Pure-ftpd: first connection works, second connection fails

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Environment

SUSE Linux Enterprise Server 11 Service Pack 2

Situation

After launching pure-ftpd, the first FTP client session will work. The second (and thereafter) will be closed with a message such as:

421 Service not available, remote server has closed connection.

If pure-ftpd is restarted, the pattern will repeat.

Resolution

Edit /etc/pure-ftpd/pure-ftpd.conf and examine the "PassivePortRange" setting. It should appear as:

PassivePortRange minport:maxport

Where "minport" is the beginning of the passive port range, and "maxport" is the end. If these 2 numbers are the same, pure-ftpd will malfunction. The size of the range [(max minus min) plus 1] should be twice the size of the number of FTP clients that are to be supported. For example, a range of 30001:30100 is 100 in size and will support 50 clients.

Cause

Administrators are often finding that this range of ports has been set to "1024:1024", thus causing this behavior. That invalid setting comes from a malfunction in yast's FTP Server configuration tool (yast2-ftp-server).

To make sure yast doesn't misread this setting and replace it, it should have a colon between the numbers. This is a yast issue, as pure-ftpd.conf (on SLES) accepts either a colon or a space for this particular setting. Yast is not recognizing the space, and therefore replaces the entire line with a new one. The new line, as "corrected" by yast, is (ironically) invalid, because it starts and ends at the same port number.

A fix to yast is available in the package yast2-ftp-server, version 2.17.9-0.5.2, which is availabe in SLES 11 SP2 online updates as of December 2012. This will allow yast to recognize both the space and the colon (:), and the line will not be replaced. Even so, if this configuration line has already been written incorrectly, it will need to be corrected manually.

NOTE: The existance of the "yast2-ftp-server" module is relatively new, for SLES. It has not been included for long. In the experience and opinion of this TID author, this module still has potential issues and sometimes does undesirable things to the pure-ftpd.conf file; and continuing the previous method of editing the pure-ftpd.conf manually will lead to the most predictable results.

Additional Information

Disclaimer

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