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7 --><title>Log Files - Apache HTTP Server</title><link href="./style/css/manual-sbar-right-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - blue (font 100%)" /><link href="./style/css/manual-sbar-right-90pc.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - blue (font 90%)" /><link href="./style/css/manual-sbar-right-fix15.css" rel="stylesheet" media="all" type="text/css" title="right sidebar - blue (font fix 15)" /><link href="./style/css/manual-sbar-right-fix13.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - blue (font fix 13)" /><link href="./style/css/manual-sbar-right-100pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - black (font 100%)" /><link href="./style/css/manual-sbar-right-90pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - black (font 90%)" /><link href="./style/css/manual-sbar-right-fix15-b.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - black (font fix 15)" /><link href="./style/css/manual-sbar-right-fix13-b.css" rel="alternate stylesheet" media="all" type="text/css" title="right sidebar - black (font fix 13)" /><link href="./style/css/manual-sbar-left-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - blue (font 100%)" /><link href="./style/css/manual-sbar-left-90pc.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - blue (font 90%)" /><link href="./style/css/manual-sbar-left-fix15.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - blue (font fix 15)" /><link href="./style/css/manual-sbar-left-fix13.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - blue (font fix 13)" /><link href="./style/css/manual-sbar-left-100pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - black (font 100%)" /><link href="./style/css/manual-sbar-left-90pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - black (font 90%)" /><link href="./style/css/manual-sbar-left-fix15-b.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - black (font fix 15)" /><link href="./style/css/manual-sbar-left-fix13-b.css" rel="alternate stylesheet" media="all" type="text/css" title="left sidebar - black (font fix 13)" /><link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - blue (font 100%)" /><link href="./style/css/manual-loose-90pc.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - blue (font 90%)" /><link href="./style/css/manual-loose-fix15.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - blue (font fix 15)" /><link href="./style/css/manual-loose-fix13.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - blue (font fix 13)" /><link href="./style/css/manual-loose-100pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - black (font 100%)" /><link href="./style/css/manual-loose-90pc-b.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - black (font 90%)" /><link href="./style/css/manual-loose-fix15-b.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - black (font fix 15)" /><link href="./style/css/manual-loose-fix13-b.css" rel="alternate stylesheet" media="all" type="text/css" title="loose style - black (font fix 13)" /><link href="./images/favicon.ico" rel="shortcut icon" /></head><body id="manual-page"><div id="page-header"><p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p><p class="apache">Apache HTTP Server Version 2.0</p><img alt="" src="./images/feather.gif" /></div><div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div><div id="path"><a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Log Files</h1>
8 <p>In order to effectively manage a web server, it is necessary
9 to get feedback about the activity and performance of the
10 server as well as any problems that may be occuring. The Apache
11 HTTP Server provides very comprehensive and flexible logging
12 capabilities. This document describes how to configure its
13 logging capabilities, and how to understand what the logs
15 </div><div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#security">Security Warning</a></li><li><img alt="" src="./images/down.gif" /> <a href="#errorlog">Error Log</a></li><li><img alt="" src="./images/down.gif" /> <a href="#accesslog">Access Log</a></li><li><img alt="" src="./images/down.gif" /> <a href="#rotation">Rotation Logs</a></li><li><img alt="" src="./images/down.gif" /> <a href="#piped">Piped Logs</a></li><li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li><li><img alt="" src="./images/down.gif" /> <a href="#other">Other Log Files</a></li></ul></div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="security" id="security">Security Warning</a></h2>
18 <p>Anyone who can write to the directory where Apache is
19 writing a log file can almost certainly gain access to the uid
20 that the server is started as, which is normally root. Do
21 <em>NOT</em> give people write access to the directory the logs
22 are stored in without being aware of the consequences; see the
23 <a href="misc/security_tips.html">security tips</a> document
26 <p>In addition, log files may contain information supplied
27 directly by the client, without escaping. Therefore, it is
28 possible for malicious clients to insert control-characters in
29 the log files, so care must be taken in dealing with raw
31 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="errorlog" id="errorlog">Error Log</a></h2>
34 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td /><td><ul><li><code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code></li><li><code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code></li></ul></td></tr></table>
36 <p>The server error log, whose name and location is set by the
37 <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code> directive, is the
38 most important log file. This is the place where Apache httpd
39 will send diagnostic information and record any errors that it
40 encounters in processing requests. It is the first place to
41 look when a problem occurs with starting the server or with the
42 operation of the server, since it will often contain details of
43 what went wrong and how to fix it.</p>
45 <p>The error log is usually written to a file (typically
46 <code>error_log</code> on unix systems and
47 <code>error.log</code> on Windows and OS/2). On unix systems it
48 is also possible to have the server send errors to
49 <code>syslog</code> or <a href="#piped">pipe them to a
52 <p>The format of the error log is relatively free-form and
53 descriptive. But there is certain information that is contained
54 in most error log entries. For example, here is a typical
57 <div class="example"><p><code>
58 [Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1]
59 client denied by server configuration:
60 /export/home/live/ap/htdocs/test
63 <p>The first item in the log entry is the date and time of the
64 message. The second entry lists the severity of the error being
65 reported. The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code>
66 directive is used to control the types of errors that are sent
67 to the error log by restricting the severity level. The third
68 entry gives the IP address of the client that generated the
69 error. Beyond that is the message itself, which in this case
70 indicates that the server has been configured to deny the
71 client access. The server reports the file-system path (as
72 opposed to the web path) of the requested document.</p>
74 <p>A very wide variety of different messages can appear in the
75 error log. Most look similar to the example above. The error
76 log will also contain debugging output from CGI scripts. Any
77 information written to <code>stderr</code> by a CGI script will
78 be copied directly to the error log.</p>
80 <p>It is not possible to customize the error log by adding or
81 removing information. However, error log entries dealing with
82 particular requests have corresponding entries in the <a href="#accesslog">access log</a>. For example, the above example
83 entry corresponds to an access log entry with status code 403.
84 Since it is possible to customize the access log, you can
85 obtain more information about error conditions using that log
88 <p>During testing, it is often useful to continuously monitor
89 the error log for any problems. On unix systems, you can
90 accomplish this using:</p>
92 <div class="example"><p><code>
95 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="accesslog" id="accesslog">Access Log</a></h2>
98 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_setenvif.html">mod_setenvif</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code></li></ul></td></tr></table>
100 <p>The server access log records all requests processed by the
101 server. The location and content of the access log are
102 controlled by the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
103 directive. The <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code>
104 directive can be used to simplify the selection of
105 the contents of the logs. This section describes how to configure the server
106 to record information in the access log.</p>
108 <p>Of course, storing the information in the access log is only
109 the start of log management. The next step is to analyze this
110 information to produce useful statistics. Log analysis in
111 general is beyond the scope of this document, and not really
112 part of the job of the web server itself. For more information
113 about this topic, and for applications which perform log
114 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
115 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
118 <p>Various versions of Apache httpd have used other modules and
119 directives to control access logging, including
120 mod_log_referer, mod_log_agent, and the
121 <code>TransferLog</code> directive. The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive now subsumes
122 the functionality of all the older directives.</p>
124 <p>The format of the access log is highly configurable. The
125 format is specified using a <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> that
126 looks much like a C-style printf(1) format string. Some
127 examples are presented in the next sections. For a complete
128 list of the possible contents of the format string, see the <a href="mod/mod_log_config.html#formats">mod_log_config
129 documentation</a>.</p>
131 <h3><a name="common" id="common">Common Log Format</a></h3>
134 <p>A typical configuration for the access log might look as
137 <div class="example"><p><code>
138 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
139 CustomLog logs/access_log common
142 <p>This defines the <em>nickname</em> <code>common</code> and
143 associates it with a particular log format string. The format
144 string consists of percent directives, each of which tell the
145 server to log a particular piece of information. Literal
146 characters may also be placed in the format string and will be
147 copied directly into the log output. The quote character
148 (<code>"</code>) must be escaped by placing a back-slash before
149 it to prevent it from being interpreted as the end of the
150 format string. The format string may also contain the special
151 control characters "<code>\n</code>" for new-line and
152 "<code>\t</code>" for tab.</p>
154 <p>The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
155 directive sets up a new log file using the defined
156 <em>nickname</em>. The filename for the access log is relative to
157 the <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> unless it
158 begins with a slash.</p>
160 <p>The above configuration will write log entries in a format
161 known as the Common Log Format (CLF). This standard format can
162 be produced by many different web servers and read by many log
163 analysis programs. The log file entries produced in CLF will
164 look something like this:</p>
166 <div class="example"><p><code>
167 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
168 /apache_pb.gif HTTP/1.0" 200 2326
171 <p>Each part of this log entry is described below.</p>
174 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
176 <dd>This is the IP address of the client (remote host) which
177 made the request to the server. If <code class="directive"><a href="./mod/core.html#hostnamelookups">HostnameLookups</a></code> is
178 set to <code>On</code>, then the server will try to determine
179 the hostname and log it in place of the IP address. However,
180 this configuration is not recommended since it can
181 significantly slow the server. Instead, it is best to use a
182 log post-processor such as <a href="programs/logresolve.html">logresolve</a> to determine
183 the hostnames. The IP address reported here is not
184 necessarily the address of the machine at which the user is
185 sitting. If a proxy server exists between the user and the
186 server, this address will be the address of the proxy, rather
187 than the originating machine.</dd>
189 <dt><code>-</code> (<code>%l</code>)</dt>
191 <dd>The "hyphen" in the output indicates that the requested
192 piece of information is not available. In this case, the
193 information that is not available is the RFC 1413 identity of
194 the client determined by <code>identd</code> on the clients
195 machine. This information is highly unreliable and should
196 almost never be used except on tightly controlled internal
197 networks. Apache httpd will not even attempt to determine
198 this information unless <code class="directive"><a href="./mod/core.html#identitycheck">IdentityCheck</a></code> is set
199 to <code>On</code>.</dd>
201 <dt><code>frank</code> (<code>%u</code>)</dt>
203 <dd>This is the userid of the person requesting the document
204 as determined by HTTP authentication. The same value is
205 typically provided to CGI scripts in the
206 <code>REMOTE_USER</code> environment variable. If the status
207 code for the request (see below) is 401, then this value
208 should not be trusted because the user is not yet
209 authenticated. If the document is not password protected,
210 this entry will be "<code>-</code>" just like the previous
213 <dt><code>[10/Oct/2000:13:55:36 -0700]</code>
214 (<code>%t</code>)</dt>
217 The time that the server finished processing the request.
221 <code>[day/month/year:hour:minute:second zone]<br />
223 month = 3*letter<br />
226 minute = 2*digit<br />
227 second = 2*digit<br />
228 zone = (`+' | `-') 4*digit</code>
230 It is possible to have the time displayed in another format
231 by specifying <code>%{format}t</code> in the log format
232 string, where <code>format</code> is as in
233 <code>strftime(3)</code> from the C standard library.
236 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
237 (<code>\"%r\"</code>)</dt>
239 <dd>The request line from the client is given in double
240 quotes. The request line contains a great deal of useful
241 information. First, the method used by the client is
242 <code>GET</code>. Second, the client requested the resource
243 <code>/apache_pb.gif</code>, and third, the client used the
244 protocol <code>HTTP/1.0</code>. It is also possible to log
245 one or more parts of the request line independently. For
246 example, the format string "<code>%m %U%q %H</code>" will log
247 the method, path, query-string, and protocol, resulting in
248 exactly the same output as "<code>%r</code>".</dd>
250 <dt><code>200</code> (<code>%>s</code>)</dt>
252 <dd>This is the status code that the server sends back to the
253 client. This information is very valuable, because it reveals
254 whether the request resulted in a successful response (codes
255 beginning in 2), a redirection (codes beginning in 3), an
256 error caused by the client (codes beginning in 4), or an
257 error in the server (codes beginning in 5). The full list of
258 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP
259 specification</a> (RFC2616 section 10).</dd>
261 <dt><code>2326</code> (<code>%b</code>)</dt>
263 <dd>The last entry indicates the size of the object returned
264 to the client, not including the response headers. If no
265 content was returned to the client, this value will be
266 "<code>-</code>". To log "<code>0</code>" for no content, use
267 <code>%B</code> instead.</dd>
271 <h3><a name="combined" id="combined">Combined Log Format</a></h3>
274 <p>Another commonly used format string is called the Combined
275 Log Format. It can be used as follows.</p>
277 <div class="example"><p><code>
278 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
279 \"%{User-agent}i\"" combined<br />
280 CustomLog log/acces_log combined
283 <p>This format is exactly the same as the Common Log Format,
284 with the addition of two more fields. Each of the additional
285 fields uses the percent-directive
286 <code>%{<em>header</em>}i</code>, where <em>header</em> can be
287 any HTTP request header. The access log under this format will
290 <div class="example"><p><code>
291 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
292 /apache_pb.gif HTTP/1.0" 200 2326
293 "http://www.example.com/start.html" "Mozilla/4.08 [en]
297 <p>The additional fields are:</p>
300 <dt><code>"http://www.example.com/start.html"</code>
301 (<code>\"%{Referer}i\"</code>)</dt>
303 <dd>The "Referer" (sic) HTTP request header. This gives the
304 site that the client reports having been referred from. (This
305 should be the page that links to or includes
306 <code>/apache_pb.gif</code>).</dd>
308 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code>
309 (<code>\"%{User-agent}i\"</code>)</dt>
311 <dd>The User-Agent HTTP request header. This is the
312 identifying information that the client browser reports about
317 <h3><a name="multiple" id="multiple">Multiple Access Logs</a></h3>
320 <p>Multiple access logs can be created simply by specifying
321 multiple <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
322 directives in the configuration
323 file. For example, the following directives will create three
324 access logs. The first contains the basic CLF information,
325 while the second and third contain referer and browser
326 information. The last two <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> lines show how
327 to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p>
329 <div class="example"><p><code>
330 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
331 CustomLog logs/access_log common<br />
332 CustomLog logs/referer_log "%{Referer}i -> %U"<br />
333 CustomLog logs/agent_log "%{User-agent}i"
336 <p>This example also shows that it is not necessary to define a
337 nickname with the <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> directive. Instead,
338 the log format can be specified directly in the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive.</p>
341 <h3><a name="conditional" id="conditional">Conditional Logs</a></h3>
344 <p>There are times when it is convenient to exclude certain
345 entries from the access logs based on characteristics of the
346 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
347 environment variable must be set to indicate that the request
348 meets certain conditions. This is usually accomplished with
349 <code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>. Then the
350 <code>env=</code> clause of the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive is used to
351 include or exclude requests where the environment variable is
352 set. Some examples:</p>
354 <div class="example"><p><code>
355 # Mark requests from the loop-back interface<br />
356 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br />
357 # Mark requests for the robots.txt file<br />
358 SetEnvIf Request_URI "^/robots\.txt$" dontlog<br />
359 # Log what remains<br />
360 CustomLog logs/access_log common env=!dontlog
363 <p>As another example, consider logging requests from
364 english-speakers to one log file, and non-english speakers to a
365 different log file.</p>
367 <div class="example"><p><code>
368 SetEnvIf Accept-Language "en" english<br />
369 CustomLog logs/english_log common env=english<br />
370 CustomLog logs/non_english_log common env=!english
373 <p>Although we have just shown that conditional logging is very
374 powerful and flexibly, it is not the only way to control the
375 contents of the logs. Log files are more useful when they
376 contain a complete record of server activity. It is often
377 easier to simply post-process the log files to remove requests
378 that you do not want to consider.</p>
380 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="rotation" id="rotation">Rotation Logs</a></h2>
383 <p>On even a moderately busy server, the quantity of
384 information stored in the log files is very large. The access
385 log file typically grows 1 MB or more per 10,000 requests. It
386 will consequently be necessary to periodically rotate the log
387 files by moving or deleting the existing logs. This cannot be
388 done while the server is running, because Apache will continue
389 writing to the old log file as long as it holds the file open.
390 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
391 moved or deleted so that it will open new log files.</p>
393 <p>By using a <em>graceful</em> restart, the server can be
394 instructed to open new log files without losing any existing or
395 pending connections from clients. However, in order to
396 accomplish this, the server must continue to write to the old
397 log files while it finishes serving old requests. It is
398 therefore necessary to wait for some time after the restart
399 before doing any processing on the log files. A typical
400 scenario that simply rotates the logs and compresses the old
401 logs to save space is:</p>
403 <div class="example"><p><code>
404 mv access_log access_log.old<br />
405 mv error_log error_log.old<br />
406 apachectl graceful<br />
408 gzip access_log.old error_log.old
411 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
413 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="piped" id="piped">Piped Logs</a></h2>
416 <p>Apache httpd is capable of writing error and access log
417 files through a pipe to another process, rather than directly
418 to a file. This capability dramatically increases the
419 flexibility of logging, without adding code to the main server.
420 In order to write logs to a pipe, simply replace the filename
421 with the pipe character "<code>|</code>", followed by the name
422 of the executable which should accept log entries on its
423 standard input. Apache will start the piped-log process when
424 the server starts, and will restart it if it crashes while the
425 server is running. (This last feature is why we can refer to
426 this technique as "reliable piped logging".)</p>
428 <p>Piped log processes are spawned by the parent Apache httpd
429 process, and inherit the userid of that process. This means
430 that piped log programs usually run as root. It is therefore
431 very important to keep the programs simple and secure.</p>
433 <p>Some simple examples using piped logs:</p>
435 <div class="example"><p><code>
436 # compressed logs<br />
437 CustomLog "|/usr/bin/gzip -c >>
438 /var/log/access_log.gz" common<br />
439 # almost-real-time name resolution<br />
440 CustomLog "|/usr/local/apache/bin/logresolve >>
441 /var/log/access_log" common
444 <p>Notice that quotes are used to enclose the entire command
445 that will be called for the pipe. Although these examples are
446 for the access log, the same technique can be used for the
449 <p>One important use of piped logs is to allow log rotation
450 without having to restart the server. The Apache HTTP Server
451 includes a simple program called <a href="programs/rotatelogs.html">rotatelogs</a> for this
452 purpose. For example, to rotate the logs every 24 hours, you
455 <div class="example"><p><code>
456 CustomLog "|/usr/local/apache/bin/rotatelogs
457 /var/log/access_log 86400" common
460 <p>A similar, but much more flexible log rotation program
461 called <a href="http://www.cronolog.org/">cronolog</a>
462 is available at an external site.</p>
464 <p>As with conditional logging, piped logs are a very powerful
465 tool, but they should not be used where a simpler solution like
466 off-line post-processing is available.</p>
467 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2>
470 <p>When running a server with many <a href="vhosts/">virtual
471 hosts</a>, there are several options for dealing with log
472 files. First, it is possible to use logs exactly as in a
473 single-host server. Simply by placing the logging directives
474 outside the <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code> sections in the
475 main server context, it is possible to log all requests in the
476 same access log and error log. This technique does not allow
477 for easy collection of statistics on individual virtual
480 <p>If <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
481 or <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code>
482 directives are placed inside a
483 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
484 section, all requests or errors for that virtual host will be
485 logged only to the specified file. Any virtual host which does
486 not have logging directives will still have its requests sent
487 to the main server logs. This technique is very useful for a
488 small number of virtual hosts, but if the number of hosts is
489 very large, it can be complicated to manage. In addition, it
490 can often create problems with <a href="vhosts/fd-limits.html">insufficient file
493 <p>For the access log, there is a very good compromise. By
494 adding information on the virtual host to the log format
495 string, it is possible to log all hosts to the same log, and
496 later split the log into individual files. For example,
497 consider the following directives.</p>
499 <div class="example"><p><code>
500 LogFormat "%v %l %u %t \"%r\" %>s %b"
502 CustomLog logs/access_log comonvhost
505 <p>The <code>%v</code> is used to log the name of the virtual
506 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
507 post-process the access log in order to split it into one file
508 per virtual host.</p>
509 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="other" id="other">Other Log Files</a></h2>
512 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlogbuffer">ScriptLogBuffer</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptloglength">ScriptLogLength</a></code></li></ul></td></tr></table>
514 <h3><a name="pidfile" id="pidfile">PID File</a></h3>
517 <p>On startup, Apache httpd saves the process id of the parent
518 httpd process to the file <code>logs/httpd.pid</code>. This
519 filename can be changed with the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> directive. The
520 process-id is for use by the administrator in restarting and
521 terminating the daemon by sending signals to the parent
522 process; on Windows, use the -k command line option instead.
523 For more information see the <a href="stopping.html">Stopping
524 and Restarting</a> page.</p>
527 <h3><a name="scriptlog" id="scriptlog">Script Log</a></h3>
530 <p>In order to aid in debugging, the
531 <code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code> directive
532 allows you to record the input to and output from CGI scripts.
533 This should only be used in testing - not for live servers.
534 More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p>
537 <h3><a name="rewritelog" id="rewritelog">Rewrite Log</a></h3>
540 <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost
541 always necessary to use the <code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code> to help
542 in debugging. This log file produces a detailed analysis of how
543 the rewriting engine transforms requests. The level of detail
544 is controlled by the <code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code> directive.</p>
546 </div></div><div id="footer"><p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p><p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p></div></body></html>
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