## ProFTPD and the ScoreboardFile

What is the Scoreboard
The `ScoreboardFile` is used by `proftpd` for tracking information for each current FTP session. It is necessary for things like `MaxClients`, `MaxClientsPerUser`, etc. The utility programs (`ftpwho`, `ftpcount`, `ftptop`) read the scoreboard and display its information.

Here's how `proftpd` handles its scoreboard: There is a default path that `proftpd` will use for writing its scoreboard (`var/proftpd/proftpd.scoreboard`). This default path depends on how you install proftpd (i.e. if you install from source and use the --prefix `configure` option, the default path will be adjusted to honor your --prefix). However, you can also explicitly tell the daemon what location to use for its scoreboard using the `ScoreboardFile` configuration directive in your `proftpd.conf`. When the daemon starts up, it looks to see if there is a scoreboard already there; if there isn't, it makes a new one.

The most common error encountered when opening the scoreboard is:

      unable to open scoreboard: No such file or directory

This usually means that `proftpd` is trying to open a `ScoreboardFile` in a directory that does not exist. Some packages fail to create the needed directory; this will result in the error message above. If you cannot find your `ScoreboardFile`, you should try explicitly configuring the path to the file to use in your `proftpd.conf`, using the `ScoreboardFile` configuration directive, and then obtaining debugging output from your `proftpd`, to see if the daemon ran into problems using that defined location.

Frequently Asked Questions
Question: Why doesn't `proftpd` create the needed directories, if they're not there, when opening the scoreboard?
Answer: The short answer is because that is the job of the system administrator, not the application. The long reason is that `proftpd` does not know the filesystem layout being used, and does not know what sort of permissions should be given to any directories it might need to create for its scoreboard.

Question: Can I copy my scoreboard from one server to another?
Answer: No. `ScoreboardFile`s cannot be copied from server to server; they are specific to that particular installation.

In the same fashion, you should not try to place the scoreboard on an NFS filesystem. First, attempting to share the scoreboard is not supported, and will only lead to trouble. Second, NFS does not support file locking, which `proftpd` requires for handling the scoreboard.

Question: Why do I see "scrubbing scoreboard" in my debugging output?
Answer: There is a bad habit among system administrators of using ``kill -9'` to kill a misbehaving process. Any process that is terminated this way, though, does not have a chance of properly shutting down. Administrators would use ``kill -9'` on some of `proftpd`'s session processes, which means that they would not be able to remove themselves from the scoreboard. `ftpwho` and `ftptop` would show sessions that no longer existed.

The chance of changing this bad habit in system administrators is slim, so `proftpd` was changed to check the scoreboard periodically. It will scan the entire scoreboard file, and for each scoreboard session listed, it asks the operating system if that session process is still alive. If the answer is no, the entry is removed from the scoreboard. This process is known as "scrubbing".

Question: Our site has many connections, and it looks like the logins/sessions are slow. Analysis shows that the session processes are all waiting/competing for the `ScoreboardFile`. What can be done to fix this?
Answer: One particular trick to use for this situation is to use `/dev/null`, e.g.:

      ScoreboardFile /dev/null

For one site which tried this configuration, `proftpd` was able to function without complaining about using `/dev/null` as the `ScoreboardFile`, the system load dropped dramatically, and the FTP sessions were no longer slow.

However, be aware that using this trick causes the following to NOT work:

- ftpwho
- ftptop
- `MaxClients`
- `MaxClientsPerClass`
- `MaxClientsPerHost`
- `MaxClientsPerUser`
- `MaxConnectionsPerHost`
- `MaxHostsPerUser`
- `MaxTransfersPerHost`
- `MaxTransfersPerUser`

$Date: 2008/12/10 18:57:19 $