Expanded installation instructions

doc/getting-started/install.md

@@ -113,6 +113,13 @@ export LD_LIBRARY_PATH="/usr/local/lib:$LD_LIBRARY_PATH"
 export PKG_CONFIG_PATH="/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH"
 ```
 
+For some distributions you will also need to configure the dynamic linker.  If
+the executable is linked with the right `libsodium.so` file (which you can
+check with `ldd`) but the process isn't (it dies with unknown symbol exception
+or can check with `pldd`) added a file which points to installation target of
+`libsodium` (in standard configuration it is `/usr/local/lib`) under
+`/etc/ld.so.conf` and run `ldconfig`.
+
 ##### Using the ported `c` code
 
 In order to avoid having to install the custom version, `cardano-crypto-praos`