Apache MPM Common Directives

See usage for the default setting

directory, which should not be writable by the user the server runs as.ServerRoot

If you want a core dump for debugging, you can use this directive to place it in a different location. This directive has no effect if your operating system is not configured to write core files to the working directory of the crashing processes.

If Apache httpd starts as root and switches to another user, the Linux kernel disables core dumps even if the directory is writable for the process. Apache httpd (2.0.46 and later) reenables core dumps on Linux 2.4 and beyond, but only if you explicitly configure a CoreDumpDirectory

To enable core-dumping of suid-executables on BSD-systems (such as FreeBSD), set kern.sugid_coredump

processing only occurs for a select set of fatal signals: SIGFPE, SIGILL, SIGABORT, SIGSEGV, and SIGBUS.

On some operating systems, SIGQUIT also results in a core dump but does not go through CoreDumpDirectory

There are already two modules, mod_whatkilledus

that make use of this hook. Please have a look at Jeff Trawick's EnableExceptionHook site for more information about these.

Setting this value to zero means that the server will wait indefinitely until all remaining requests have been fully served.

Listen [IP-address:]portnumber [protocol]

directive tells the server to accept incoming requests on the specified port or address-and-port combination. If only a port number is specified, the server listens to the given port on all interfaces. If an IP address is given as well as a port, the server will listen on the given port and interface.

directives may be used to specify a number of addresses and ports to listen to. The server will respond to requests from any of the listed addresses and ports.

For example, to make the server accept connections on both port 80 and port 8000, use:

Listen 192.170.2.1:80 Listen 192.170.2.5:8000

IPv6 addresses must be surrounded in square brackets, as in the following example:

Listen [2001:db8::a00:20ff:fea7:ccea]:80

The optional protocol argument is not required for most configurations. If not specified, https

the default for all other ports. The protocol is used to determine which module should handle a request, and to apply protocol specific optimizations with the

You only need to set the protocol if you are running on non-standard ports. For example, running an https

directives for the same ip address and port will result in an Address already in use

This will often be limited to a smaller number by the operating system. This varies from OS to OS. Also note that many OSes do not use exactly what is specified as the backlog, but use a number based on (but normally larger than) what is set.

is still supported.The MaxConnectionsPerChild

to a non-zero value limits the amount of memory that process can consume by (accidental) memory leakage.

translates into the maximum number of child processes that will be launched to serve requests. The default value is 256

For threaded and hybrid servers (e.g.

restricts the total number of threads that will be available to serve clients. For hybrid MPMs the default value is 16

) multiplied by the value of ServerLimit25

). Therefore, to increase ThreadsPerChildMaxRequestWorkers

to a value that requires more than 16 processes, you must also raise

, the default is workerMaxSpareThreads 250

. This MPM deals with idle threads on a server-wide basis. If there are too many idle threads in the server then child processes are killed until the number of idle threads is less than this number.

the default is mpm_netwareMaxSpareThreads 100

. Since this MPM runs a single-process, the spare thread count is also server-wide.

works similar to mpmt_os2

value is restricted. Apache httpd will correct the given value automatically according to the following rules:

wants the value to be greater than MinSpareThreads

and, since it is a single-process MPM, tracks this on a server-wide bases.

PidFile logs/httpd.pid

It is often useful to be able to send the server a signal, so that it closes and then re-opens its

, and re-reads its configuration files. This is done by sending a SIGHUP (kill -1) signal to the process id listed in the TransferLogPidFile

is subject to the same warnings about log file placement and security.

script, or the init script that your OS provides, for (re-)starting or stopping the server.apache2ctl

Apache HTTP Server uses a scoreboard to communicate between its parent and child processes. Some architectures require a file to facilitate this communication. If the file is left unspecified, Apache httpd first attempts to create the scoreboard entirely in memory (using anonymous shared memory) and, failing that, will attempt to create the file on disk (using file-based shared memory). Specifying this directive causes Apache httpd to always create the file on the disk.

ScoreBoardFile /var/run/apacheruntimestatus

File-based shared memory is useful for third-party applications that require direct access to the scoreboard.

then you may see improved speed by placing it on a RAM disk. But be careful that you heed the same warnings about log file placement and security.

Further configuration of your operating system may be required to elicit better performance on high speed, high latency connections.

On some operating systems, changes in TCP behavior resulting from a larger SendBufferSize

may not be seen unless

is set to OFF. This interaction applies only to static files.EnableSendfile

Special care must be taken when using this directive. If ServerLimit

is set to a value much higher than necessary, extra, unused shared memory will be allocated. If both ServerLimit

are set to values higher than the system can handle, Apache httpd may not start or the system may become unstable.MaxRequestWorkers

MPM 200000). This is intended to avoid nasty effects caused by typos. To increase it even further past this limit, you will need to modify the value of MAXSERVERLIMIT in the mpm source file and rebuild the server.prefork

defaults to workerStartServers 3

the default is mpm_netwareStartThreads 50

are set to values higher than the system can handle, Apache httpd may not start or the system may become unstable. Do not set the value of this directive any higher than your greatest predicted setting of ThreadsPerChild

) compiled into the server. This is intended to avoid nasty effects caused by typos. To increase it even further past this limit, you will need to modify the value of MAXTHREADLIMIT in the mpm source file and rebuild the server.mpm_winnt

, where there are multiple child processes, the workertotal number of threads should be high enough to handle the common load on the server.

to a value higher than the operating system default. This type of adjustment is necessary only if the provider of the third-party module specifies that it is required, or if diagnosis of an Apache httpd crash indicates that the thread stack size was too small.ThreadStackSize

is set to a value lower than the operating system default. This type of adjustment should only be made in a test environment which allows the full set of web server processing can be exercised, as there may be infrequent requests which require more stack to process. The minimum required stack size strongly depends on the modules used, but any change in the web server configuration can invalidate the current ThreadStackSize

unless a high number of threads per child process is needed. On some platforms (including Linux), a setting of 128000 is already too low and causes crashes with some common modules.

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Apache HTTP Server Version 2.4