Nginx - HTTP Configuration, Module Directives

Socket and Host Configuration

This set of directives will allow you to configure your virtual hosts. In practice, this materializes by creating server blocks that you identify either by a hostname or by an IP address and port combination. In addition, some directives will let you fine-tune your network settings by configuring TCP socket options.

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listen

Context: server

Specifies the IP address and/or the port to be used by the listening socket that will serve the website. Sites are generally served on port 80 (the default value) via HTTP, or 443 via HTTPS.

Syntax: listen [address][:port] [additional options];

Additional options:

default_server: Specifies that this server block is to be used as the default website for any request received at the specified IP address and port

ssl: Specifies that the website should be served using SSL

Other options are related to the bind and listen system calls: backlog=num, rcvbuf=size, sndbuf=size, accept_filter=filter, deferred, setfib=number, and bind

Examples:

listen 192.168.1.1:80;
listen 127.0.0.1;
listen 80 default;
listen [:::a8c9:1234]:80; # IPv6 addresses must be put between square brackets
listen 443 ssl;

This directive also allows Unix sockets:

listen unix:/tmp/nginx.sock; 

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server_name

Context: server

Assigns one or more hostnames to the server block. When Nginx receives an HTTP request, it matches the Host header of the request against all of the server blocks. The first server block to match this hostname is selected.

Plan B: If no server block matches the desired host, Nginx selects the first server block that matches the parameters of the listen directive (such as listen *:80 would be a catch-all for all requests received on port 80), giving priority to the first block that has the default option enabled on the listen directive.

Note that this directive accepts wildcards as well as regular expressions (in which case, the hostname should start with the ~ character).

Syntax: server_name hostname1 [hostname2…];

Examples:

server_name www.website.com;
server_name www.website.com website.com;
server_name *.website.com;
server_name .website.com; # combines both *.website.com and website.com
server_name *.website.*;
server_name ~^\.example\.com$;

Note that you may use an empty string as the directive value in order to catch all of the requests that do not come with a Host header, but only after at least one regular name (or "_" for a dummy hostname):

server_name website.com "";
server_name _ "";

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server_name_in_redirect

Context: http, server, location

This directive applies the case of internal redirects (for more information about internal redirects, check the Rewrite Module section). If set to on, Nginx will use the first hostname specified in the server_name directive. If set to off, Nginx will use the value of the Host header from the HTTP request. 

Syntax: on or off

Default value: off

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server_names_hash_max_size

Context: http

Nginx uses hash tables for various data collections in order to speed up the processing of requests. This directive defines the maximum size of the server names hash table. The default value should fit with most configurations. If this needs to be changed, Nginx will automatically tell you on startup, or when you reload its configuration.

Syntax: Numeric value

Default value: 512 

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server_names_hash_bucket_size

Context: http

Sets the bucket size for server names hash tables. Similarly, you should only change this value if Nginx tells you to.

Syntax: Numeric value

Default value: 32 (or 64, or 128, depending on your processor cache specifications).

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port_in_redirect

Context: http, server, location

In the case of a redirect, this directive defines whether or not Nginx should append the port number to the redirection URL. 

Syntax: on or off

Default value: on

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tcp_nodelay

Context: http, server, location

Enables or disables the TCP_NODELAY socket option for keep-alive connections only. Quoting the Linux documentation on sockets programming:

"TCP_NODELAY is for a specific purpose; to disable the Nagle buffering algorithm. It should only be set for applications that send frequent small bursts of information without getting an immediate response, where timely delivery of data is required (the canonical example is mouse movements)."

Syntax: on or off

Default value: on

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tcp_nopush

Context: http, server, location

Enables or disables the TCP_NOPUSH (FreeBSD) or TCP_CORK (Linux) socket option. Note that this option only applies if the sendfile directive is enabled. If tcp_nopush is set to on, Nginx will attempt to transmit the entire HTTP response headers in a single TCP packet.

Syntax: on or off

Default value: off

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sendfile

Context: http, server, location

If this directive is enabled, Nginx will use the sendfile kernel call to handle file transmission. If disabled, Nginx will handle the file transfer by itself. Depending on the physical location of the file being transmitted (such as NFS), this option may affect the server performance.

Syntax: on or off

Default value: off

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sendfile_max_chunk

Context: http, server

This directive defines a maximum size of data to be used for each call to sendfile (read above).

Syntax: Numeric value (size)

Default value: 0

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send_lowat

Context: http, server

An option allowing you to make use of the SO_SNDLOWAT flag for TCP sockets under FreeBSD only. This value defines the minimum number of bytes in the buffer for output operations.

Syntax: Numeric value (size)

Default value: 0

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reset_timedout_connection

Context: http, server, location

When a client connection times out, its associated information may remain in memory depending on the state it was on. Enabling this directive will erase all memory associated to the connection after it times out.

Syntax: on or off

Default value: off

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Paths and Documents

This section describes directives that configure the documents that should be served for each website such as the document root, the site index, error pages, and so on.

---

Context: http, server, location, if. Variables are accepted.

Defines the document root, containing the files you wish to serve to your visitors.

Syntax: Directory path

Default value: html

Example:

root /home/website.com/public_html;

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alias

Context: location. Variables are accepted.

alias is a directive that you place in a location block only. It assigns a different path for Nginx to retrieve documents for a specific request. As an example, consider the following configuration:

http {
　　server {
　　　　server_name localhost;
　　　　root /var/www/website.com/html;
　　　　location /admin/ {
　　　　　　alias /var/www/locked/;
　　　　}
　　}
}

When a request for http://localhost/ is received, files are served from the /var/www/website.com/html/ folder. However, if Nginx receives a request for http://localhost/admin/, the path used to retrieve the files is /home/website.com/locked/. Moreover, the value of the document root directive (root) is not altered. This procedure is invisible in the eyes of dynamic scripts.

Syntax: Directory (do not forget the trailing /) or file path

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error_page

Context: http, server, location, if. Variables are accepted.

Allows you to affect URIs to HTTP response code and optionally to substitute the code with another.

Syntax: error_page code1 [code2…] [=replacement code] [=@block | URI]

Examples:

error_page 404 /not_found.html;
error_page 500 501 502 503 504 /server_error.html;
error_page 403 http://website.com/;
error_page 404 @notfound; # jump to a named location block
error_page 404 =200 /index.html; # in case of 404 error, redirect to index.html with a 200 OK response code

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if_modified_since

Context: http, server, location

Defines how Nginx handles the If-Modified-Since HTTP header. This header is mostly used by search engine spiders (such as Google web crawling bots). The robot indicates the date and time of the last pass. If the requested file was not modified since that time the server simply returns a 304 Not Modified response code with no body.

This directive accepts the following three values:

off: Ignores the If-Modified-Since header.

exact: Returns 304 Not Modified if the date and time specified in the HTTP header are an exact match with the actual requested file modification date. If the file modification date is anterior or ulterior, the file is served normally (200 OK response).

before: Returns 304 Not Modified if the date and time specified in the HTTP header is anterior or equal to the requested file modification date.

Syntax: if_modified_since off | exact | before

Default value: exact

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index

Context: http, server, location. Variables are accepted.

Defines the default page that Nginx will serve if no filename is specified in the request (in other words, the index page). You may specify multiple filenames and the first file to be found will be served. If none of the specified files are found, Nginx will either attempt to generate an automatic index of the files, if the autoindex directive is enabled or return a 403 Forbidden error page. Optionally, you may insert an absolute filename (such as /page.html, based from the document root directory) but only as the last argument of the directive.

Syntax: index file1 [file2…] [absolute_file];

Default value: index.html

Example:

index index.php index.html index.htm;
index index.php index2.php /catchall.php;

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recursive_error_pages

Context: http, server, location

Sometimes an error page itself served by the error_page directive may trigger an error, in this case the error_page directive is used again (recursively). This directive enables or disables recursive error pages.

Syntax: on or off

Default value: off

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try_files

Context: server, location. Variables are accepted.

Attempts to serve the specified files (arguments 1 to N-1), if none of these files exist, jumps to the respective named location block (last argument) or serves the specified URI.

Syntax: Multiple file paths, followed by a named location block or a URI

Example:

location / {
　　try_files $uri $uri.html $uri.php $uri.xml @proxy;
}
# the following is a "named location block"
location @proxy {
　　proxy_pass 127.0.0.1:8080;
}

In this example, Nginx tries to serve files normally. If the request URI does not correspond to any existing file, Nginx appends .html to the URI and tries to serve the file again. If it still fails, it tries with .php, then .xml. Eventually, if all of these possibilities fail, another location block (@proxy) handles the request.

You may also specify $uri/ in the list of values in order to test for the existence of a directory with that name.

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Client Requests

This section documents the way that Nginx will handle client requests. Among other things, you are allowed to configure the keep-alive mechanism behavior and possibly logging client requests into files.

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keepalive_requests

Context: http, server, location

Maximum amount of requests served over a single keep-alive connection.

Syntax: Numeric value

Default value: 100

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keepalive_timeout

Context: http, server, location

This directive defines the amount of seconds the server will wait before closing a keep-alive connection. The second (optional) parameter is transmitted as the value of the Keep-Alive: timeout= HTTP response header. The intended effect is to let the client browser close the connection itself after this period has elapsed. Note that some browsers ignore this setting. Internet Explorer, for instance, automatically closes the connection after around 60 seconds.

Syntax: keepalive_timeout time1 [time2];

Default value: 75

Example:

keepalive_timeout 75;
keepalive_timeout 75 60;

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keepalive_disable

Context: http, server, location

This option allows you to disable the keepalive functionality for the browser families of your choice.

Syntax: keepalive_disable browser1 browser2;

Default value: msie6

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send_timeout

Context: http, server, location

The amount of time after which Nginx closes an inactive connection. A connection becomes inactive the moment a client stops transmitting data.

Syntax: Time value (in seconds)

Default value: 60

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client_body_in_file_only

Context: http, server, location

If this directive is enabled, the body of incoming HTTP requests will be stored into actual files on the disk. The client body corresponds to the client HTTP request raw data, minus the headers (in other words, the content transmitted in POST requests). Files are stored as plain text documents.

This directive accepts three values:

• off: Do not store the request body in a file
• clean: Store the request body in a file and remove the file after a request is processed
• on: Store the request body in a file, but do not remove the file after the request is processed (not recommended unless for debugging purposes)

Syntax: client_body_in_file_only on | clean | off

Default value: off

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client_body_in_single_buffer

Context: http, server, location

Defines whether or not Nginx should store the request body in a single buffer in memory.

Syntax: on or off

Default value: off

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client_body_buffer_size

Context: http, server, location

Specifies the size of the buffer holding the body of client requests. If this size is exceeded, the body (or at least part of it) will be written to the disk. Note that if the client_body_in_file_only directive is enabled, request bodies are always stored to a file on the disk, regardless of their size (whether they fit in the buffer or not).

Syntax: Size value

Default value: 8k or 16k (2 memory pages) depending on your computer architecture

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client_body_temp_path

Context: http, server, location

Allows you to define the path of the directory that will store the client request body files. An additional option lets you separate those files into a folder hierarchy over up to three levels.

Syntax: client_body_temp_path path [level1] [level2] [level3]

Default value: client_body_temp

client_body_temp_path /tmp/nginx_rbf;
client_body_temp_path temp 2; # Nginx will create 2-digit folders to hold request body files
client_body_temp_path temp 1 2 4; # Nginx will create 3 levels of folders (first level: 1 digit, second level: 2 digits, third level: 4 digits)

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client_body_timeout

Context: http, server, location

Defines the inactivity timeout while reading a client request body. A connection becomes inactive the moment the client stops transmitting data. If the delay is reached, Nginx returns a 408 Request timeout HTTP error.

Syntax: Time value (in seconds)

Default value: 60

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client_header_buffer_size

Context: http, server, location

This directive allows you to define the size of the buffer that Nginx allocates to request headers. Usually, 1k is enough. However, in some cases, the headers contain large chunks of cookie data or the request URI is lengthy. If that is the case, then Nginx allocates one or more larger buffers (the size of larger buffers is defined by the large_client_header_buffers directive).

Syntax: Size value

Default value: 1k

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client_header_timeout

Context: http, server, location

Defines the inactivity timeout while reading a client request header. A connection becomes inactive the moment the client stops transmitting data. If the delay is reached, Nginx returns a 408 Request timeout HTTP error.

Syntax: Time value (in seconds)

Default value: 60

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client_max_body_size

Context: http, server, location

It is the maximum size of a client request body. If this size is exceeded, Nginx returns a 413 Request entity too large HTTP error. This setting is particularly important if you are going to allow users to upload files to your server over HTTP.

Syntax: Size value

Default value: 1m

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large_client_header_buffers

Context: http, server, location

Defines the amount and size of larger buffers to be used for storing client requests, in case the default buffer (client_header_buffer_size) was insufficient. Each line of the header must fit in the size of a single buffer. If the request URI line is greater than the size of a single buffer, Nginx returns the 414 Request URI too large error. If another header line exceeds the size of a single buffer, Nginx returns a 400 Bad request error.

Syntax: large_client_header_buffers amount size

Default value: 4*8 kilobytes

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lingering_time

Context: http, server, location

This directive applies to client requests with a request body. As soon as the amount of uploaded data exceeds max_client_body_size, Nginx immediately sends a 413 Request entity too large HTTP error response. However, most browsers continue uploading data regardless of that notification. This directive defines the amount of time Nginx should wait after sending this error response before closing the connection.

Syntax: Numeric value (time)

Default value: 30 seconds

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lingering_timeout

Context: http, server, location

This directive defines the amount of time that Nginx should wait between two read operations before closing the client connection.

Syntax: Numeric value (time)

Default value: 5 seconds

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lingering_close

Context: http, server, location

Controls the way Nginx closes client connections. Set this to off to immediately close connections after all of the request data has been received. The default value (on) allows to wait and process additional data if necessary. If set to always, Nginx will always wait to close the connection. The amount of waiting time is defined by the lingering_timeout directive.

Syntax: on, off, or always

Default value: on

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ignore_invalid_headers

Context: http, server

If this directive is disabled, Nginx returns a 400 Bad Request HTTP error in case request headers are malformed.

Syntax: on or off

Default value: on

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chunked_transfer_encoding

Context: http, server, location

Enables or disables chunked transfer encoding for HTTP 1.1 requests.

Syntax: on or off

Default value: on

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max_ranges

Context: http, server, location

Defines how many byte ranges Nginx will accept to serve when a client requests partial content from a file. If you do not specify a value, there is no limit. If you set this to 0, the byte range functionality is disabled.

Syntax: Size value

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MIME types

Nginx offers two particular directives that will help you configure MIME types: types and default_type, which defines the default MIME types for documents. This will affect the Content-Type HTTP header sent within responses. Read on.

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types

Context: http, server, location

This directive allows you to establish correlations between MIME types and file extensions. It's actually a block accepting a particular syntax:

types {
　　mimetype1 extension1;
　　mimetype2 extension2 [extension3…];
　　[…]
}

When Nginx serves a file, it checks the file extension in order to determine the MIME type. The MIME type is then sent as the value of the Content-Type HTTP header in the response. This header may affect the way browsers handle files. For example, if the MIME type of the file you are requesting is application/pdf, your browser may, for instance, attempt to render the file using a plugin associated to that MIME type instead of merely downloading it.

Nginx includes a basic set of MIME types as a standalone file (mime.types) to be included with the include directive:

include mime.types;

This file already covers the most important file extensions so you will probably not need to edit it. If the extension of the served file is not found within the listed types, the default type is used, as defined by the default_type directive (read below).

Note that you may override the list of types by re-declaring the types block. A useful example would be to force all files in a folder to be downloaded instead of being displayed:

http {
　　include mime.types;
　　[…]
　　location /downloads/ {
　　　　# removes all MIME types
　　　　types { }
　　　　default_type application/octet-stream;
　　}
　　[…]
}

Note that some browsers ignore MIME types and may still display files if their filename ends with a known extension, such as .html or .txt.

The default values, if the mime.types file is not included, are:

types {
　　text/html html;
　　image/gif gif;
　　image/jpeg jpg;
}

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default_type

Context: http, server, location
Defines the default MIME type. When Nginx serves a file, the file extension is matched against the known types declared within the types block in order to return the proper MIME type as value of the Content-Type HTTP response header. If the extension doesn't match any of the known MIME types, the value of the default_type directive is used.

Syntax: MIME type

Default value: text/plain

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types_hash_max_size

Context: http, server, location

Defines the maximum size of an entry in the MIME types hash table.

Syntax: Numeric value.

Default value: 4 k or 8 k (1 line of CPU cache)

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Limits and Restrictions

This set of directives will allow you to add restrictions that apply when a client attempts to access a particular location or document on your server.

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imit_except

Context: location

This directive allows you to prevent the use of all HTTP methods, except the ones that you explicitly allow. Within a location block, you may want to restrict the use of some HTTP methods, such as forbidding clients from sending POST requests. You need to define two elements — first, the methods that are not forbidden (the allowed methods; all others will be forbidden), and second, the audience that is affected by the restriction:

location /admin/ {
　　limit_except GET {
　　　　allow 192.168.1.0/24;
　　　　deny all;
　　}
}

This example applies a restriction to the /admin/ location — all visitors are only allowed to use the GET method. Visitors that have a local IP address, as specified with the allow directive, are not affected by this restriction. If a visitor uses a forbidden method, Nginx will return in a 403 Forbidden HTTP error. Note that the GET method implies the HEAD method (if you allow GET, both GET and HEAD are allowed).

The syntax is particular:

limit_except METHOD1 [METHOD2…] {
　　allow | deny | auth_basic | auth_basic_user_file | proxy_pass | perl;
}

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limit_rate

Context: http, server, location, if

Allows you to limit the transfer rate of individual client connections. The rate is expressed in bytes per second:

limit_rate 500k;

This will limit connection transfer rates to 500 kilobytes per second. If a client opens two connections, the client will be allowed 2 * 500 kilobytes.

Syntax: Size value

Default value: No limit

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limit_rate_after

Context: http, server, location, if

Defines the amount of data transferred before the limit_rate directive takes effect.

limit_rate_after 10m;

Nginx will send the first 10 megabytes at maximum speed. Past this size, the transfer rate is limited by the value specified with the limit_rate directive (see above). Similar to the limit_rate directive, this setting only applies to a single connection.

Syntax: Size value

Default: None

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satisfy

Context: location

The satisfy directive defines whether clients require all access conditions to be valid (satisfy all) or at least one (satisfy any).

location /admin/ {
　　allow 192.168.1.0/24;
　　deny all;
　　auth_basic "Authentication required";
　　auth_basic_user_file conf/htpasswd;
}

In the previous example, there are two conditions for clients to be able to access the resource:

• Through the allow and deny directives, we only allow clients that have a local IP address, all other clients are denied access
• Through the auth_basic and auth_basic_user_file directives, we only allow clients that provide a valid username and password

With satisfy all, the client must satisfy both conditions in order to gain access to the resource. With satisfy any, if the client satisfies either condition, they are granted access.

Syntax: satisfy any | all

Default value: all

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internal

Context: location

This directive specifies that the location block is internal. In other words, the specified resource cannot be accessed by external requests.

server {
　　[…]
　　server_name .website.com;
　　location /admin/ {
　　　　internal;
　　}
}

With the previous configuration, clients will not be able to browse http://website. com/admin/. Such requests will be met with 404 Not Found errors. The only way to access the resource is via internal redirects (check the Rewrite Module section for more information on internal redirects).

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File processing and caching

It's important for your websites to be built upon solid foundations. File access and caching is a critical aspect of web serving. In this perspective, Nginx lets you perform precise tweaking with the use of the following directives.

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disable_symlinks

This directive allows you to control the way Nginx handles symbolic links when they are to be served. By default (directive value is off) symbolic links are allowed and Nginx follows them. You may decide to disable the following of symbolic links under different conditions by specifying one of these values:

• on: If any part of the requested URI is a symbolic link, access to it is denied and Nginx returns a 403 Forbidden HTTP error page.
• if_not_owner: Similar to the above, but access is denied only if the link and the object it points to have different owners.

• The optional parameter from= allows you to specify a part of the URL that will not be checked for symbolic links. For example, disable_symlinks on from=$document_root will tell Nginx to normally follow symbolic links in the URI up to the $document_root folder. If a symbolic link is found in the URI parts after that, access to the requested file will be denied.

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directio

Context: http, server, location

If this directive is enabled, files with a size greater than the specified value will be read with the Direct I/O system mechanism. This allows Nginx to read data from the storage device and place it directly in memory with no intermediary caching process involved.

Syntax: Size value, or off

Default value: off

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directio_alignment

Context: http, server, location

Sets byte alignment when using directio. Set this value to 4k if you use XFS under Linux.

Syntax: Size value

Default value: 512

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open_file_cache

Context: http, server, location

This directive allows you to enable the cache which stores information about open files. It does not actually store file contents itself but only information such as:

• File descriptors (file size, modification time, and so on).
• The existence of files and directories.
• File errors, such as Permission denied, File not found, and so on. Note that this can be disabled with the open_file_cache_errors directive.

This directive accepts two arguments:

• max=X, where X is the amount of entries that the cache can store. If this amount is reached, older entries will be deleted in order to leave room for newer entries.
• Optionally inactive=Y, where Y is the amount of seconds that a cache entry should be stored. By default, Nginx will wait 60 seconds before clearing a cache entry. If the cache entry is accessed, the timer is reset. If the cache entry is accessed more than the value defined by open_file_cache_min_uses, the cache entry will not be cleared (until Nginx runs out of space and decides to clear out older entries).

Syntax: open_file_cache max=X [inactive=Y] | off

Default value: off

Example:

open_file_cache max=5000 inactive=180;

---

open_file_cache_errors

Context: http, server, location

Enables or disables the caching of file errors with the open_file_cache directive (read above).

Syntax: on or off

Default value: off

---

open_file_cache_min_uses

Context: http, server, location

By default, entries in the open_file_cache are cleared after a period of inactivity (60 seconds, by default). If there is activity though, you can prevent Nginx from removing the cache entry. This directive defines the amount of time an entry must be accessed in order to be eligible for protection.

open_file_cache_min_uses 3;

If the cache entry is accessed more than three times, it becomes permanently active and is not removed until Nginx decides to clear out older entries to free up some space.

Syntax: Numeric value

Default value: 1

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open_file_cache_valid

Context: http, server, location

The open file cache mechanism is important, but cached information quickly becomes obsolete especially in the case of a fast-moving filesystem. In that perspective, information needs to be re-verified after a short period of time. This directive specifies the amount of seconds that Nginx will wait before revalidating a cache entry.

Syntax: Time value (in seconds)

Default value: 60

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read_ahead

Context: http, server, location

Defines the amount of bytes to pre-read from files. Under Linux-based operating systems, setting this directive to a value above 0 will enable reading ahead, but the actual value you specify has no effect. Set this to 0 to disable pre-reading.

Syntax: Size value

Default value: 0

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Other directives

The following directives relate to various aspects of the web server — logging, URI composition, DNS, and so on.

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log_not_found

Context: http, server, location

Enables or disables logging of 404 Not Found HTTP errors. If your logs get filled with 404 errors due to missing favicon.ico or robots.txt files, you might want to turn this off.

Syntax: on or off

Default value: on

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log_subrequest

Context: http, server, location

Enables or disables logging of sub-requests triggered by internal redirects or SSI requests.

Syntax: on or off

Default value: off

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merge_slashes

Context: http, server, location

Enabling this directive will have the effect of merging multiple consecutive slashes in a URI. It turns out to be particularly useful in situations resembling the following:

server {
　　[…]
　　server_name website.com;
　　location /documents/ {
　　　　type { }
　　　　default_type text/plain;
　　}
}

By default, if the client attempts to access http://website.com//documents/ (note the // in the middle of the URI), Nginx will return a 404 Not found HTTP error. If you enable this directive, the two slashes will be merged into one and the location pattern will be matched.

Syntax: on or off

Default value: off

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msie_padding

Context: http, server, location

This directive functions with the Microsoft Internet Explorer (MSIE) and Google Chrome browser families. In the case of error pages (with error code 400 or higher), if the length of the response body is less than 512 bytes, these browsers will display their own error page, sometimes at the expense of a more informative page provided by the server. If you enable this option, the body of responses with a status code of 400 or higher will be padded to 512 bytes.

Syntax: on or off

Default value: off

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msie_refresh

Context: http, server, location

It is another MSIE-specific directive that will take effect in the case of HTTP response codes 301 Moved permanently and 302 Moved temporarily. When enabled, Nginx sends clients running an MSIE browser a response body containing a refresh meta tag (<meta http-equiv="Refresh"…>) in order to redirect the browser to the new location of the requested resource.

Syntax: on or off

Default value: off

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resolver

Context: http, server, location

Specifies the name servers that should be employed by Nginx to resolve hostnames to IP addresses and vice-versa. DNS query results are cached for some time, either by respecting the TTL provided by the DNS server, or by specifying a time value to the valid argument.

Syntax: IP addresses, valid=Time value

Default value: None (system default)

Example:

resolver 127.0.0.1; # use local DNS
resolver 8.8.8.8 8.8.4.4 valid=1h; # use Google DNS and cache results for 1 hour

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resolver_timeout

Context: http, server, location

Timeout for a hostname resolution query.

Syntax: Time value (in seconds)

Default value: 30

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server_tokens

Context: http, server, location

This directive allows you to define whether or not Nginx should inform the clients of the running version number. There are two situations where Nginx indicates its version number:

• In the server header of HTTP responses (such as nginx/1.2.9). If you set server_tokens to off, the server header will only indicate Nginx.
• On error pages, Nginx indicates the version number in the footer. If you set server_tokens to off, the footer of error pages will only indicate Nginx.

If you are running an older version of Nginx and do not plan to update it, it might be a good idea to hide your version number for security reasons.

Syntax: on or off

Default value: on

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underscores_in_headers

Context: http, server

Allows or disallows underscores in custom HTTP header names. If this directive is set to on, the following example header is considered valid by Nginx: test_header: value.

Syntax: on or off

Default value: off

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variables_hash_max_size

Context: http

This directive defines the maximum size of the variables hash tables. If your server configuration uses a total of more than 512 variables, you will have to increase this value.

Syntax: Numeric value

Default value: 512

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variables_hash_bucket_size

Context: http

This directive allows you to set the bucket size for the variables hash tables.

Syntax: Numeric value

Default value: 64 (or 32, or 128, depending on your processor cache specifications)

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post_action

Context: http, server, location, if

Defines a post-completion action, a URI that will be called by Nginx after the request has been completed.

Syntax: URI or named location block.

Example:

location /payment/ {
　　post_action /scripts/done.php;
}

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