+h3. Legacy container logging system has been removed
+
+The following configuration keys are no longer supported. Remove them from your @/etc/arvados/config.yml@ file to avoid warnings when services start up.
+* @Containers.Logging.LimitLogBytesPerJob@
+* @Containers.Logging.LogBytesPerEvent@
+* @Containers.Logging.LogPartialLineThrottlePeriod@
+* @Containers.Logging.LogSecondsBetweenEvents@
+* @Containers.Logging.LogThrottleBytes@
+* @Containers.Logging.LogThrottleLines@
+* @Containers.Logging.LogThrottlePeriod@
+* @Containers.Logging.MaxAge@
+* @Containers.Logging.SweepInterval@
+
+Any container logging content remaining in the database from the legacy system will be deleted.
+
+h3. Virtual environments inside distribution Python packages have moved
+
+The distribution packages that we publish for Python packages include an entire virtualenv with all required libraries. In Arvados 3.0 these virtualenvs have moved from @/usr/share/python3/dist/PACKAGE_NAME@ to @/usr/lib/PACKAGE_NAME@ to prevent conflicts with distribution packages and better conform to filesystem standards.
+
+If you only run the executables installed by these packages, you don't need to change anything. Those are still installed under @/usr/bin@ and will use the new location when you upgrade. If you have written your own scripts or tools that rely on these virtualenvs, you may need to update those with the new location. For example, if you have a shell script that activates the virtualenv by running:
+
+<pre><code class="shell">source /usr/share/python3/dist/python3-arvados-python-client/bin/activate</code></pre>
+
+You must update it to:
+
+<notextile>
+<pre><code class="shell">source <span class="userinput">/usr/lib/python3-arvados-python-client</span>/bin/activate</code></pre>
+</notextile>
+
+If you have a Python script with this shebang line:
+
+<pre><code class="shell">#!/usr/share/python3/dist/python3-arvados-python-client/bin/python</code></pre>
+
+You must update it to:
+
+<notextile>
+<pre><code class="shell">#!<span class="userinput">/usr/lib/python3-arvados-python-client</span>/bin/python</code></pre>
+</notextile>
+