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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Shutting Down the Server</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.2.24 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Server Setup and Operation" HREF="runtime.html"><LINK REL="PREVIOUS" TITLE="Managing Kernel Resources" HREF="kernel-resources.html"><LINK REL="NEXT" TITLE="Upgrading a PostgreSQL Cluster" HREF="upgrading.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2017-11-06T22:43:11"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="5" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.2.24 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Managing Kernel Resources" HREF="kernel-resources.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="runtime.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 17. Server Setup and Operation</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Upgrading a PostgreSQL Cluster" HREF="upgrading.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="SERVER-SHUTDOWN" >17.5. Shutting Down the Server</A ></H1 ><P > There are several ways to shut down the database server. You control the type of shutdown by sending different signals to the master <TT CLASS="COMMAND" >postgres</TT > process. <P ></P ></P><DIV CLASS="VARIABLELIST" ><DL ><DT ><SPAN CLASS="SYSTEMITEM" >SIGTERM</SPAN ></DT ><DD ><P > This is the <I CLASS="FIRSTTERM" >Smart Shutdown</I > mode. After receiving <SPAN CLASS="SYSTEMITEM" >SIGTERM</SPAN >, the server disallows new connections, but lets existing sessions end their work normally. It shuts down only after all of the sessions terminate. If the server is in online backup mode, it additionally waits until online backup mode is no longer active. While backup mode is active, new connections will still be allowed, but only to superusers (this exception allows a superuser to connect to terminate online backup mode). If the server is in recovery when a smart shutdown is requested, recovery and streaming replication will be stopped only after all regular sessions have terminated. </P ></DD ><DT ><SPAN CLASS="SYSTEMITEM" >SIGINT</SPAN ></DT ><DD ><P > This is the <I CLASS="FIRSTTERM" >Fast Shutdown</I > mode. The server disallows new connections and sends all existing server processes <SPAN CLASS="SYSTEMITEM" >SIGTERM</SPAN >, which will cause them to abort their current transactions and exit promptly. It then waits for all server processes to exit and finally shuts down. If the server is in online backup mode, backup mode will be terminated, rendering the backup useless. </P ></DD ><DT ><SPAN CLASS="SYSTEMITEM" >SIGQUIT</SPAN ></DT ><DD ><P > This is the <I CLASS="FIRSTTERM" >Immediate Shutdown</I > mode. The master <TT CLASS="COMMAND" >postgres</TT > process will send a <SPAN CLASS="SYSTEMITEM" >SIGQUIT</SPAN > to all child processes and exit immediately, without properly shutting itself down. The child processes likewise exit immediately upon receiving <SPAN CLASS="SYSTEMITEM" >SIGQUIT</SPAN >. This will lead to recovery (by replaying the WAL log) upon next start-up. This is recommended only in emergencies. </P ></DD ></DL ></DIV ><P> </P ><P > The <A HREF="app-pg-ctl.html" ><SPAN CLASS="APPLICATION" >pg_ctl</SPAN ></A > program provides a convenient interface for sending these signals to shut down the server. Alternatively, you can send the signal directly using <TT CLASS="COMMAND" >kill</TT > on non-Windows systems. The <ACRONYM CLASS="ACRONYM" >PID</ACRONYM > of the <TT CLASS="COMMAND" >postgres</TT > process can be found using the <TT CLASS="COMMAND" >ps</TT > program, or from the file <TT CLASS="FILENAME" >postmaster.pid</TT > in the data directory. For example, to do a fast shutdown: </P><PRE CLASS="SCREEN" >$ <KBD CLASS="USERINPUT" >kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</KBD ></PRE ><P> </P ><DIV CLASS="IMPORTANT" ><BLOCKQUOTE CLASS="IMPORTANT" ><P ><B >Important: </B > It is best not to use <SPAN CLASS="SYSTEMITEM" >SIGKILL</SPAN > to shut down the server. Doing so will prevent the server from releasing shared memory and semaphores, which might then have to be done manually before a new server can be started. Furthermore, <SPAN CLASS="SYSTEMITEM" >SIGKILL</SPAN > kills the <TT CLASS="COMMAND" >postgres</TT > process without letting it relay the signal to its subprocesses, so it will be necessary to kill the individual subprocesses by hand as well. </P ></BLOCKQUOTE ></DIV ><P > To terminate an individual session while allowing other sessions to continue, use <CODE CLASS="FUNCTION" >pg_terminate_backend()</CODE > (see <A HREF="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL-TABLE" >Table 9-59</A >) or send a <SPAN CLASS="SYSTEMITEM" >SIGTERM</SPAN > signal to the child process associated with the session. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="kernel-resources.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="upgrading.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Managing Kernel Resources</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="runtime.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Upgrading a <SPAN CLASS="PRODUCTNAME" >PostgreSQL</SPAN > Cluster</TD ></TR ></TABLE ></DIV ></BODY ></HTML >