This file documents directives that are implemented by more than one multi-processing module (MPM).
Syntax:
ConnectionStatus on|off
Default:
ConnectionStatus on
Context: server config
Status: MPM
Module: perchild
Whether or not to maintain status information on current connections. If this is off then mod_status will not work properly.
Syntax: CoreDumpDirectory directory
Default: the same location as ServerRoot
Context: server config
Status: MPM
Module: threaded, perchild, prefork, mpm_winnt
This controls the directory to which Apache attempts to switch before dumping core. The default is in the ServerRoot directory, however since this should not be writable by the user the server runs as, core dumps won't normally get written. If you want a core dump for debugging, you can use this directive to place it in a different location.
Syntax: Group unix-group
Default: Group #-1
Context: server config, virtual host
Status: MPM
Module: threaded, perchild, prefork
nobody, but this is not always
possible or desirable.Note: if you start the server as a non-root user, it will fail to change to the specified group, and will instead continue to run as the group of the original user.
Special note: Use of this directive in <VirtualHost> requires a properly configured suEXEC wrapper. When used inside a <VirtualHost> in this manner, only the group that CGIs are run as is affected. Non-CGI requests are still processed as the group specified in the main Group directive.
SECURITY: See User for a discussion of the security considerations.
Syntax: PidFile filename
Default: PidFile logs/httpd.pid
Context: server config
Status: MPM
Module: threaded, perchild, prefork, mpm_winnt
The PidFile directive sets the file to which the server records the process id of the daemon. If the filename does not begin with a slash (/) then it is assumed to be relative to the ServerRoot.
It is often useful to be able to send the server a signal, so that it closes and then reopens its ErrorLog and TransferLog, and re-reads its configuration files. This is done by sending a SIGHUP (kill -1) signal to the process id listed in the PidFile.
The PidFile is subject to the same warnings about log file placement and security.
Syntax:
Listen [IP-address:]port number
Context: server config
Status: MPM
Module: threaded, perchild, prefork, mpm_winnt
The Listen directive instructs Apache to listen to only specific IP
addresses or ports; by default it responds to requests on all IP
interfaces, but only on the port given by the Port directive.
The Listen 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, instead of the port given by the Port directive. If an IP address is given as well as a port, the server will listen on the given port and interface.
Note that you may still require a Port directive so that URLs that Apache generates that point to your server still work.
Multiple Listen 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 80 Listen 8000To make the server accept connections on two specified interfaces and port numbers, use
Listen 192.170.2.1:80 Listen 192.170.2.5:8000
See Also:
DNS Issues
See Also:
Setting which addresses and ports Apache uses
See Also:
Known Bugs
Syntax: ListenBacklog backlog
Default: ListenBacklog 511
Context: server config
Status: MPM
Module: threaded, perchild, prefork, mpm_winnt
The maximum length of the queue of pending connections. Generally no
tuning is needed or desired, however on some systems it is desirable
to increase this when under a TCP SYN flood attack. See
the backlog parameter to the listen(2) system call.
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.
Syntax: LockFile filename
Default: LockFile logs/accept.lock
Context: server config
Status: MPM
Module: threaded, perchild, prefork
The LockFile directive sets the path to the lockfile used when
Apache is compiled with either USE_FCNTL_SERIALIZED_ACCEPT or
USE_FLOCK_SERIALIZED_ACCEPT. This directive should normally be
left at its default value. The main reason for changing it is if
the logs directory is NFS mounted, since the lockfile
must be stored on a local disk. The PID of the main
server process is automatically appended to the filename.
SECURITY: It is best to avoid putting this file in a
world writable directory such as /var/tmp because someone
could create a denial of service attack and prevent the server from
starting by creating a lockfile with the same name as the one the
server will try to create.
Syntax: MaxClients number
Default: MaxClients 8 (with threads)
MaxClients 256 (no threads)
Context: server config
Status: MPM
Module: threaded, prefork
The MaxClients directive sets the limit on the number of child
processes that will be created to serve requests. When the server is
built without threading, no more than this number of clients can be
served simultaneously. To configure more than 256 clients, you must
edit the HARD_SERVER_LIMIT entry in
mpm_default.h and recompile.
Any connection attempts over the MaxClients limit will normally be queued, up to a number based on the ListenBacklog directive. Once a child process is freed at the end of a different request, the connection will then be serviced.
When the server is compiled with threading, then the maximum number of simultaneous requests that can be served is obtained from the value of this directive multiplied by ThreadsPerChild.
Syntax: MaxRequestsPerChild number
Default: MaxRequestsPerChild 10000
Context: server config
Status: MPM
Module: threaded, prefork, perchild, mpm_winnt
The MaxRequestsPerChild directive sets the limit on the number of requests that an individual child server process will handle. After MaxRequestsPerChild requests, the child process will die. If MaxRequestsPerChild is 0, then the process will never expire.
Setting MaxRequestsPerChild to a non-zero limit has two beneficial effects:
NOTE: For KeepAlive requests, only the first request is counted towards this limit. In effect, it changes the behavior to limit the number of connections per child.
Syntax: MaxSpareThreads number
Default: MaxSpareThreads 10 (Perchild) or 500 (threaded)
Context: server config
Status: core
Module: threaded, perchild
Maximum number of idle threads. Different MPMs deal with this directive differently. Perchild monitor the number of idle threads on a per-child basis. If there are too many idle threads in that child, the server will begin to kill threads within that child.
threaded 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.
See also MinSpareThreads and StartServers.
Syntax: MaxThreadsPerChild number
Default: MaxThreadsPerChild 64
Context: server config
Status: core
Module: threaded, perchild
Maximum number of threads per child. For MPMs with a variable
number of threads per child, this directive sets the maximum number of
threads that will be created in each child process. To increase this
value beyond its default, it is necessary to change the value of
the compile-time define HARD_THREAD_LIMIT and recompile
the server.
Syntax: MinSpareServers number
Default: MaxSpareThreads 5 (Perchild) or 250 (threaded)
Context: server config
Status: core
Module: threaded, perchild
Minimum number of idle threads to handle request spikes. Different MPMs deal with this directive differently. Perchild monitor the number of idle threads on a per-child basis. If there aren't enough idle threads in that child, the server will begin to create new threads within that child.
threaded deals with idle threads on a server-wide basis. If there aren't enough idle threads in the server then child processes are created until the number of idle threads is greater than number.
See also MaxSpareThreads and StartServers.Syntax: NumServers number
Default: NumServers 2
Context: server config
Status: MPM
Module: perchild
Number of children alive at the same time. MPMs that use this directive do not dynamically create new child processes so this number should be large enough to handle the requests for the entire site.
Syntax: ScoreBoardFile filename
Default: ScoreBoardFile logs/apache_status
Context: server config
Status: MPM
Module: threaded, perchild, prefork
The ScoreBoardFile directive is required on some architectures to place a file that the server will use to communicate between its children and the parent. The easiest way to find out if your architecture requires a scoreboard file is to run Apache and see if it creates the file named by the directive. If your architecture requires it then you must ensure that this file is not used at the same time by more than one invocation of Apache.
If you have to use a ScoreBoardFile 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.
See Also: Stopping and Restarting Apache
Syntax: SendBufferSize bytes
Context: server config
Status: MPM
Module: threaded, perchild, prefork, mpm_winnt
Syntax: StartServers number
Default: StartServers 5
Context: server config
Status: MPM
Module: threaded, prefork
The StartServers directive sets the number of child server processes created on startup. As the number of processes is dynamically controlled depending on the load, there is usually little reason to adjust this parameter.
See also MinSpareThreads and MaxSpareThreads.
Syntax: StartThreads number
Default: StartThreads 5
Context: server config
Status: MPM
Module: perchild
Number of threads each child creates on startup. As the number of threads is dynamically controlled depending on the load, there is usually little reason to adjust this parameter.
Syntax: ThreadsPerChild number
Default: ThreadsPerChild 50
Context: server config
Status: MPM
Module: threaded, mpm_winnt
This directive sets the number of threads created by each child process. The child creates these threads at startup and never creates more. if using an MPM like mpmt_winnt, where there is only one child process, this number should be high enough to handle the entire load of the server. If using an MPM like threaded, where there are multiple child processes, the total number of threads should be high enough to handle the common load on the server.
Syntax: User unix-userid
Default: User #-1
Context: server config, virtual host
Status: core
Module: threaded, perchild, prefork
nobody, but this is not always possible or desirable.
For example mod_proxy's cache, when enabled, must be accessible to this user
(see mod_proxy's CacheRoot
directive).Notes: If you start the server as a non-root user, it will fail to change to the lesser privileged user, and will instead continue to run as that original user. If you do start the server as root, then it is normal for the parent process to remain running as root.
Special note: Use of this directive in <VirtualHost> requires a properly configured suEXEC wrapper. When used inside a <VirtualHost> in this manner, only the user that CGIs are run as is affected. Non-CGI requests are still processed with the user specified in the main User directive.
SECURITY: Don't set User (or Group) to
root unless you know exactly what you are doing, and what the
dangers are.