1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>Log Files - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body id="manual-page"><div id="page-header"> 17<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 18<p class="apache">Apache HTTP Server Version 2.2</p> 19<img alt="" src="/images/feather.gif" /></div> 20<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 21<div id="path"> 22<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.2</a></div><div id="page-content"><div id="preamble"><h1>Log Files</h1> 23<div class="toplang"> 24<p><span>Available Languages: </span><a href="/en/logs.html" title="English"> en </a> | 25<a href="/fr/logs.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 26<a href="/ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 27<a href="/ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | 28<a href="/tr/logs.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 29</div> 30 31 <p>In order to effectively manage a web server, it is necessary 32 to get feedback about the activity and performance of the 33 server as well as any problems that may be occurring. The Apache 34 HTTP Server provides very comprehensive and flexible logging 35 capabilities. This document describes how to configure its 36 logging capabilities, and how to understand what the logs 37 contain.</p> 38 </div> 39<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#security">Security Warning</a></li> 40<li><img alt="" src="/images/down.gif" /> <a href="#errorlog">Error Log</a></li> 41<li><img alt="" src="/images/down.gif" /> <a href="#accesslog">Access Log</a></li> 42<li><img alt="" src="/images/down.gif" /> <a href="#rotation">Log Rotation</a></li> 43<li><img alt="" src="/images/down.gif" /> <a href="#piped">Piped Logs</a></li> 44<li><img alt="" src="/images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li> 45<li><img alt="" src="/images/down.gif" /> <a href="#other">Other Log Files</a></li> 46</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 47<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 48<div class="section"> 49<h2><a name="security" id="security">Security Warning</a></h2> 50 51 52 <p>Anyone who can write to the directory where Apache is 53 writing a log file can almost certainly gain access to the uid 54 that the server is started as, which is normally root. Do 55 <em>NOT</em> give people write access to the directory the logs 56 are stored in without being aware of the consequences; see the 57 <a href="misc/security_tips.html">security tips</a> document 58 for details.</p> 59 60 <p>In addition, log files may contain information supplied 61 directly by the client, without escaping. Therefore, it is 62 possible for malicious clients to insert control-characters in 63 the log files, so care must be taken in dealing with raw 64 logs.</p> 65 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 66<div class="section"> 67<h2><a name="errorlog" id="errorlog">Error Log</a></h2> 68 69 70 <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> 71 72 <p>The server error log, whose name and location is set by the 73 <code class="directive"><a href="/mod/core.html#errorlog">ErrorLog</a></code> directive, is the 74 most important log file. This is the place where Apache httpd 75 will send diagnostic information and record any errors that it 76 encounters in processing requests. It is the first place to 77 look when a problem occurs with starting the server or with the 78 operation of the server, since it will often contain details of 79 what went wrong and how to fix it.</p> 80 81 <p>The error log is usually written to a file (typically 82 <code>error_log</code> on Unix systems and 83 <code>error.log</code> on Windows and OS/2). On Unix systems it 84 is also possible to have the server send errors to 85 <code>syslog</code> or <a href="#piped">pipe them to a 86 program</a>.</p> 87 88 <p>The format of the error log is relatively free-form and 89 descriptive. But there is certain information that is contained 90 in most error log entries. For example, here is a typical 91 message.</p> 92 93 <div class="example"><p><code> 94 [Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1] 95 client denied by server configuration: 96 /export/home/live/ap/htdocs/test 97 </code></p></div> 98 99 <p>The first item in the log entry is the date and time of the 100 message. The second item lists the severity of the error being 101 reported. The <code class="directive"><a href="/mod/core.html#loglevel">LogLevel</a></code> 102 directive is used to control the types of errors that are sent 103 to the error log by restricting the severity level. The third 104 item gives the IP address of the client that generated the 105 error. Beyond that is the message itself, which in this case 106 indicates that the server has been configured to deny the 107 client access. The server reports the file-system path (as 108 opposed to the web path) of the requested document.</p> 109 110 <p>A very wide variety of different messages can appear in the 111 error log. Most look similar to the example above. The error 112 log will also contain debugging output from CGI scripts. Any 113 information written to <code>stderr</code> by a CGI script will 114 be copied directly to the error log.</p> 115 116 <p>It is not possible to customize the error log by adding or 117 removing information. However, error log entries dealing with 118 particular requests have corresponding entries in the <a href="#accesslog">access log</a>. For example, the above example 119 entry corresponds to an access log entry with status code 403. 120 Since it is possible to customize the access log, you can 121 obtain more information about error conditions using that log 122 file.</p> 123 124 <p>During testing, it is often useful to continuously monitor 125 the error log for any problems. On Unix systems, you can 126 accomplish this using:</p> 127 128 <div class="example"><p><code> 129 tail -f error_log 130 </code></p></div> 131 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 132<div class="section"> 133<h2><a name="accesslog" id="accesslog">Access Log</a></h2> 134 135 136 <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> 137 138 <p>The server access log records all requests processed by the 139 server. The location and content of the access log are 140 controlled by the <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> 141 directive. The <code class="directive"><a href="/mod/mod_log_config.html#logformat">LogFormat</a></code> 142 directive can be used to simplify the selection of 143 the contents of the logs. This section describes how to configure the server 144 to record information in the access log.</p> 145 146 <p>Of course, storing the information in the access log is only 147 the start of log management. The next step is to analyze this 148 information to produce useful statistics. Log analysis in 149 general is beyond the scope of this document, and not really 150 part of the job of the web server itself. For more information 151 about this topic, and for applications which perform log 152 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/"> 153 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/"> 154 Yahoo</a>.</p> 155 156 <p>Various versions of Apache httpd have used other modules and 157 directives to control access logging, including 158 mod_log_referer, mod_log_agent, and the 159 <code>TransferLog</code> directive. The <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> directive now subsumes 160 the functionality of all the older directives.</p> 161 162 <p>The format of the access log is highly configurable. The format 163 is specified using a format string that looks much like a C-style 164 printf(1) format string. Some examples are presented in the next 165 sections. For a complete list of the possible contents of the 166 format string, see the <code class="module"><a href="/mod/mod_log_config.html">mod_log_config</a></code> <a href="mod/mod_log_config.html#formats">format strings</a>.</p> 167 168 <h3><a name="common" id="common">Common Log Format</a></h3> 169 170 171 <p>A typical configuration for the access log might look as 172 follows.</p> 173 174 <div class="example"><p><code> 175 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br /> 176 CustomLog logs/access_log common 177 </code></p></div> 178 179 <p>This defines the <em>nickname</em> <code>common</code> and 180 associates it with a particular log format string. The format 181 string consists of percent directives, each of which tell the 182 server to log a particular piece of information. Literal 183 characters may also be placed in the format string and will be 184 copied directly into the log output. The quote character 185 (<code>"</code>) must be escaped by placing a backslash before 186 it to prevent it from being interpreted as the end of the 187 format string. The format string may also contain the special 188 control characters "<code>\n</code>" for new-line and 189 "<code>\t</code>" for tab.</p> 190 191 <p>The <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> 192 directive sets up a new log file using the defined 193 <em>nickname</em>. The filename for the access log is relative to 194 the <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code> unless it 195 begins with a slash.</p> 196 197 <p>The above configuration will write log entries in a format 198 known as the Common Log Format (CLF). This standard format can 199 be produced by many different web servers and read by many log 200 analysis programs. The log file entries produced in CLF will 201 look something like this:</p> 202 203 <div class="example"><p><code> 204 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET 205 /apache_pb.gif HTTP/1.0" 200 2326 206 </code></p></div> 207 208 <p>Each part of this log entry is described below.</p> 209 210 <dl> 211 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt> 212 213 <dd>This is the IP address of the client (remote host) which 214 made the request to the server. If <code class="directive"><a href="/mod/core.html#hostnamelookups">HostnameLookups</a></code> is 215 set to <code>On</code>, then the server will try to determine 216 the hostname and log it in place of the IP address. However, 217 this configuration is not recommended since it can 218 significantly slow the server. Instead, it is best to use a 219 log post-processor such as <code class="program"><a href="/programs/logresolve.html">logresolve</a></code> to determine 220 the hostnames. The IP address reported here is not 221 necessarily the address of the machine at which the user is 222 sitting. If a proxy server exists between the user and the 223 server, this address will be the address of the proxy, rather 224 than the originating machine.</dd> 225 226 <dt><code>-</code> (<code>%l</code>)</dt> 227 228 <dd>The "hyphen" in the output indicates that the requested 229 piece of information is not available. In this case, the 230 information that is not available is the RFC 1413 identity of 231 the client determined by <code>identd</code> on the clients 232 machine. This information is highly unreliable and should 233 almost never be used except on tightly controlled internal 234 networks. Apache httpd will not even attempt to determine 235 this information unless <code class="directive"><a href="/mod/mod_ident.html#identitycheck">IdentityCheck</a></code> is set 236 to <code>On</code>.</dd> 237 238 <dt><code>frank</code> (<code>%u</code>)</dt> 239 240 <dd>This is the userid of the person requesting the document 241 as determined by HTTP authentication. The same value is 242 typically provided to CGI scripts in the 243 <code>REMOTE_USER</code> environment variable. If the status 244 code for the request (see below) is 401, then this value 245 should not be trusted because the user is not yet 246 authenticated. If the document is not password protected, 247 this part will be "<code>-</code>" just like the previous 248 one.</dd> 249 250 <dt><code>[10/Oct/2000:13:55:36 -0700]</code> 251 (<code>%t</code>)</dt> 252 253 <dd> 254 The time that the request was received. 255 The format is: 256 257 <p class="indent"> 258 <code>[day/month/year:hour:minute:second zone]<br /> 259 day = 2*digit<br /> 260 month = 3*letter<br /> 261 year = 4*digit<br /> 262 hour = 2*digit<br /> 263 minute = 2*digit<br /> 264 second = 2*digit<br /> 265 zone = (`+' | `-') 4*digit</code> 266 </p> 267 It is possible to have the time displayed in another format 268 by specifying <code>%{format}t</code> in the log format 269 string, where <code>format</code> is as in 270 <code>strftime(3)</code> from the C standard library. 271 </dd> 272 273 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code> 274 (<code>\"%r\"</code>)</dt> 275 276 <dd>The request line from the client is given in double 277 quotes. The request line contains a great deal of useful 278 information. First, the method used by the client is 279 <code>GET</code>. Second, the client requested the resource 280 <code>/apache_pb.gif</code>, and third, the client used the 281 protocol <code>HTTP/1.0</code>. It is also possible to log 282 one or more parts of the request line independently. For 283 example, the format string "<code>%m %U%q %H</code>" will log 284 the method, path, query-string, and protocol, resulting in 285 exactly the same output as "<code>%r</code>".</dd> 286 287 <dt><code>200</code> (<code>%>s</code>)</dt> 288 289 <dd>This is the status code that the server sends back to the 290 client. This information is very valuable, because it reveals 291 whether the request resulted in a successful response (codes 292 beginning in 2), a redirection (codes beginning in 3), an 293 error caused by the client (codes beginning in 4), or an 294 error in the server (codes beginning in 5). The full list of 295 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP 296 specification</a> (RFC2616 section 10).</dd> 297 298 <dt><code>2326</code> (<code>%b</code>)</dt> 299 300 <dd>The last part indicates the size of the object returned 301 to the client, not including the response headers. If no 302 content was returned to the client, this value will be 303 "<code>-</code>". To log "<code>0</code>" for no content, use 304 <code>%B</code> instead.</dd> 305 </dl> 306 307 308 <h3><a name="combined" id="combined">Combined Log Format</a></h3> 309 310 311 <p>Another commonly used format string is called the Combined 312 Log Format. It can be used as follows.</p> 313 314 <div class="example"><p><code> 315 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" 316 \"%{User-agent}i\"" combined<br /> 317 CustomLog log/access_log combined 318 </code></p></div> 319 320 <p>This format is exactly the same as the Common Log Format, 321 with the addition of two more fields. Each of the additional 322 fields uses the percent-directive 323 <code>%{<em>header</em>}i</code>, where <em>header</em> can be 324 any HTTP request header. The access log under this format will 325 look like:</p> 326 327 <div class="example"><p><code> 328 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET 329 /apache_pb.gif HTTP/1.0" 200 2326 330 "http://www.example.com/start.html" "Mozilla/4.08 [en] 331 (Win98; I ;Nav)" 332 </code></p></div> 333 334 <p>The additional fields are:</p> 335 336 <dl> 337 <dt><code>"http://www.example.com/start.html"</code> 338 (<code>\"%{Referer}i\"</code>)</dt> 339 340 <dd>The "Referer" (sic) HTTP request header. This gives the 341 site that the client reports having been referred from. (This 342 should be the page that links to or includes 343 <code>/apache_pb.gif</code>).</dd> 344 345 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code> 346 (<code>\"%{User-agent}i\"</code>)</dt> 347 348 <dd>The User-Agent HTTP request header. This is the 349 identifying information that the client browser reports about 350 itself.</dd> 351 </dl> 352 353 354 <h3><a name="multiple" id="multiple">Multiple Access Logs</a></h3> 355 356 357 <p>Multiple access logs can be created simply by specifying 358 multiple <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> 359 directives in the configuration 360 file. For example, the following directives will create three 361 access logs. The first contains the basic CLF information, 362 while the second and third contain referer and browser 363 information. The last two <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> lines show how 364 to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p> 365 366 <div class="example"><p><code> 367 LogFormat "%h %l %u %t \"%r\" %>s %b" common<br /> 368 CustomLog logs/access_log common<br /> 369 CustomLog logs/referer_log "%{Referer}i -> %U"<br /> 370 CustomLog logs/agent_log "%{User-agent}i" 371 </code></p></div> 372 373 <p>This example also shows that it is not necessary to define a 374 nickname with the <code class="directive"><a href="/mod/mod_log_config.html#logformat">LogFormat</a></code> directive. Instead, 375 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> 376 377 378 <h3><a name="conditional" id="conditional">Conditional Logs</a></h3> 379 380 381 <p>There are times when it is convenient to exclude certain 382 entries from the access logs based on characteristics of the 383 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an 384 environment variable must be set to indicate that the request 385 meets certain conditions. This is usually accomplished with 386 <code class="directive"><a href="/mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>. Then the 387 <code>env=</code> clause of the <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> directive is used to 388 include or exclude requests where the environment variable is 389 set. Some examples:</p> 390 391 <div class="example"><p><code> 392 # Mark requests from the loop-back interface<br /> 393 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br /> 394 # Mark requests for the robots.txt file<br /> 395 SetEnvIf Request_URI "^/robots\.txt$" dontlog<br /> 396 # Log what remains<br /> 397 CustomLog logs/access_log common env=!dontlog 398 </code></p></div> 399 400 <p>As another example, consider logging requests from 401 english-speakers to one log file, and non-english speakers to a 402 different log file.</p> 403 404 <div class="example"><p><code> 405 SetEnvIf Accept-Language "en" english<br /> 406 CustomLog logs/english_log common env=english<br /> 407 CustomLog logs/non_english_log common env=!english 408 </code></p></div> 409 410 <p>Although we have just shown that conditional logging is very 411 powerful and flexible, it is not the only way to control the 412 contents of the logs. Log files are more useful when they 413 contain a complete record of server activity. It is often 414 easier to simply post-process the log files to remove requests 415 that you do not want to consider.</p> 416 417 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 418<div class="section"> 419<h2><a name="rotation" id="rotation">Log Rotation</a></h2> 420 421 422 <p>On even a moderately busy server, the quantity of 423 information stored in the log files is very large. The access 424 log file typically grows 1 MB or more per 10,000 requests. It 425 will consequently be necessary to periodically rotate the log 426 files by moving or deleting the existing logs. This cannot be 427 done while the server is running, because Apache will continue 428 writing to the old log file as long as it holds the file open. 429 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are 430 moved or deleted so that it will open new log files.</p> 431 432 <p>By using a <em>graceful</em> restart, the server can be 433 instructed to open new log files without losing any existing or 434 pending connections from clients. However, in order to 435 accomplish this, the server must continue to write to the old 436 log files while it finishes serving old requests. It is 437 therefore necessary to wait for some time after the restart 438 before doing any processing on the log files. A typical 439 scenario that simply rotates the logs and compresses the old 440 logs to save space is:</p> 441 442 <div class="example"><p><code> 443 mv access_log access_log.old<br /> 444 mv error_log error_log.old<br /> 445 apachectl graceful<br /> 446 sleep 600<br /> 447 gzip access_log.old error_log.old 448 </code></p></div> 449 450 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next 451 section.</p> 452 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 453<div class="section"> 454<h2><a name="piped" id="piped">Piped Logs</a></h2> 455 456 457 <p>Apache httpd is capable of writing error and access log 458 files through a pipe to another process, rather than directly 459 to a file. This capability dramatically increases the 460 flexibility of logging, without adding code to the main server. 461 In order to write logs to a pipe, simply replace the filename 462 with the pipe character "<code>|</code>", followed by the name 463 of the executable which should accept log entries on its 464 standard input. Apache will start the piped-log process when 465 the server starts, and will restart it if it crashes while the 466 server is running. (This last feature is why we can refer to 467 this technique as "reliable piped logging".)</p> 468 469 <p>Piped log processes are spawned by the parent Apache httpd 470 process, and inherit the userid of that process. This means 471 that piped log programs usually run as root. It is therefore 472 very important to keep the programs simple and secure.</p> 473 474 <p>One important use of piped logs is to allow log rotation 475 without having to restart the server. The Apache HTTP Server 476 includes a simple program called <code class="program"><a href="/programs/rotatelogs.html">rotatelogs</a></code> 477 for this purpose. For example, to rotate the logs every 24 hours, you 478 can use:</p> 479 480 <div class="example"><p><code> 481 CustomLog "|/usr/local/apache/bin/rotatelogs 482 /var/log/access_log 86400" common 483 </code></p></div> 484 485 <p>Notice that quotes are used to enclose the entire command 486 that will be called for the pipe. Although these examples are 487 for the access log, the same technique can be used for the 488 error log.</p> 489 490 <p>A similar but much more flexible log rotation program 491 called <a href="http://www.cronolog.org/">cronolog</a> 492 is available at an external site.</p> 493 494 <p>As with conditional logging, piped logs are a very powerful 495 tool, but they should not be used where a simpler solution like 496 off-line post-processing is available.</p> 497 498 <p>By default the piped log process is spawned using a shell. 499 (usually with <code>/bin/sh -c</code>). 500 Depending on the shell specifics invocation via shell might 501 lead to an additional shell process for the lifetime of the 502 logging pipe program and signal handling problems during 503 restart.</p> 504 505 <p>Use "<code>||</code>" instead of "<code>|</code>" 506 to spawn without invoking a shell:</p> 507 508 <div class="example"><p><code> 509 # Invoke "rotatelogs" without using a shell<br /> 510 CustomLog "||/usr/local/apache/bin/rotatelogs 511 /var/log/access_log 86400" common 512 </code></p></div> 513 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 514<div class="section"> 515<h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2> 516 517 518 <p>When running a server with many <a href="vhosts/">virtual 519 hosts</a>, there are several options for dealing with log 520 files. First, it is possible to use logs exactly as in a 521 single-host server. Simply by placing the logging directives 522 outside the <code class="directive"><a href="/mod/core.html#virtualhost"><VirtualHost></a></code> sections in the 523 main server context, it is possible to log all requests in the 524 same access log and error log. This technique does not allow 525 for easy collection of statistics on individual virtual 526 hosts.</p> 527 528 <p>If <code class="directive"><a href="/mod/mod_log_config.html#customlog">CustomLog</a></code> 529 or <code class="directive"><a href="/mod/core.html#errorlog">ErrorLog</a></code> 530 directives are placed inside a 531 <code class="directive"><a href="/mod/core.html#virtualhost"><VirtualHost></a></code> 532 section, all requests or errors for that virtual host will be 533 logged only to the specified file. Any virtual host which does 534 not have logging directives will still have its requests sent 535 to the main server logs. This technique is very useful for a 536 small number of virtual hosts, but if the number of hosts is 537 very large, it can be complicated to manage. In addition, it 538 can often create problems with <a href="vhosts/fd-limits.html">insufficient file 539 descriptors</a>.</p> 540 541 <p>For the access log, there is a very good compromise. By 542 adding information on the virtual host to the log format 543 string, it is possible to log all hosts to the same log, and 544 later split the log into individual files. For example, 545 consider the following directives.</p> 546 547 <div class="example"><p><code> 548 LogFormat "%v %l %u %t \"%r\" %>s %b" 549 comonvhost<br /> 550 CustomLog logs/access_log comonvhost 551 </code></p></div> 552 553 <p>The <code>%v</code> is used to log the name of the virtual 554 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to 555 post-process the access log in order to split it into one file 556 per virtual host.</p> 557 </div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 558<div class="section"> 559<h2><a name="other" id="other">Other Log Files</a></h2> 560 561 562 <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="/mod/mod_logio.html">mod_logio</a></code></li><li><code class="module"><a href="/mod/mod_log_forensic.html">mod_log_forensic</a></code></li><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><li><code class="module"><a href="/mod/mod_log_config.html">mod_log_config</a></code></li></ul></td><td><ul><li><code class="directive"><a href="/mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="/mod/mod_log_config.html#bufferedlogs">BufferedLogs</a></code></li><li><code class="directive"><a href="/mod/mod_log_forensic.html#forensiclog">ForensicLog</a></code></li><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> 563 564 <h3>Logging actual bytes sent and received</h3> 565 566 567 <p><code class="module"><a href="/mod/mod_logio.html">mod_logio</a></code> adds in two additional 568 <code class="directive"><a href="/mod/mod_log_config.html#logformat">LogFormat</a></code> fields 569 (%I and %O) that log the actual number of bytes received and sent 570 on the network.</p> 571 572 573 <h3>Forensic Logging</h3> 574 575 576 <p><code class="module"><a href="/mod/mod_log_forensic.html">mod_log_forensic</a></code> provides for forensic logging of 577 client requests. Logging is done before and after processing a 578 request, so the forensic log contains two log lines for each 579 request. The forensic logger is very strict with no customizations. 580 It can be an invaluable debugging and security tool.</p> 581 582 583 <h3><a name="pidfile" id="pidfile">PID File</a></h3> 584 585 586 <p>On startup, Apache httpd saves the process id of the parent 587 httpd process to the file <code>logs/httpd.pid</code>. This 588 filename can be changed with the <code class="directive"><a href="/mod/mpm_common.html#pidfile">PidFile</a></code> directive. The 589 process-id is for use by the administrator in restarting and 590 terminating the daemon by sending signals to the parent 591 process; on Windows, use the -k command line option instead. 592 For more information see the <a href="stopping.html">Stopping 593 and Restarting</a> page.</p> 594 595 596 <h3><a name="scriptlog" id="scriptlog">Script Log</a></h3> 597 598 599 <p>In order to aid in debugging, the 600 <code class="directive"><a href="/mod/mod_cgi.html#scriptlog">ScriptLog</a></code> directive 601 allows you to record the input to and output from CGI scripts. 602 This should only be used in testing - not for live servers. 603 More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p> 604 605 606 <h3><a name="rewritelog" id="rewritelog">Rewrite Log</a></h3> 607 608 609 <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost 610 always necessary to use the <code class="directive"><a href="/mod/mod_rewrite.html#rewritelog">RewriteLog</a></code> to help 611 in debugging. This log file produces a detailed analysis of how 612 the rewriting engine transforms requests. The level of detail 613 is controlled by the <code class="directive"><a href="/mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code> directive.</p> 614 615 </div></div> 616<div class="bottomlang"> 617<p><span>Available Languages: </span><a href="/en/logs.html" title="English"> en </a> | 618<a href="/fr/logs.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 619<a href="/ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 620<a href="/ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | 621<a href="/tr/logs.html" hreflang="tr" rel="alternate" title="T�rk�e"> tr </a></p> 622</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. 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