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ProFTPD module mod_deflate
ProFTPD module mod_deflate
The mod_deflate module is designed to provide support for
MODE Z commands, which allows FTP clients and servers to
compress data for transfer.
This module is contained in the mod_deflate.c file for
ProFTPD 1.3.x, and is not compiled by default. Installation instructions
are discussed here. Detailed documentation on
mod_deflate usage can be found here.
The most current version of mod_deflate can be found at:
http://www.castaglia.org/proftpd/
Author
Please contact TJ Saunders <tj at castaglia.org> with any
questions, concerns, or suggestions regarding this module.
Directives
Syntax: DeflateEngine on|off
Default: off
Context: server config, <VirtualHost>, <Global>
Module: mod_deflate
Compatibility: 1.3.0rc1 and later
The DeflateEngine directive enables or disables the
mod_deflate compression functionality. If set to on,
then mod_deflate will advertise support for MODE Z
compression via the FEAT command, and handle MODE Z
requests appropriately.
Syntax: DeflateLog path|"none"
Default: None
Context: server config, <VirtualHost>, <Global>
Module: mod_deflate
Compatibility: 1.3.0rc1 and later
The DeflateLog directive is used to specify a log file for
mod_deflate reporting and debugging. The path parameter
must be the full path to the file to use for logging. Note that this path must
not be to a world-writable directory and, unless
AllowLogSymlinks is explicitly set to on
(generally a bad idea), the path must not be a symbolic link.
If path is "none", no logging will be done at all.
The mod_deflate module is distributed with ProFTPD. Follow the
usual steps for using third-party modules in ProFTPD:
$ ./configure --with-modules=mod_deflate
To build mod_deflate as a DSO module:
$ ./configure --enable-dso --with-shared=mod_deflate
Then follow the usual steps:
$ make
$ make install
For those with an existing ProFTPD installation, you can use the
prxs tool to add mod_deflate, as a DSO module, to
your existing server:
$ prxs -c -i -d mod_deflate.c
Example mod_deflate configuration:
<IfModule mod_deflate.c>
DeflateEngine on
DeflateLog /var/log/proftpd/deflate.log
</IfModule>
Sites that run proftpd 1.3.0 should disable sendfile use
when using mod_deflate, as the two features do not interoperate
well:
<IfModule mod_deflate.c>
DeflateEngine on
DeflateLog /var/log/proftpd/deflate.log
UseSendfile off
</IfModule>
Logging
The mod_deflate module supports different forms of logging. The
main module logging is done via the DeflateLog directive.
For debugging purposes, the module also uses trace logging, via the module-specific log channels:
Thus for trace logging, to aid in debugging, you would use the following in
your proftpd.conf:
TraceLog /path/to/ftpd/trace.log
Trace deflate:20
This trace logging can generate large files; it is intended for debugging use
only, and should be removed from any production configuration.
Frequently Asked Questions
Question: I'm uploading a file using MODE Z,
but the upload always fails. In the DeflateLog, I see:
error inflating data: [-3] Data error
What is going wrong? It is a mod_deflate bug?
Answer: The most common cause of this error is when
the client is trying to upload a binary file (e.g. PDF, MPG, etc)
in ASCII mode.
If MODE Z is not used in cases like this, the upload succeeds,
but the uploaded file on the server is corrupted. When MODE Z
is in effect, the corruption (translation of newlines inappropriately) is
detected earlier (since mod_deflate can't uncompress the
compressed data properly, hence the report of a "Data error"), and the
upload fails.
The solution is make sure that the client uploads (and downloads) non-ASCII
files as binary files, not as ASCII files.
© Copyright 2006-2017 TJ Saunders
All Rights Reserved
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