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><A
NAME="POSTMASTER-SHUTDOWN"
>16.5. Shutting Down the Server</A
></H1
><A
NAME="AEN18156"
></A
><P
> There are several ways to shut down the database server. You control
the type of shutdown by sending different signals to the
<TT
CLASS="COMMAND"
>postmaster</TT
> process.
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><SPAN
CLASS="SYSTEMITEM"
>SIGTERM</SPAN
><A
NAME="AEN18164"
></A
></DT
><DD
><P
> 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 normally. This is the <I
CLASS="FIRSTTERM"
>Smart
Shutdown</I
>.
</P
></DD
><DT
><SPAN
CLASS="SYSTEMITEM"
>SIGINT</SPAN
><A
NAME="AEN18173"
></A
></DT
><DD
><P
> 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 the server processes to exit and finally shuts down. This is the
<I
CLASS="FIRSTTERM"
>Fast Shutdown</I
>.
</P
></DD
><DT
><SPAN
CLASS="SYSTEMITEM"
>SIGQUIT</SPAN
><A
NAME="AEN18182"
></A
></DT
><DD
><P
> This is the <I
CLASS="FIRSTTERM"
>Immediate Shutdown</I
>, which
will cause the <TT
CLASS="COMMAND"
>postmaster</TT
> process to 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
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</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.
</P
><P
> Alternatively, you can send the signal directly using <TT
CLASS="COMMAND"
>kill</TT
>.
The <ACRONYM
CLASS="ACRONYM"
>PID</ACRONYM
> of the <TT
CLASS="COMMAND"
>postmaster</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
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><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 may then have to be done
manually before a new server can be started. Furthermore,
<SPAN
CLASS="SYSTEMITEM"
>SIGKILL</SPAN
> kills the <TT
CLASS="COMMAND"
>postmaster</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
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