String id) {
@@ -497,7 +500,6 @@ public class ConsoleUpdateManager implements UpdateManager {
                 _log.warn("Update already in progress for: " + type + ' ' + id);
             return false;
         }
-        List<URI> updateSources = null;
         UpdateItem ui = new UpdateItem(type, id);
         VersionAvailable va = _available.get(ui);
         if (va == null) {
@@ -748,6 +750,54 @@ public class ConsoleUpdateManager implements UpdateManager {
         return true;
     }
 
+    /**
+     *  A new version is available but cannot be downloaded or installed due to some constraint.
+     *  The manager should notify the user.
+     *  Called by the Checker, either after check() was called, or it found out on its own.
+     *
+     *  @param newsSource who told us
+     *  @param id plugin name for plugins, ignored otherwise
+     *  @param sourceMap Mapping of methods to sources
+     *  @param newVersion The new version available
+     *  @param message A translated message to be displayed to the user, non-null
+     *  @since 0.9.9
+     */
+    public void notifyVersionConstraint(UpdateTask task, URI newsSource,
+                                        UpdateType type, String id,
+                                        String newVersion, String message) {
+        UpdateItem ui = new UpdateItem(type, id);
+        Version old = _installed.get(ui);
+        VersionAvailable newVA = new VersionAvailable(newVersion, message);
+        if (_log.shouldLog(Log.INFO))
+            _log.info("notifyVersionConstraint " + ui + ' ' + newVA + " old: " + old);
+        if (old != null && old.compareTo(newVA) >= 0) {
+            if (_log.shouldLog(Log.WARN))
+                _log.warn(ui.toString() + ' ' + old + " already installed");
+            return;
+        }
+        old = _downloaded.get(ui);
+        if (old != null && old.compareTo(newVA) >= 0) {
+            if (_log.shouldLog(Log.WARN))
+                _log.warn(ui.toString() + ' ' + old + " already downloaded");
+            return;
+        }
+        VersionAvailable oldVA = _available.get(ui);
+        if (oldVA != null)  {
+            if (_log.shouldLog(Log.WARN))
+                _log.warn(ui.toString() + ' ' + oldVA + " already available");
+            if (oldVA.compareTo(newVA) >= 0)
+                return;
+            // don't replace an unconstrained version with a constrained one
+            if (oldVA.constraint == null)
+                return;
+            // replace constrained one
+        }
+        // Use the new VersionAvailable
+        if (_log.shouldLog(Log.INFO))
+            _log.info(ui.toString() + ' ' + newVA + " now available");
+        _available.put(ui, newVA);
+    }
+
     /**
      *  Called by the Updater after check() was called and all notifyVersionAvailable() callbacks are finished
      */
@@ -1005,6 +1055,18 @@ public class ConsoleUpdateManager implements UpdateManager {
         }
         return Collections.EMPTY_LIST;
     }
+    
+    /**
+     *  Is there a reason we can't download the update?
+     *  @return translated contraint or null
+     *  @since 0.9.9
+     */
+    public String getUpdateConstraint(UpdateType type, String id) {
+        VersionAvailable va = _available.get(new UpdateItem(type, id));
+        if (va != null)
+            return va.constraint;
+        return null;
+    }
 
     /**
      *
@@ -1118,6 +1180,14 @@ public class ConsoleUpdateManager implements UpdateManager {
         return Messages.getString(s, o, _context);
     }
 
+    /**
+     *  translate a string with parameters
+     *  @since 0.9.9
+     */
+    public String _(String s, Object o, Object o2) {
+        return Messages.getString(s, o, o2, _context);
+    }
+
     private void updateStatus(String s) {
         _status = s;
     }
@@ -1301,6 +1371,7 @@ public class ConsoleUpdateManager implements UpdateManager {
     private static class VersionAvailable extends Version {
         public final String minVersion;
         public final ConcurrentHashMap<UpdateMethod, List<URI>> sourceMap;
+        public volatile String constraint;
 
         /**
          * Puts the method and sources in the map. The map may be added to later.
@@ -1312,9 +1383,21 @@ public class ConsoleUpdateManager implements UpdateManager {
             sourceMap.put(method, updateSources);
         }
 
+        /**
+         * Available but can't be downloaded due to constraint.
+         *
+         */
+        public VersionAvailable(String version, String constraint) {
+            super(version);
+            minVersion = "";
+            sourceMap = new ConcurrentHashMap(4);
+            this.constraint = constraint;
+        }
+
         @Override
         public String toString() {
-            return "VersionAvailable \"" + version + "\" " + sourceMap;
+            return "VersionAvailable \"" + version + "\" " + sourceMap +
+                   (constraint != null ? (" \"" + constraint + '"') : "");
         }
     }
 
diff --git a/apps/routerconsole/java/src/net/i2p/router/update/NewsFetcher.java b/apps/routerconsole/java/src/net/i2p/router/update/NewsFetcher.java
index 61ae0354c..ba309d3de 100644
--- a/apps/routerconsole/java/src/net/i2p/router/update/NewsFetcher.java
+++ b/apps/routerconsole/java/src/net/i2p/router/update/NewsFetcher.java
@@ -31,6 +31,7 @@ import net.i2p.util.EepGet;
 import net.i2p.util.EepHead;
 import net.i2p.util.FileUtil;
 import net.i2p.util.Log;
+import net.i2p.util.VersionComparator;
 
 /**
  * Task to fetch updates to the news.xml, and to keep
@@ -60,10 +61,6 @@ class NewsFetcher extends UpdateRunner {
     @Override
     public UpdateType getType() { return NEWS; }
 
-    private boolean dontInstall() {
-        return NewsHelper.dontInstall(_context);
-    }
-
     @Override
     public void run() {
         _isRunning = true;
@@ -111,9 +108,12 @@ class NewsFetcher extends UpdateRunner {
     private static final String VERSION_PREFIX = "<i2p.release ";
     // all keys mapped to lower case by parseArgs()
     private static final String VERSION_KEY = "version";
+    // you have to be at least this version to update to the new version
     private static final String MIN_VERSION_KEY = "minversion";
+    private static final String MIN_JAVA_VERSION_KEY = "minjavaversion";
     private static final String SUD_KEY = "sudtorrent";
     private static final String SU2_KEY = "su2torrent";
+    // following are unused
     private static final String CLEARNET_SUD_KEY = "sudclearnet";
     private static final String CLEARNET_SU2_KEY = "su2clearnet";
     private static final String I2P_SUD_KEY = "sudi2p";
@@ -125,11 +125,6 @@ class NewsFetcher extends UpdateRunner {
      *  TODO: Check minVersion, use backup URLs specified
      */
     void checkForUpdates() {
-        // For now, don't even tell the manager about new versions if we can't install.
-        // If we do want the manager to know, we must hide the buttons in
-        // SummaryHelper.getUpdateStatus().
-        if (dontInstall())
-            return;
         FileInputStream in = null;
         try {
             in = new FileInputStream(_newsFile);
@@ -143,6 +138,37 @@ class NewsFetcher extends UpdateRunner {
                         if (_log.shouldLog(Log.DEBUG))
                             _log.debug("Found version: [" + ver + "]");
                         if (TrustedUpdate.needsUpdate(RouterVersion.VERSION, ver)) {
+                            if (NewsHelper.isUpdateDisabled(_context)) {
+                                String msg = _mgr._("In-network updates disabled. Check package manager.");
+                                _log.logAlways(Log.WARN, "Cannot update to version " + ver + ": " + msg);
+                                _mgr.notifyVersionConstraint(this, _currentURI, ROUTER_SIGNED, "", ver, msg);
+                                return;
+                            }
+                            if (NewsHelper.isBaseReadonly(_context)) {
+                                String msg = _mgr._("No write permission for I2P install directory.");
+                                _log.logAlways(Log.WARN, "Cannot update to version " + ver + ": " + msg);
+                                _mgr.notifyVersionConstraint(this, _currentURI, ROUTER_SIGNED, "", ver, msg);
+                                return;
+                            }
+                            String minRouter = args.get(MIN_VERSION_KEY);
+                            if (minRouter != null) {
+                                if (VersionComparator.comp(RouterVersion.VERSION, minRouter) < 0) {
+                                    String msg = _mgr._("You must first update to version {0}", minRouter);
+                                    _log.logAlways(Log.WARN, "Cannot update to version " + ver + ": " + msg);
+                                    _mgr.notifyVersionConstraint(this, _currentURI, ROUTER_SIGNED, "", ver, msg);
+                                    return;
+                                }
+                            }
+                            String minJava = args.get(MIN_JAVA_VERSION_KEY);
+                            if (minJava != null) {
+                                String ourJava = System.getProperty("java.version");
+                                if (VersionComparator.comp(ourJava, minJava) < 0) {
+                                    String msg = _mgr._("Requires Java version {0} but installed Java version is {1}", minJava, ourJava);
+                                    _log.logAlways(Log.WARN, "Cannot update to version " + ver + ": " + msg);
+                                    _mgr.notifyVersionConstraint(this, _currentURI, ROUTER_SIGNED, "", ver, msg);
+                                    return;
+                                }
+                            }
                             if (_log.shouldLog(Log.DEBUG))
                                 _log.debug("Our version is out of date, update!");
                             // TODO if minversion > our version, continue
diff --git a/apps/routerconsole/java/src/net/i2p/router/web/NewsHelper.java b/apps/routerconsole/java/src/net/i2p/router/web/NewsHelper.java
index c1fbf2b05..f04f1847b 100644
--- a/apps/routerconsole/java/src/net/i2p/router/web/NewsHelper.java
+++ b/apps/routerconsole/java/src/net/i2p/router/web/NewsHelper.java
@@ -74,6 +74,17 @@ public class NewsHelper extends ContentHelper {
         return mgr.getUpdateAvailable(ROUTER_SIGNED);
     }
 
+    /**
+     *  Translated message about new version available but constrained
+     *  @return null if none
+     *  @since 0.9.9
+     */
+    public static String updateConstraint() {
+        ConsoleUpdateManager mgr = ConsoleUpdateManager.getInstance();
+        if (mgr == null) return null;
+        return mgr.getUpdateConstraint(ROUTER_SIGNED, "");
+    }
+
     /**
      *  Already downloaded but not installed version
      *  @return null if none
@@ -259,9 +270,20 @@ public class NewsHelper extends ContentHelper {
      *  @since 0.9.4 moved from NewsFetcher
      */
     public static boolean dontInstall(RouterContext ctx) {
-        boolean disabled = ctx.getBooleanProperty(ConfigUpdateHandler.PROP_UPDATE_DISABLED);
-        if (disabled)
-            return true;
+        return isUpdateDisabled(ctx) || isBaseReadonly(ctx);
+    }
+    
+    /**
+     *  @since 0.9.9
+     */
+    public static boolean isUpdateDisabled(RouterContext ctx) {
+        return ctx.getBooleanProperty(ConfigUpdateHandler.PROP_UPDATE_DISABLED);
+    }
+    
+    /**
+     *  @since 0.9.9
+     */
+    public static boolean isBaseReadonly(RouterContext ctx) {
         File test = new File(ctx.getBaseDir(), "history.txt");
         boolean readonly = ((test.exists() && !test.canWrite()) || (!ctx.getBaseDir().canWrite()));
         return readonly;
diff --git a/apps/routerconsole/java/src/net/i2p/router/web/SummaryHelper.java b/apps/routerconsole/java/src/net/i2p/router/web/SummaryHelper.java
index 7d75790ae..9ad087a6d 100644
--- a/apps/routerconsole/java/src/net/i2p/router/web/SummaryHelper.java
+++ b/apps/routerconsole/java/src/net/i2p/router/web/SummaryHelper.java
@@ -678,7 +678,22 @@ public class SummaryHelper extends HelperBase {
             buf.append(' ').append(_("Version {0}", dver));
             buf.append("</b></h4>");
         }
-        if ((updateAvailable() || unsignedUpdateAvailable()) &&
+        boolean avail = updateAvailable();
+        boolean unsignedAvail = unsignedUpdateAvailable();
+        String constraint = avail ? NewsHelper.updateConstraint() : null;
+        if (avail && constraint != null &&
+            !NewsHelper.isUpdateInProgress() &&
+            !_context.router().gracefulShutdownInProgress()) {
+            if (needSpace)
+                buf.append("<hr>");
+            else
+                needSpace = true;
+            buf.append("<h4><b>").append(_("Update available")).append(":<br>");
+            buf.append(_("Version {0}", getUpdateVersion())).append("<br>");
+            buf.append(constraint).append("</h4>");
+            avail = false;
+        }
+        if ((avail || unsignedAvail) &&
             !NewsHelper.isUpdateInProgress() &&
             !_context.router().gracefulShutdownInProgress() &&
             _context.portMapper().getPort(PortMapper.SVC_HTTP_PROXY) > 0 &&  // assume using proxy for now
@@ -694,13 +709,13 @@ public class SummaryHelper extends HelperBase {
                 String uri = getRequestURI();
                 buf.append("<form action=\"").append(uri).append("\" method=\"POST\">\n");
                 buf.append("<input type=\"hidden\" name=\"updateNonce\" value=\"").append(nonce).append("\" >\n");
-                if (updateAvailable()) {
+                if (avail) {
                     buf.append("<button type=\"submit\" class=\"download\" name=\"updateAction\" value=\"signed\" >")
                        // Note to translators: parameter is a version, e.g. "0.8.4"
                        .append(_("Download {0} Update", getUpdateVersion()))
                        .append("</button><br>\n");
                 }
-                if (unsignedUpdateAvailable()) {
+                if (unsignedAvail) {
                     buf.append("<button type=\"submit\" class=\"download\" name=\"updateAction\" value=\"Unsigned\" >")
                        // Note to translators: parameter is a date and time, e.g. "02-Mar 20:34 UTC"
                        // <br> is optional, to help the browser make the lines even in the button
diff --git a/core/java/src/net/i2p/update/UpdateManager.java b/core/java/src/net/i2p/update/UpdateManager.java
index 06ecbeac6..bda8095f8 100644
--- a/core/java/src/net/i2p/update/UpdateManager.java
+++ b/core/java/src/net/i2p/update/UpdateManager.java
@@ -67,6 +67,22 @@ public interface UpdateManager {
                                           Map<UpdateMethod, List<URI>> sourceMap,
                                           String newVersion, String minVersion);
 
+    /**
+     *  A new version is available but cannot be downloaded or installed due to some constraint.
+     *  The manager should notify the user.
+     *  Called by the Checker, either after check() was called, or it found out on its own.
+     *
+     *  @param newsSource who told us
+     *  @param id plugin name for plugins, ignored otherwise
+     *  @param sourceMap Mapping of methods to sources
+     *  @param newVersion The new version available
+     *  @param message A translated message to be displayed to the user, non-null
+     *  @since 0.9.9
+     */
+    public void notifyVersionConstraint(UpdateTask task, URI newsSource,
+                                        UpdateType type, String id,
+                                        String newVersion, String message);
+
     /**
      *  Called by the Checker after check() was called and all notifyVersionAvailable() callbacks are finished
      *  @param newer notifyVersionAvailable was called