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  10. <title>Stopping and Restarting Apache HTTP Server - Apache HTTP Server Version 2.5</title>
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  18. <body id="manual-page"><div id="page-header">
    19. 

  19. <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/quickreference.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>
    20. 

  20. <p class="apache">Apache HTTP Server Version 2.5</p>
    21. 

  21. <img alt="" src="./images/feather.png" /></div>
    22. 

  22. <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="./images/left.gif" /></a></div>
    23. 

  23. <div id="path">
    24. 

  24. <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="./">Version 2.5</a></div><div id="page-content"><div id="preamble"><h1>Stopping and Restarting Apache HTTP Server</h1>
    25. 

  25. <div class="toplang">
    26. 

  26. <p><span>Available Languages: </span><a href="./de/stopping.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
    27. 

  27. <a href="./en/stopping.html" title="English">&nbsp;en&nbsp;</a> |
    28. 

  28. <a href="./es/stopping.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
    29. 

  29. <a href="./fr/stopping.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
    30. 

  30. <a href="./ja/stopping.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
    31. 

  31. <a href="./ko/stopping.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a> |
    32. 

  32. <a href="./tr/stopping.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
    33. 

  33. </div>
    34. 

  34. 

  35.     <p>This document covers stopping and restarting Apache HTTP Server on
    36. 

  36.     Unix-like systems. Windows NT, 2000 and XP users should see
    37. 

  37.     <a href="platform/windows.html#winsvc">Running httpd as a
    38. 

  38.     Service</a> and Windows 9x and ME users should see <a href="platform/windows.html#wincons">Running httpd as a
    39. 

  39.     Console Application</a> for information on how to control
    40. 

  40.     httpd on those platforms.</p>
    41. 

  41. </div>
    42. 

  42. <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#introduction">Introduction</a></li>
    43. 

  43. <li><img alt="" src="./images/down.gif" /> <a href="#term">Stop Now</a></li>
    44. 

  44. <li><img alt="" src="./images/down.gif" /> <a href="#graceful">Graceful Restart</a></li>
    45. 

  45. <li><img alt="" src="./images/down.gif" /> <a href="#hup">Restart Now</a></li>
    46. 

  46. <li><img alt="" src="./images/down.gif" /> <a href="#gracefulstop">Graceful Stop</a></li>
    47. 

  47. </ul><h3>See also</h3><ul class="seealso"><li><code class="program"><a href="./programs/httpd.html">httpd</a></code></li><li><code class="program"><a href="./programs/apachectl.html">apachectl</a></code></li><li><a href="invoking.html">Starting</a></li><li><a href="#comments_section">Comments</a></li></ul></div>
    48. 

  48. <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
    49. 

  49. <div class="section">
    50. 

  50. <h2><a name="introduction" id="introduction">Introduction</a></h2>
    51. 

  51. 

  52.     <p>In order to stop or restart the Apache HTTP Server, you must send a signal to
    53. 

  53.     the running <code class="program"><a href="./programs/httpd.html">httpd</a></code> processes.  There are two ways to
    54. 

  54.     send the signals.  First, you can use the unix <code>kill</code>
    55. 

  55.     command to directly send signals to the processes. You will
    56. 

  56.     notice many <code class="program"><a href="./programs/httpd.html">httpd</a></code> executables running on your system,
    57. 

  57.     but you should not send signals to any of them except the parent,
    58. 

  58.     whose pid is in the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code>. That is to say you
    59. 

  59.     shouldn't ever need to send signals to any process except the
    60. 

  60.     parent. There are four signals that you can send the parent:
    61. 

  61.     <code><a href="#term">TERM</a></code>,
    62. 

  62.     <code><a href="#graceful">USR1</a></code>,
    63. 

  63.     <code><a href="#hup">HUP</a></code>, and
    64. 

  64.     <code><a href="#gracefulstop">WINCH</a></code>, which
    65. 

  65.     will be described in a moment.</p>
    66. 

  66. 

  67.     <p>To send a signal to the parent you should issue a command
    68. 

  68.     such as:</p>
    69. 

  69. 

  70. <div class="example"><p><code>kill -TERM `cat /usr/local/apache2/logs/httpd.pid`</code></p></div>
    71. 

  71. 

  72.     <p>The second method of signaling the <code class="program"><a href="./programs/httpd.html">httpd</a></code> processes
    73. 

  73.     is to use the <code>-k</code> command line options: <code>stop</code>,
    74. 

  74.     <code>restart</code>, <code>graceful</code> and <code>graceful-stop</code>,
    75. 

  75.     as described below.  These are arguments to the <code class="program"><a href="./programs/httpd.html">httpd</a></code> binary, but we recommend that
    76. 

  76.     you send them using the <code class="program"><a href="./programs/apachectl.html">apachectl</a></code> control script, which
    77. 

  77.     will pass them through to <code class="program"><a href="./programs/httpd.html">httpd</a></code>.</p>
    78. 

  78. 

  79.     <p>After you have signaled <code class="program"><a href="./programs/httpd.html">httpd</a></code>, you can read about
    80. 

  80.     its progress by issuing:</p>
    81. 

  81. 

  82. <div class="example"><p><code>tail -f /usr/local/apache2/logs/error_log</code></p></div>
    83. 

  83. 

  84.     <p>Modify those examples to match your <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> and <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> settings.</p>
    85. 

  85. </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
    86. 

  86. <div class="section">
    87. 

  87. <h2><a name="term" id="term">Stop Now</a></h2>
    88. 

  88. 

  89. <dl><dt>Signal: TERM</dt>
    90. 

  90. <dd><code>apachectl -k stop</code></dd>
    91. 

  91. </dl>
    92. 

  92. 

  93.     <p>Sending the <code>TERM</code> or <code>stop</code> signal to
    94. 

  94.     the parent causes it to immediately attempt to kill off all of its
    95. 

  95.     children. It may take it several seconds to complete killing off
    96. 

  96.     its children.  Then the parent itself exits. Any requests in
    97. 

  97.     progress are terminated, and no further requests are served.</p>
    98. 

  98. </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
    99. 

  99. <div class="section">
    100. 

  100. <h2><a name="graceful" id="graceful">Graceful Restart</a></h2>
    101. 

  101. 

  102. <dl><dt>Signal: USR1</dt>
    103. 

  103. <dd><code>apachectl -k graceful</code></dd>
    104. 

  104. </dl>
    105. 

  105. 

  106.     <p>The <code>USR1</code> or <code>graceful</code> signal causes
    107. 

  107.     the parent process to <em>advise</em> the children to exit after
    108. 

  108.     their current request (or to exit immediately if they're not
    109. 

  109.     serving anything). The parent re-reads its configuration files and
    110. 

  110.     re-opens its log files. As each child dies off the parent replaces
    111. 

  111.     it with a child from the new <em>generation</em> of the
    112. 

  112.     configuration, which begins serving new requests immediately.</p>
    113. 

  113. 

  114.     <p>This code is designed to always respect the process control
    115. 

  115.     directive of the MPMs, so the number of processes and threads
    116. 

  116.     available to serve clients will be maintained at the appropriate
    117. 

  117.     values throughout the restart process.  Furthermore, it respects
    118. 

  118.     <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code> in the
    119. 

  119.     following manner: if after one second at least <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code> new children have not
    120. 

  120.     been created, then create enough to pick up the slack. Hence the
    121. 

  121.     code tries to maintain both the number of children appropriate for
    122. 

  122.     the current load on the server, and respect your wishes with the
    123. 

  123.     <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code>
    124. 

  124.     parameter.</p>
    125. 

  125. 

  126.     <p>Users of <code class="module"><a href="./mod/mod_status.html">mod_status</a></code>
    127. 

  127.     will notice that the server statistics are <strong>not</strong>
    128. 

  128.     set to zero when a <code>USR1</code> is sent. The code was
    129. 

  129.     written to both minimize the time in which the server is unable
    130. 

  130.     to serve new requests (they will be queued up by the operating
    131. 

  131.     system, so they're not lost in any event) and to respect your
    132. 

  132.     tuning parameters. In order to do this it has to keep the
    133. 

  133.     <em>scoreboard</em> used to keep track of all children across
    134. 

  134.     generations.</p>
    135. 

  135. 

  136.     <p>The status module will also use a <code>G</code> to indicate
    137. 

  137.     those children which are still serving requests started before
    138. 

  138.     the graceful restart was given.</p>
    139. 

  139. 

  140.     <p>At present there is no way for a log rotation script using
    141. 

  141.     <code>USR1</code> to know for certain that all children writing
    142. 

  142.     the pre-restart log have finished. We suggest that you use a
    143. 

  143.     suitable delay after sending the <code>USR1</code> signal
    144. 

  144.     before you do anything with the old log. For example if most of
    145. 

  145.     your hits take less than 10 minutes to complete for users on
    146. 

  146.     low bandwidth links then you could wait 15 minutes before doing
    147. 

  147.     anything with the old log.</p>
    148. 

  148. 

  149.     <div class="note">
    150. 

  150.     <p>When you issue a restart, a syntax check is first run, to
    151. 

  151.     ensure that there are no errors in the configuration files.
    152. 

  152.     If your configuration file has errors in it, you will get an
    153. 

  153.     error message about that syntax error, and the server will refuse to
    154. 

  154.     restart. This avoids the situation where the server halts and then
    155. 

  155.     cannot restart, leaving you with a non-functioning server.</p>
    156. 

  156. 

  157.     <p>This still will not
    158. 

  158.     guarantee that the server will restart correctly. To check the
    159. 

  159.     semantics of the configuration files as well as the syntax, you
    160. 

  160.     can try starting <code class="program"><a href="./programs/httpd.html">httpd</a></code> as a non-root user. If there
    161. 

  161.     are no errors it will attempt to open its sockets and logs and fail
    162. 

  162.     because it's not root (or because the currently running
    163. 

  163.     <code class="program"><a href="./programs/httpd.html">httpd</a></code> already has those ports bound). If it fails
    164. 

  164.     for any other reason then it's probably a config file error and the error
    165. 

  165.     should be fixed before issuing the graceful restart.</p></div>
    166. 

  166. </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
    167. 

  167. <div class="section">
    168. 

  168. <h2><a name="hup" id="hup">Restart Now</a></h2>
    169. 

  169. 

  170. <dl><dt>Signal: HUP</dt>
    171. 

  171. <dd><code>apachectl -k restart</code></dd>
    172. 

  172. </dl>
    173. 

  173. 

  174.     <p>Sending the <code>HUP</code> or <code>restart</code> signal to
    175. 

  175.     the parent causes it to kill off its children like in
    176. 

  176.     <code>TERM</code>, but the parent doesn't exit. It re-reads its
    177. 

  177.     configuration files, and re-opens any log files. Then it spawns a
    178. 

  178.     new set of children and continues serving hits.</p>
    179. 

  179. 

  180.     <p>Users of <code class="module"><a href="./mod/mod_status.html">mod_status</a></code>
    181. 

  181.     will notice that the server statistics are set to zero when a
    182. 

  182.     <code>HUP</code> is sent.</p>
    183. 

  183. 

  184. <div class="note">As with a graceful restart, a syntax check is run before the
    185. 

  185. restart is attempted. If your configuration file has errors in it, the
    186. 

  186. restart will not be attempted, and you will receive notification of the
    187. 

  187. syntax error(s).</div>
    188. 

  188. </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
    189. 

  189. <div class="section">
    190. 

  190. <h2><a name="gracefulstop" id="gracefulstop">Graceful Stop</a></h2>
    191. 

  191. 

  192. <dl><dt>Signal: WINCH</dt>
    193. 

  193. <dd><code>apachectl -k graceful-stop</code></dd>
    194. 

  194. </dl>
    195. 

  195. 

  196.     <p>The <code>WINCH</code> or <code>graceful-stop</code> signal causes
    197. 

  197.     the parent process to <em>advise</em> the children to exit after
    198. 

  198.     their current request (or to exit immediately if they're not
    199. 

  199.     serving anything). The parent will then remove its <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> and cease listening on
    200. 

  200.     all ports. The parent will continue to run, and monitor children
    201. 

  201.     which are handling requests. Once all children have finalised
    202. 

  202.     and exited or the timeout specified by the <code class="directive"><a href="./mod/mpm_common.html#gracefulshutdowntimeout">GracefulShutdownTimeout</a></code> has been
    203. 

  203.     reached, the parent will also exit.  If the timeout is reached,
    204. 

  204.     any remaining children will be sent the <code>TERM</code> signal
    205. 

  205.     to force them to exit.</p>
    206. 

  206. 

  207.     <p>A <code>TERM</code> signal will immediately terminate the
    208. 

  208.     parent process and all children when in the "graceful" state. However
    209. 

  209.     as the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> will
    210. 

  210.     have been removed, you will not be able to use
    211. 

  211.     <code>apachectl</code> or <code>httpd</code> to send this signal.</p>
    212. 

  212. 

  213.     <div class="note"><p>The <code>graceful-stop</code> signal allows you to run multiple
    214. 

  214.     identically configured instances of <code class="program"><a href="./programs/httpd.html">httpd</a></code> at the
    215. 

  215.     same time. This is a powerful feature when performing graceful
    216. 

  216.     upgrades of httpd, however it can also cause deadlocks and race
    217. 

  217.     conditions with some configurations.</p>
    218. 

  218. 

  219.     <p>Care has been taken to ensure that on-disk files such as lock files
    220. 

  220.     (<code class="directive"><a href="./mod/core.html#mutex">Mutex</a></code>) and Unix socket files
    221. 

  221.     (<code class="directive"><a href="./mod/mod_cgid.html#scriptsock">ScriptSock</a></code>) contain the server
    222. 

  222.     PID, and should coexist without problem. However, if a configuration
    223. 

  223.     directive, third-party module or persistent CGI utilises any other on-disk
    224. 

  224.     lock or  state files, care should be taken to ensure that multiple running
    225. 

  225.     instances of <code class="program"><a href="./programs/httpd.html">httpd</a></code> do not clobber each other's files.</p>
    226. 

    227. 

  227.     <p>You should also be wary of other potential race conditions, such as
    228. 

  228.     using <code class="program"><a href="./programs/rotatelogs.html">rotatelogs</a></code> style piped logging. Multiple running
    229. 

  229.     instances of <code class="program"><a href="./programs/rotatelogs.html">rotatelogs</a></code> attempting to rotate the same
    230. 

  230.     logfiles at the same time may destroy each other's logfiles.</p></div>
    231. 

  231. </div></div>
    232. 

  232. <div class="bottomlang">
    233. 

  233. <p><span>Available Languages: </span><a href="./de/stopping.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
    234. 

  234. <a href="./en/stopping.html" title="English">&nbsp;en&nbsp;</a> |
    235. 

  235. <a href="./es/stopping.html" hreflang="es" rel="alternate" title="Español">&nbsp;es&nbsp;</a> |
    236. 

  236. <a href="./fr/stopping.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
    237. 

  237. <a href="./ja/stopping.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
    238. 

  238. <a href="./ko/stopping.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a> |
    239. 

  239. <a href="./tr/stopping.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
    240. 

  240. </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&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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