Logging the activity of the server is an integral part of effective server administration. ProFTPD provides several different and flexing logging mechanisms. When examining the different logging mechanisms, have in mind the intended use of the logged data, the volume, any post-processing that may need to be done, etc. Log files are more useful when they contain a complete record of server activity. It is often easier to simply post-process the log files to remove requests that you do not want to consider.
Anyone who can write to the directory where ProFTPD is writing a log file can almost certainly gain access to the UID that the server is started under, which is normally
root. Do not give people write access to the
directory where the logs are stored without being aware of the consequences:
if the logs directory is writable (by a non-
root user), someone
could replace a log file with a symlink to some other system file, and then
root might overwrite that file with arbitrary data. If the log
files themselves are writable (by a non-
root user), then someone
may be able to overwrite the log itself with bogus data.
When opening log files,
proftpd will by default log a warning if
the file being opened for logging is in a directory that does not exist, or
is world-writable. The log file will not be written in world-writable
directories; there are no exceptions. (If you have configured log files in
proftpd.conf that are not appearing, check for the warnings
about world-writable directories.) The
proftpd process will also,
by default, log a warning if the file given is a symlink; this symlink check
can be configured via the
In addition, log files may contain information supplied directly by the client, without escaping. Therefore, it is possible for malicious clients to insert control-characters in the log files, so care must be taken in dealing with raw logs.
proftpd will log via
daemon facility (
auth for some logging),
at various levels:
debug (debugging is done at this syslog
level). The location of the server's log files in this case is determined by
There are three main types of logs that a
proftpd daemon can
TransferLog is the most common log kept, recording file
transfers. Its format is described in the
xferlog(5) man page,
also available here
If the site administrator wants to have
proftpd log its
messages to a file rather than going through
SystemLog configuration directive is the one to use. There
is only one such file kept for the entire daemon. See the
ServerLog directive for keeping a similar log on a per-vhost basis.
The ExtendedLog directive is used to create log files of a very
flexible and configurable format, and to have granular control over what is
logged, and when. The format of an
ExtendedLog is described
using the LogFormat directive. Multiple
be configured, each with a different format.
There are a variety of log analyzers available; these are just a few:
On even a moderately busy server, the quantity of information stored in the log files is very large. It will consequently be necessary to periodically rotate the log files by moving or deleting the existing logs. This cannot be done while the server is running, because the daemon will continue writing to the old log file as long as it holds the file open. Instead, the server must be restarted after the log files are moved or deleted so that it will open new log files.
Another way to perform log rotation is using FIFOs as discussed in the next section.
FIFOs (a.k.a. named pipes)
ProFTPD is capable of writing log files to FIFOs, from which another process can read. Use of this capability dramatically increases the flexibility of logging, without adding code to the main server. In order to write logs to a pipe, simply create the FIFO at the desired path (
man mkfifo(1)), and use that path in the logging configuration
One important use of piped logs is to allow log rotation without having to restart the server. One such popular flexible log rotation program is cronolog; however, at present cronolog requires a small patch to enable it to read from a FIFO (by default, cronolog reads data from stdin). Please contact the author of this article for details concerning the patch.
Here's an example of FIFO-based logging script, based on one posted by Michael Renner:
#!/usr/bin/perl use strict; use File::Basename qw(basename); use Sys::Syslog qw(:DEFAULT setlogsock); my $program = basename($0); my $fifo = '/var/log/proftpd-log.fifo'; my $syslog_facility = 'daemon'; my $syslog_level = 'info'; open(FIFO, "< $fifo") or die "$program: unable to open $fifo: $!\n"; setlogsock 'unix'; openlog($program, 'pid', $syslog_facility); syslog($syslog_level, $_) while (More complex filtering can be added to such scripts.
); closelog(); close(FIFO); exit 0;
If using FIFOs, there are some caveats to keep in mind. If you use in
init.d script to start
standalone daemons, you can
add commands to start the FIFO logging programs first, before the daemon.
inetd-run servers, consider wrapping up the necessary
commands for starting a FIFO reader and the server into a simple shell
script, or simply run the FIFO-reading program from an
script, and save the overhead of starting that process, in addition to the
proftpd process, for each FTP session.
FIFO-based log readers are a very powerful tool, but they should not be used where a simpler solution like off-line post-processing is available.
mod_sql module also enables some powerful and complex
proftpd saves the process ID of the parent daemon
process to the file
var/proftpd/proftpd.pid. This filename can be
changed with the PidFile directive. The process ID (aka PID) is for
use by the administrator in restarting and terminating the daemon by sending
signals to the parent process. For more information see the
stopping and starting page.
The last type of "logging" is done via the scoreboard file. The scoreboard is binary-formatted file the server uses to store information about each session; it is this file that is read by
ftpcount. The location for the
scoreboard file is determined by the