Ask for a different disk if not found

lib/modules/partition.nix

@@ -161,8 +161,26 @@
                 if osDisk && config.devicePath == null then ''
                   ${diskSelector}
                 ''
+                else ''
+                  local ${diskVarName}=${config.devicePath}
+                  ${if osDisk then ''
+                    . ${./../../../scripts/Common/Scripts/is-truthy.sh}
+                    if [ ! -b ${diskVar} ]; then
+                      function fallback() {
+                        echo "Couldn't find the specified disk \"${diskVar}\"."
+                        echo "Do you want to install the OS on another disk?"
+                        local answer
+                        read answer
+                        if isTruthy "$answer"; then
+                          ${diskSelector}
                         else
-                  "local ${diskVarName}=${config.devicePath}"}
+                          exit 1
+                        fi
+                      }
+                      fallback;
+                    fi
+                  '' else ""}
+                ''}
 
               ${if (!config.wipe) then cleanup else ""}