+### I see the error: "ERROR: mmap (remap) failed"
+
+This may be a simple out-of-memory error. Try reducing the memory used
+for `--osm2pgsql-cache`. Also make sure that overcommitting memory is
+allowed: `cat /proc/sys/vm/overcommit_memory` should print 0 or 1.
+
+If you are using a flatnode file, then it may also be that the underlying
+filesystem does not fully support 'mmap'. A notable candidate is virtualbox's
+vboxfs.
+
+### I see the error: "clang: Command not found" on CentOS
+
+On CentOS 7 users reported `/opt/rh/llvm-toolset-7/root/usr/bin/clang: Command not found`.
+Double-check clang is installed. Instead of `make` try running `make CLANG=true`.
+
+### nominatim UPDATE failed: ERROR: buffer 179261 is not owned by resource owner Portal
+
+Several users [reported this](https://github.com/openstreetmap/Nominatim/issues/1168) during the initial import of the database. It's
+something PostgreSQL internal Nominatim doesn't control. And PostgreSQL forums
+suggest it's threading related but definitely some kind of crash of a process.
+Users reported either rebooting the server, different hardware or just trying
+the import again worked.