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<H2><A NAME="SECTION00061000000000000000"></A><A NAME="clamd"></A>
<BR>
Clam daemon
</H2>
<code>clamd</code> is a multi-threaded daemon that uses <SPAN CLASS="textit">libclamav</SPAN>
to scan files for viruses. It may work in one or both modes listening on:
<UL>
<LI>Unix (local) socket
</LI>
<LI>TCP socket
</LI>
</UL>
The daemon is fully configurable via the <code>clamd.conf</code> file
<A NAME="tex2html22"
HREF="footnode.html#foot239"><SUP><SPAN CLASS="arabic">9</SPAN></SUP></A>. <code>clamd</code> recognizes the following commands:
<UL>
<LI><SPAN CLASS="textbf">PING</SPAN>
<BR>
Check the daemon's state (should reply with "PONG").
</LI>
<LI><SPAN CLASS="textbf">VERSION</SPAN>
<BR>
Print program and database versions.
</LI>
<LI><SPAN CLASS="textbf">RELOAD</SPAN>
<BR>
Reload the databases.
</LI>
<LI><SPAN CLASS="textbf">SHUTDOWN</SPAN>
<BR>
Perform a clean exit.
</LI>
<LI><SPAN CLASS="textbf">SCAN file/directory</SPAN>
<BR>
Scan file or directory (recursively) with archive support
enabled (a full path is required).
</LI>
<LI><SPAN CLASS="textbf">RAWSCAN file/directory</SPAN>
<BR>
Scan file or directory (recursively) with archive and special file
support disabled (a full path is required).
</LI>
<LI><SPAN CLASS="textbf">CONTSCAN file/directory</SPAN>
<BR>
Scan file or directory (recursively) with archive support
enabled and don't stop the scanning when a virus is found.
</LI>
<LI><SPAN CLASS="textbf">MULTISCAN file/directory</SPAN>
<BR>
Scan file in a standard way or scan directory (recursively) using
multiple threads (to make the scanning faster on SMP machines).
</LI>
<LI><SPAN CLASS="textbf">INSTREAM</SPAN>
<BR> <SPAN CLASS="textit">It is mandatory to prefix this command with <SPAN CLASS="textbf">n</SPAN> or
<SPAN CLASS="textbf">z</SPAN>.</SPAN>
<BR>
Scan a stream of data. The stream is sent to clamd in chunks,
after INSTREAM, on the same socket on which the command
was sent. This avoids the overhead of establishing new TCP
connections and problems with NAT. The format of the chunk is:
<code><length><data></code> where <code><length></code> is the size of the
following data in bytes expressed as a 4 byte unsigned integer in
network byte order and <code><data></code> is the actual chunk. Streaming
is terminated by sending a zero-length chunk. Note: do not exceed
StreamMaxLength as defined in clamd.conf, otherwise clamd will
reply with <SPAN CLASS="textit">INSTREAM size limit exceeded</SPAN> and close the
connection.
</LI>
<LI><SPAN CLASS="textbf">FILDES</SPAN>
<BR> <SPAN CLASS="textit">It is mandatory to newline terminate this command, or prefix
with <SPAN CLASS="textbf">n</SPAN> or <SPAN CLASS="textbf">z</SPAN>. This command only works on UNIX
domain sockets.</SPAN>
<BR>
Scan a file descriptor. After issuing a FILDES command a subsequent
rfc2292/bsd4.4 style packet (with at least one dummy character) is
sent to clamd carrying the file descriptor to be scanned inside the
ancillary data. Alternatively the file descriptor may be sent in
the same packet, including the extra character.
</LI>
<LI><SPAN CLASS="textbf">STATS</SPAN>
<BR> <SPAN CLASS="textit">It is mandatory to newline terminate this command, or prefix
with <SPAN CLASS="textbf">n</SPAN> or <SPAN CLASS="textbf">z</SPAN>, it is recommended to only use the
<SPAN CLASS="textbf">z</SPAN> prefix.</SPAN>
<BR>
On this command clamd provides statistics about the scan queue,
contents of scan queue, and memory usage. The exact reply format is
subject to changes in future releases.
</LI>
<LI><SPAN CLASS="textbf">IDSESSION, END</SPAN>
<BR> <SPAN CLASS="textit">It is mandatory to prefix this command with <SPAN CLASS="textbf">n</SPAN> or
<SPAN CLASS="textbf">z</SPAN>, also all commands inside <SPAN CLASS="textbf">IDSESSION</SPAN> must be
prefixed.</SPAN>
<BR>
Start/end a clamd session. Within a session multiple
SCAN, INSTREAM, FILDES, VERSION, STATS commands can be sent on the
same socket without opening new connections. Replies from clamd
will be in the form <code><id>: <response></code> where <code><id></code> is
the request number (in ASCII, starting from 1) and <code><response></code>
is the usual clamd reply. The reply lines have the same delimiter
as the corresponding command had. Clamd will process the commands
asynchronously, and reply as soon as it has finished processing.
Clamd requires clients to read all the replies it sent, before
sending more commands to prevent send() deadlocks. The recommended
way to implement a client that uses IDSESSION is with non-blocking
sockets, and a select()/poll() loop: whenever send would block,
sleep in select/poll until either you can write more data, or read
more replies. <SPAN CLASS="textit">Note that using non-blocking sockets without
the select/poll loop and alternating recv()/send() doesn't comply
with clamd's requirements.</SPAN> If clamd detects that a client has
deadlocked, it will close the connection. Note that clamd may
close an IDSESSION connection too if the client doesn't follow the
protocol's requirements.
</LI>
<LI><SPAN CLASS="textbf">STREAM</SPAN> (deprecated, use <SPAN CLASS="textbf">INSTREAM</SPAN> instead)
<BR>
Scan stream: clamd will return a new port number you should
connect to and send data to scan.
</LI>
</UL>
It's recommended to prefix clamd commands with the letter <SPAN CLASS="textbf">z</SPAN>
(eg. zSCAN) to indicate that the command will be delimited by a NULL
character and that clamd should continue reading command data until a NULL
character is read. The null delimiter assures that the complete command
and its entire argument will be processed as a single command. Alternatively
commands may be prefixed with the letter <SPAN CLASS="textbf">n</SPAN> (e.g. nSCAN) to use
a newline character as the delimiter. Clamd replies will honour the
requested terminator in turn. If clamd doesn't recognize the command, or
the command doesn't follow the requirements specified below, it will reply
with an error message, and close the connection.
Clamd can handle the following signals:
<UL>
<LI><SPAN CLASS="textbf">SIGTERM</SPAN> - perform a clean exit
</LI>
<LI><SPAN CLASS="textbf">SIGHUP</SPAN> - reopen the log file
</LI>
<LI><SPAN CLASS="textbf">SIGUSR2</SPAN> - reload the database
</LI>
</UL>
Clamd should not be started in the background using the shell operator
<code>&</code> or external tools. Instead, you should run and wait for clamd
to load the database and daemonize itself. After that, clamd is instantly
ready to accept connections and perform file scanning.
<P>
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<ADDRESS>
Tomasz Kojm
2010-05-19
</ADDRESS>
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