Hacker Linux Uncovered

10.8. Supplementary Information

I have not described all of the wu-ftp server's configuration file directives. There are too many of them; I have described only the most important ones.

You can obtain additional information about a particular configuration file by checking the man page for that file.

You can also read the wu-ftp server documentation in the /usr/share/doc/wu- ftpd -X.X.X directory (X.X.X is the version number of the server installed on your machine).

All changes specified in the configuration file become effective immediately. However, clients have to reconnect to the server to start working with the new settings.

The following are some useful FTP server administering commands:

• ftpd Starts the server with special parameters. There are many possible attributes; information concerning them can be obtained from the ftpd man page. I have never had to resort to using the command options because once the server has been properly configured it works steadily.

• ftprestart Restarts the FTP server.

• ftpshut Shuts down the server. For example, to update software, don't just pull the plug on the server; shut it down in an orderly fashion. Use this command with the following options:

  • -l n Do not accept any new connections less than n minutes before the shutdown. Specify a time sufficient for the clients to properly finish their server operations.

  • -d n Disconnect the connections n minutes before shutting down the FTP server. I recommend setting the disconnection immediately or 1 minute before the shut down.

  • time Specifies the shutdown time for the FTP server and is similar to the same parameter in the Linux shutdown command. You can shut down the server immediately by specifying the value of the time parameter as now ; however, I recommend using the +n option (where n is time in minutes until the shutdown) or specifying the exact time in the HHMM format.

• ftpcount Displays the number of connected FTP users. When there is something funny going on in my system, I always check whether there are FTP clients connect. If there are, the next thing I want to know who is connected.

• ftpwho Displays a list of the connected FTP clients and their corresponding accounts used to establish the connection. Sometimes, it takes only one look to determine the connection is being used by a bad guy for example, a user who is not to be supposed to be using FTP at this time is shown in the accounts connected list.

• ckconfig Checks the FTP server's configuration and displays a report for each wu-ftp server configuration file.