Add troubleshooting for Docker image on Fedora vs. Ubuntu

Author: szarnyasg

README.md

@@ -251,3 +251,4 @@ The graph schema is as follows:
 * When running the tests, they might throw a `java.net.UnknownHostException: your_hostname: your_hostname: Name or service not known` coming from `org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal`. The solution is to add an entry of your machine's hostname to the `/etc/hosts` file: `127.0.1.1 your_hostname`.
 * If you are using Docker and Spark runs out of space, make sure that Docker has enough space to store its containers. To move the location of the Docker containers to a larger disk, stop Docker, edit (or create) the `/etc/docker/daemon.json` file and add `{ "data-root": "/path/to/new/docker/data/dir" }`, then sync the old folder if needed, and restart Docker. (See [more detailed instructions](https://www.guguweb.com/2019/02/07/how-to-move-docker-data-directory-to-another-location-on-ubuntu/)).
 * If you are using a local Spark installation and run out of space in `/tmp` (`java.io.IOException: No space left on device`), set the `SPARK_LOCAL_DIRS` to point to a directory with enough free space.
+* The Docker image may throw the following error when generating factors `java.io.FileNotFoundException: /tmp/blockmgr-.../.../temp_shuffle_... (No file descriptors available)`. This error occurs on Fedora 36 host machines. Changing to an Ubuntu 22.04 host machine resolves the problem. Related issue: [#420](https://github.com/ldbc/ldbc_snb_datagen_spark/issues/420).