About this book

Nginx is a lightweight HTTP server designed for high-traffic websites, with network scalability as the primary objective. With the advent of high speed Internet access, short loading times and fast transfer rates have become a necessity. This free, open source solution will either come as a full replacement of other software such as Apache, or stand in front of your existing infrastructure to improve its overall speed.

"Nginx HTTP Server - Second Edition" provides a detailed guide to setting up Nginx in different ways that correspond to actual production situations: as a standalone server, as a reverse proxy, interacting with applications via FastCGI and more. In addition, the complete directive reference will be your best friend at all stages of the configuration and maintenance processes.

This book is the perfect companion for both Nginx beginners and experienced administrators. For beginners, it will take you through the complete process of setting up this lightweight HTTP server on your system and configuring its various modules to get it to do exactly what you need, in a fast and secure way. For more experienced administrators, this book provides different angles of approach that can help you make the most of your current infrastructure. Nginx can be employed in many situations, whether you are looking to construct an entirely new web-serving architecture or simply want to integrate an efficient tool to optimize your site loading speeds.

This book takes you through the setup and configuration of Nginx by detailing every step of the way, from downloading to configuring your server in a selection of common architectures.

Publication date:
July 2013
Publisher
Packt
Pages
318
ISBN
9781782162322

 

Chapter 1. Downloading and Installing Nginx

In this first chapter, we will proceed with the necessary steps towards establishing a functional setup of Nginx. This moment is crucial for the smooth functioning of your web server—there are some required libraries and tools for installing the web server, some parameters that you will have to decide upon when compiling the binaries, and there may also be some configuration changes to perform on your system.

This chapter covers the following:

  • Downloading and installing the prerequisites for compiling the Nginx binaries

  • Downloading a suitable version of the Nginx source code

  • Configuring Nginx compile-time options

  • Controlling the application with an init script

  • Configuring the system to launch Nginx automatically on startup

 

Setting up the prerequisites


As you can see, we have chosen to download the source code of the application and compile it manually, as opposed to installing it using a package manager, such as Yum, Aptitude, or Yast. There are two reasons behind this choice. First, the package may not be available in the enabled repositories of your Linux distribution. On top of that, the rare repositories that offer to download and install Nginx automatically mostly contain outdated versions. More importantly, there is the fact that we need to configure a variety of significant compile-time options. As a result of this choice, your system will require some tools and libraries for the compilation process.

Depending on the optional modules that you select at compile time, you will perhaps need different prerequisites. We will guide you through the process of installing the most common ones, such as GCC, PCRE, zlib, and OpenSSL.

Note

If your operating system offers the possibility to install the Nginx package from a repository, and you are confident enough that the available version will suit all of your needs with the modules included by default, you could consider skipping this chapter altogether and simply run one the following commands. We still recommend getting the latest version and building it from source seeing as it contains the latest bug fixes and security patches. For a Debian-based operating system:

apt-get install nginx

For Red Hat-based operating systems:

yum install nginx

GCC – GNU Compiler Collection

Nginx is a program written in C, so you will first need to install a compiler tool such as the GNU Compiler Collection (GCC) on your system. GCC may already be present on your system, but if that is not the case you will have to install it before going any further.

Note

GCC is a collection of free open source compilers for various languages—C, C++, Java, Ada, FORTRAN, and so on. It is the most commonly used compiler suite in the Linux world, and Windows versions are also available. A vast amount of processors are supported, such as x86, AMD64, PowerPC, ARM, MIPS, and more.

First, make sure it isn't already installed on your system:

If you get the following output, it means that GCC is correctly installed on your system and you can skip to the next section:

gcc: no input files

If you receive the following message, you will have to proceed with the installation of the compiler:

~bash: gcc: command not found

GCC can be installed using the default repositories of your package manager. Depending on your distribution, the package manager will vary—yum for a Red Hat-based distribution, apt for Debian and Ubuntu, yast for SuSE Linux, and so on. Here is the typical way to proceed with the download and installation of the GCC package:

[[email protected] ~]# yum groupinstall "Development Tools"

If you use apt-get:

[[email protected] ~]# apt-get install build-essentials

If you use another package manager with a different syntax, you will probably find the documentation with the man utility. Either way, your package manager should be able to download and install GCC correctly, after having solved the dependencies automatically. Note that this command will not only install GCC, it also proceeds with downloading and installing all common requirements for building applications from source, such as code headers and other compilation tools.

The PCRE library

The Perl Compatible Regular Expression (PCRE) library is required for compiling Nginx. The Rewrite and HTTP Core modules of Nginx use PCRE for the syntax of their regular expressions, as we will discover in later chapters. You will need to install two packages—pcre and pcre-devel. The first one provides the compiled version of the library, whereas the second one provides development headers and source for compiling projects, which are required in our case.

Here are example commands that you can run in order to install both the packages.

Using yum:

[[email protected] ~]# yum install pcre pcre-devel

Or you can install all of the PCRE-related packages:

[[email protected] ~]# yum install pcre*

If you use apt-get:

[[email protected] ~]# apt-get install libpcre3 libpcre3-dev

If these packages are already installed on your system, you will receive a message saying something like Nothing to do, in other words, the package manager did not install or update any component:

Note

Both components are already present on the system.

The zlib library

The zlib library provides developers with compression algorithms. It is required for the use of gzip compression in various modules of Nginx. Again, you can use your package manager to install this component as it is part of the default repositories. Similar to PCRE, you will need both the library and its source—zlib and zlib-devel

Using yum:

[[email protected] ~]# yum install zlib zlib-devel

Using apt-get:

[[email protected] ~]# apt-get install zlib1g zlib1g-dev

These packages install quickly and have no known dependency issues.

OpenSSL

The OpenSSL project is a collaborative effort to develop a robust, commercial-grade, full-featured, and open source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library. The project is managed by a worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation. For more information, visit http://www.openssl.org

The OpenSSL library will be used by Nginx to serve secure web pages. We thus need to install the library and its development package. The process remains the same here—you install openssl and openssl-devel:

[[email protected] ~]# yum install openssl openssl-devel

Using apt-get:

[[email protected] ~]# apt-get install openssl openssl-dev

Note

Please be aware of the laws and regulations in your own country. Some countries do not allow usage of a strong cryptography. The author, publisher, and the developers of the OpenSSL and Nginx projects will not be held liable for any violations or law infringements on your part.

Now that you have installed all of the prerequisites, you are ready to download and compile the Nginx source code.

 

Downloading Nginx


This approach to the download process will lead us to discover the various resources at the disposal of server administrators—websites, communities, and wikis all relating to Nginx. We will also quickly discuss the different version branches available to you, and eventually select the most appropriate one for your setup.

Websites and resources

Although Nginx is a relatively new and growing project, there are already a good number of resources available on the World Wide Web (WWW) and an active community of administrators and developers.

The official website, which is at www.nginx.org, looks rather bare and does not provide a tremendous amount of information or documentation, other than links for downloading the latest versions. On the contrary, you will find a lot of interesting documentation and examples on the official wiki, wiki.nginx.org, seen below:

The wiki provides a large variety of documentation and configuration examples, and it may prove very useful to you in many situations. Moreover, it can be edited by its (registered) users, which is a great help towards keeping the documentation up-to-date. If you have specific questions though, you might as well use the forums—forum.nginx.org. An active community of users will answer your questions in no time. Additionally, the Nginx mailing list, which is relayed on the Nginx forum, will also prove to be an excellent resource for any question you may have. And if you need direct assistance, there is always a bunch of regulars helping each other out on the IRC channel #Nginx on irc.freenode.net.

Another interesting source of information—the blogosphere. A simple query on your favorite search engine should return a good amount of blog articles documenting Nginx, its configuration, and modules.

Personal websites and blogs documenting Nginx

It's now time to head over to the official website and get started with downloading the source code for compiling and installing Nginx. Before you do so, let us have a quick summary of the available versions and the features that come with them.

Version branches

Igor Sysoev, a talented Russian developer and server administrator, initiated this open source project back in 2002. Between the first release in 2004 and the current version, the market share of Nginx has been growing steadily. It now serves over 15 percent of websites on the Internet, according to a May 2013 Netcraft.com survey. The features are plenty and render the application both powerful and flexible at the same time.

There are currently three version branches on the project:

  • Stable version: This version is usually recommended, as it is approved by both developers and users, but is usually a little behind the development version.

  • Development version: This is the latest version available for download. Although it is generally solid enough to be installed on production servers, you may run into the occasional bug. As such, the stable version is recommended, even though you do not get to use the latest features.

  • Legacy version: If, for some reason, you are interested in looking at the older versions, you will find several of them.

A recurrent question regarding development versions is "are they stable enough to be used on production servers?" Cliff Wells, founder and maintainer of the nginx.org wiki website and community, believes so—"I generally use and recommend the latest development version. It's only bit me once!" Early adopters rarely report critical problems. It is up to you to select the version you will be using on your server, knowing that the instructions given in this book should be valid regardless of the release as the Nginx developers have decided to maintain overall backwards compatibility in new versions. You can find more information on version changes, new additions, and bug fixes in the dedicated change log page on the official website.

Features

As of the stable version 1.2.9, Nginx offers an impressive variety of features, which, contrary to what the title of this book indicates, are not all related to serving HTTP content. Here is a list of the main features of the web branch, quoted from the official website www.nginx.org:

  • Handling of static files, index files, and autoindexing; open file descriptor cache.

  • Accelerated reverse proxying with caching; simple load balancing and fault tolerance.

  • Accelerated support with caching of remote FastCGI servers; simple load balancing and fault tolerance.

  • Modular architecture. Filters include Gzipping, byte ranges, chunked responses, XSLT, SSI, and image resizing filter. Multiple SSI inclusions within a single page can be processed in parallel if they are handled by FastCGI or proxied servers.

  • SSL and TLS SNI support (TLS with Server Name Indication (SNI), required for using TLS on a server doing virtual hosting).

Nginx can also be used as a mail proxy server, although this aspect is not closely documented in the book:

  • User redirection to IMAP/POP3 backend using an external HTTP authentication server

  • User authentication using an external HTTP authentication server and connection redirection to an internal SMTP backend

  • Authentication methods:

    • POP3: USER/PASS, APOP, AUTH LOGIN/PLAIN/CRAM-MD5

    • IMAP: LOGIN, AUTH LOGIN/PLAIN/CRAM-MD5

    • SMTP: AUTH LOGIN/PLAIN/CRAM-MD5

  • SSL support

  • STARTTLS and STLS support

Nginx is compatible with many computer architectures and operating systems such as Windows, Linux, Mac OS, FreeBSD, and Solaris. The application runs fine on 32- and 64-bit architectures.

Downloading and extracting

Once you have made your choice as to which version you will be using, head over to www.nginx.org and find the URL of the file you wish to download. Position yourself in your home directory, which will contain the source code to be compiled, and download the file using wget:

[[email protected] ~]$ mkdir src && cd src
[[email protected] src]$ wget http://nginx.org/download/nginx-1.2.9.tar.gz

We will be using version 1.2.9, the latest stable version as of April, 2013. Once downloaded, extract the archive contents in the current folder:

[[email protected] src]$ tar zxf nginx-1.2.9.tar.gz

You have successfully downloaded and extracted Nginx. Now, the next step will be to configure the compilation process in order to obtain a binary that perfectly fits your operating system.

 

Configure options


There are usually three steps when building an application from source—the configuration, the compilation, and the installation. The configuration step allows you to select a number of options that will not be editable after the program is built, as it has a direct impact on the project binaries. Consequently, it is a very important stage that you need to follow carefully if you want to avoid surprises later, such as the lack of a specific module or files being located in a random folder.

The process consists of appending certain switches to the configure script that comes with the source code. We will discover the three types of switches that you can activate; but let us first study the easiest way to proceed.

The easy way

If, for some reason, you do not want to bother with the configuration step, such as for testing purposes or simply because you will be recompiling the application in the future, you may simply use the configure command with no switches. Execute the following three commands to build and install a working version of Nginx:

[[email protected] nginx-1.2.9]# ./configure

Running this command should initiate a long procedure of verifications to ensure that your system contains all of the necessary components. If the configuration process fails, please make sure to check the prerequisites section again, as it is the most common cause of errors. For information about why the command failed, you may also refer to the objs/autoconf.err file, which provides a more detailed report:

[[email protected] nginx-1.2.9]# make

The make command will compile the application. This step should not cause any errors as long as the configuration went fine:

[[email protected] nginx-1.2.9]# make install

This last step will copy the compiled files as well as other resources to the installation directory, by default, /usr/local/nginx. You may need to be logged in as root to perform this operation depending on permissions granted to the /usr/local directory.

Again, if you build the application without configuring it, you take the risk to miss out on a lot of features, such as the optional modules and others that we are about to discover.

Path options

When running the configure command, you are offered the possibility to enable some switches that let you specify the directory or file paths for a variety of elements. Please note that the options offered by the configuration switches may change according to the version you downloaded. The options listed below are valid with the stable version, release 1.2.9. If you use another version, run the configure --help command to list the available switches for your setup.

Using a switch typically consists of appending some text to the command line. For instance, using the --conf-path switch:

[[email protected] nginx-1.2.9]# ./configure --conf-path=/etc/nginx/nginx.conf

Here is an exhaustive list of the configuration switches for configuring paths:

Switch

Usage

Default Value

--prefix=…

The base folder in which Nginx will be installed.

/usr/local/nginx.

Note: If you configure other switches using relative paths, they will connect to the base folder.

For example: Specifying --conf-path=conf/nginx.conf will result in your configuration file being found at /usr/local/nginx/conf/nginx.conf.

--sbin-path=…

The path where the Nginx binary file should be installed.

<prefix>/sbin/nginx.

--conf-path=…

The path of the main configuration file.

<prefix>/conf/nginx.conf.

--error-log-path=…

The location of your error log. Error logs can be configured very accurately in the configuration files. This path only applies in case you do not specify any error logging directive in your configuration.

<prefix>/logs/error.log.

--pid-path=…

The path of the Nginx pid file. You can specify the pid file path in the configuration file. If that's not the case, the value you specify for this switch will be used.

<prefix>/logs/nginx.pid.

Note: The pid file is a simple text file containing the process identifier. It is placed in a well-defined location so that other applications can easily find the pid of a running program.

--lock-path=…

The location of the lock file. Again, it can be specified in the configuration file, but if it isn't, this value will be used.

<prefix>/logs/nginx.lock.

Note: The lock file allows other applications to determine whether or not the program is running. In the case of Nginx, it is used to make sure that the process is not started twice.

--with-perl_modules_path=…

Defines the path to the Perl modules. This switch must be defined if you want to include additional Perl modules.

 

--with-perl=…

Path to the Perl binary file; used for executing Perl scripts. This path must be set if you want to allow execution of Perl scripts.

 

--http-log-path=…

Defines the location of the access logs. This path is used only if the access log directive is unspecified in the configuration files.

<prefix>/logs/access.log.

--http-client-body-temp-path=…

Directory used for storing temporary files generated by client requests.

<prefix>/client_body_temp.

--http-proxy-temp-path=…

Location of the temporary files used by the proxy.

<prefix>/proxy_temp.

--http-fastcgi-temp-path=…

--http-uwsgi-temp-path=…

--http-scgi-temp-path=…

Location of the temporary files used by the HTTP FastCGI, uWSGI, and SCI modules.

Respectively <prefix>/fastcgi_temp,

<prefix>/uwsgi_temp, and <prefix>/scgi_temp.

--builddir=…

Location of the application build.

 

Prerequisites options

Prerequisites come in the form of libraries and binaries. You should by now have them all installed on your system. Yet, even though they are present on your system, there may be occasions where the configuration script cannot locate them. The reasons might be diverse, for example, if they were installed in non-standard directories. In order to solve such problems, you are given the option to specify the path of prerequisites using the following switches. Miscellaneous prerequisite-related options are grouped together.

Compiler options

--with-cc=…

Specifies an alternate location for the C compiler.

--with-cpp=…

Specifies an alternate location for the C preprocessor.

--with-cc-opt=…

Defines additional options to be passed to the C compiler command line.

--with-ld-opt=…

Defines additional options to be passed to the C linker command line.

--with-cpu-opt=…

Specifies a different target processor architecture, among the following values: pentium, pentiumpro, pentium3, pentium4, athlon, opteron, sparc32, sparc64, and ppc64.

PCRE options

--without-pcre

Disables usage of the PCRE library. This setting is not recommended, as it will remove support for regular expressions, consequently disabling the Rewrite module.

--with-pcre

Forces usage of the PCRE library.

--with-pcre=…

Allows you to specify the path of the PCRE library source code.

--with-pcre-opt=…

Additional options for building the PCRE library.

--with-pcre-jit=…

Build PCRE with JIT compilation support.

MD5 options

--with-md5=…

Specifies the path to the MD5 library sources.

--with-md5-opt=…

Additional options for building the MD5 library.

--with-md5-asm

Uses assembler sources for the MD5 library.

SHA1 options

--with-sha1=…

Specifies the path to the SHA1 library sources.

--with-sha1-opt=…

Additional options for building the SHA1 library.

--with-sha1-asm

Uses assembler sources for the SHA1 library.

zlib options

--with-zlib=…

Specifies the path to the zlib library sources.

--with-zlib-opt=…

Additional options for building the zlib library.

--with-zlib-asm=…

Uses assembler optimizations for the following target architectures: pentium, pentiumpro.

OpenSSL options

--with-openssl=…

Specifies the path of the OpenSSL library sources.

--with-openssl-opt=…

Additional options for building the OpenSSL library.

Libatomic

--with-libatomic=…

Forces usage of the libatomic_ops library on systems other than x86, amd64, and sparc. This library allows Nginx to perform atomic operations directly instead of resorting to lock files. Depending on your system, it may result in a decrease in SEGFAULT errors and possibly higher request serving rate.

--with-libatomic=…

Specifies the path of the Libatomic library sources.

Module options

Modules, which will be detailed in Chapter 3, HTTP Configuration, and further, need to be selected before compiling the application. Some are enabled by default and some need to be enabled manually, as you will see in the following table. Please note that an exhaustive and more detailed list of modules can be found in Appendix B, Module Reference.

Modules enabled by default

The following switches allow you to disable modules that are enabled by default:

Modules enabled by default

Description

--without-http_charset_module

Disables the Charset module for re-encoding web pages.

--without-http_gzip_module

Disables the Gzip compression module.

--without-http_ssi_module

Disables the Server Side Include module.

--without-http_userid_module

Disables the User ID module providing user identification via cookies.

--without-http_access_module

Disables the Access module allowing access configuration for IP address ranges.

--without-http_auth_basic_module

Disables the Basic Authentication module.

--without-http_autoindex_module

Disables the Automatic Index module.

--without-http_geo_module

Disables the Geo module allowing you to define variables depending on IP address ranges.

--without-http_map_module

Disables the Map module that allows you to declare map blocks.

--without-http_referer_module

Disables the Referer control module.

--without-http_rewrite_module

Disables the Rewrite module.

--without-http_proxy_module

Disables the Proxy module for transferring requests to other servers.

--without-http_fastcgi_module

--without-http_uwsgi_module

--without-http_scgi_module

Disables the FastCGI, uWSGI, or SCGI modules for interacting with respectively FastCGI, uWSGI, or SCGI processes.

--without-http_memcached_module

Disables the Memcached module for interacting with the memcache daemon.

--without-http_limit_conn_module

Disables the Limit Connections module for restricting resource usage according to defined zones.

--without-http_limit_req_module

Disables the Limit Requests module allowing you to limit the amount of requests per user.

--without-http_empty_gif_module

Disables the Empty Gif module for serving a blank GIF image from memory.

--without-http_browser_module

Disables the Browser module for interpreting the User Agent string.

--without-http_upstream_ip_hash_module

Disables the Upstream module for configuring load-balanced architectures.

--without-http_upstream_least_conn_module

Disables the Least Connections feature

Modules disabled by default

The following switches allow you to enable modules that are disabled by default:

Modules disabled by default

Description

--with-http_ssl_module

Enables the SSL module for serving pages using HTTPS.

--with-http_realip_module

Enables the Real IP module for reading the real IP address from the request header data.

--with-http_addition_module

Enables the Addition module which lets you append or prepend data to the response body.

--with-http_xslt_module

Enables the XSLT module for applying XSL transformations to XML documents.

Note: You will need to install the libxml2 and libxslt libraries on your system if you wish to compile these modules.

--with-http_image_filter_module

Enables the Image Filter module that lets you apply modification to images.

Note: You will need to install the libgd library on your system if you wish to compile this module.

--with-http_geoip_module

Enables the GeoIP module for achieving geographic localization using MaxMind's GeoIP binary database.

Note: You will need to install the libgeoip library on your system if you wish to compile this module.

--with-http_sub_module

Enables the Substitution module for replacing text in web pages.

--with-http_dav_module

Enables the WebDAV module (Distributed Authoring and Versioning via Web).

--with-http_flv_module

Enables the FLV module for special handling of .flv (Flash video) files.

--with-http_mp4_module

Enables the MP4 module for special handling of .mp4 video files.

--with-http_gzip_static_module

Enables the Gzip Static module for sending pre-compressed files.

--with-http_random_index_module

Enables the Random Index module for picking a random file as the directory index.

--with-http_secure_link_module

Enables the Secure Link module to check the presence of a keyword in the URL.

--with-http_stub_status_module

Enables the Stub Status module, which generates a server statistics and information page.

--with-google_perftools_module

Enables the Google Performance Tools module.

--with-http_degradation_module

Enables the Degradation module that controls the behavior of your server depending on current resource usage.

--with-http_perl_module

Enables the Perl module allowing you to insert Perl code directly into your Nginx configuration files, and to make Perl calls from SSI.

Miscellaneous options

Other options are available in the configuration script, for example, regarding the mail server proxy feature or event management.

Mail server proxy options

--with-mail

Enables mail server proxy module. Supports POP3, IMAP4, SMTP. It is disabled by default.

--with-mail_ssl_module

Enables SSL support for the mail server proxy. It is disabled by default.

--without-mail_pop3_module

Disables the POP3 module for the mail server proxy. It is enabled by default when the mail server proxy module is enabled.

--without-mail_imap_module

Disables the IMAP4 module for the mail server proxy. It is enabled by default when the mail server proxy module is enabled.

--without-mail_smtp_module

Disables the SMTP module for the mail server proxy. It is enabled by default when the mail server proxy module is enabled.

Event management:

Allows you to select the event notification system for the Nginx sequencer. For advanced users only.

--with-rtsig_module

Enables the rtsig module to use rtsig as event notification mechanism.

--with-select_module

Enables the select module to use select as event notification mechanism. By default, this module is enabled unless a better method is found on the system—kqueue, epoll, rtsig, or poll.

--without-select_module

Disables the select module.

--with-poll_module

Enables the poll module to use poll as event notification mechanism. By default, this module is enabled if available, unless a better method is found on the system—kqueue, epoll, or rtsig.

--without-poll_module

Disables the poll module.

User and group options

--user=…

Default user account for starting the Nginx worker processes. This setting is used only if you omit to specify the user directive in the configuration file.

--group=…

Default user group for starting the Nginx worker processes. This setting is used only if you omit to specify the group directive in the configuration file.

Other options

--with-ipv6

Enables IPv6 support.

--without-http

Disables the HTTP server.

--without-http-cache

Disables HTTP caching features.

--add-module=PATH

Adds a third-party module to the compile process by specifying its path. This switch can be repeated indefinitely if you wish to compile multiple modules.

--with-debug

Enables additional debugging information to be logged.

--with-file-aio

Enables support for Asynchronous IO disk operations.

Configuration examples

Here are a few examples of configuration commands that may be used for various cases. In these examples, the path switches were omitted as they are specific to each system and leaving the default values may simply function correctly.

Note

Be aware that these configurations do not include additional third-party modules. Please refer to Chapter 5, PHP and Python with Nginx, for more information about installing add-ons.

About the prefix switch

During the configuration, you should take particular care over the --prefix switch. Many of the future configuration directives (that we will approach in further chapters) will be based on the path you select at this point. While it is not a definitive problem since absolute paths can still be employed, you should know that the prefix cannot be changed once the binaries have been compiled.

There is also another issue that you may run into if you plan to keep up with the times and update Nginx as new versions are released. The default prefix (if you do not override the setting by using the --prefix switch) is /usr/local/nginx. This is a path that does not include the version number. Consequently, when you upgrade Nginx, if you do not specify a different prefix, the new install files will override the previous ones, which among other problems, could potentially erase your currently running binaries.

It is thus recommended to use a different prefix for each version you will be using:

./configure --prefix=/usr/local/nginx-1.2.9

Additionally, to make future changes simpler, you may create a symbolic link /usr/local/nginx pointing to /usr/local/nginx-1.2.9. Once you upgrade, you can update the link to make it point to /usr/local/nginx-newer.version. This will allow the init script to always make use of the latest installed version of Nginx.

Regular HTTP and HTTPS servers

The first example describes a situation where the most important features and modules for serving HTTP and HTTPS content are enabled, and the mail-related options are disabled:

./configure --user=www-data --group=www-data --with-http_ssl_module --with-http_realip_module

As you can see, the command is rather simple and most switches were left out. The reason being is that the default configuration is rather efficient and most of the important modules are enabled. You will only need to include the http_ssl module for serving HTTPS content, and optionally, the "real IP" module for retrieving your visitors' IP addresses in case you are running Nginx as backend server.

All modules enabled

The next situation: the entire package. All modules are enabled and it is up to you whether you want to use them or not at runtime:

./configure --user=www-data --group=www-data --with-http_ssl_module --with-http_realip_module --with-http_addition_module --with-http_xslt_module --with-http_image_filter_module --with-http_geoip_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gzip_static_module --with-http_random_index_module --with-http_secure_link_module --with-http_stub_status_module --with-http_perl_module --with-http_degradation_module

This configuration opens up a wide range of possible configuration options. Chapters 3, HTTP Configuration, to Chapter 6, Apache and Nginx Together, provide more detailed information on module configuration.

With this setup, all optional modules are enabled, thus requiring additional libraries to be installed—libgeoip for the Geo IP module, libgd for the Image Filter module, libxml2, and libxslt for the XSLT module. You may install those prerequisites using your system package manager such as running yum install libxml2 or apt-get install libxml2.

Mail server proxy

This last build configuration is somewhat special as it is dedicated to enabling mail server proxy features—a darker and less documented side of Nginx. The related features and modules are all enabled:

./configure --user=www-data --group=www-data --with-mail --with-mail_ssl_module 

If you wish to completely disable the HTTP serving features and only dedicate Nginx to mail proxying, you may add the --without-http switch.

Note

Note that in the commands listed above, the user and group used for running the Nginx worker processes will be www-data, which implies that this user and group must exist on your system.

Build configuration issues

In some cases, the configure command may fail—after a long list of checks, you may receive a few error messages on your terminal. In most (if not all) cases, these errors are related to missing prerequisites or unspecified paths.

In such cases, proceed with the following verifications carefully to make sure you have all it takes to compile the application, and optionally consult the objs/autoconf.err file for more details about the compilation problem. This file is generated during the configure process and will tell you exactly where the process failed.

Make sure you installed the prerequisites

There are basically four main prerequisites: GCC, PCRE, zlib, and OpenSSL. The last three are libraries that must be installed in two packages: the library itself and its development sources. Make sure you have installed both for each of them. Please refer to the prerequisites section at the beginning of this chapter. Note that other prerequisites, such as LibXML2 or LibXSLT, might be required for enabling extra modules (for example, in the case of the HTTP XSLT module).

If you are positive that all of the prerequisites were installed correctly, perhaps the issue comes from the fact that the configure script is unable to locate the prerequisite files. In that case, make sure that you include the switches related to file paths, as described earlier.

For example, the following switch allows you to specify the location of the OpenSSL library files:

./configure [...] --with-openssl=/usr/lib64

The OpenSSL library file will be looked for in the specified folder.

Directories exist and are writable

Always remember to check the obvious; everyone makes even the simplest of mistakes sooner or later. Make sure the directory you placed the Nginx files in has read and write permissions for the user running the configuration and compilation scripts. Also ensure that all paths specified in the configure script switches are existing, valid paths.

Compiling and installing

The configuration process is of utmost importance—it generates a makefile for the application depending on the selected switches and performs a long list of requirement checks on your system. Once the configure script is successfully executed, you can proceed with compiling Nginx.

Compiling the project equates to executing the make command in the project source directory:

[[email protected] nginx-1.2.9]$ make

A successful build should result in a final message appearing: make[1]: leaving directory followed by the project source path.

Again, problems might occur at compile time. Most of these problems can originate in missing prerequisites or invalid paths specified. If this occurs, run the configure script again and triple-check the switches and all of the prerequisite options. It may also occur that you downloaded a too recent version of the prerequisites that might not be backwards compatible. In such cases, the best option is to visit the official website of the missing component and download an older version.

If the compilation process was successful, you are ready for the next step: installing the application. The following command must be executed with root privileges:

[[email protected] nginx-1.2.9]# make install

The make install command executes the install section of the makefile. In other words, it performs a few simple operations, such as copying binaries and configuration files to the specified install folder. It also creates directories for storing log and HTML files if these do not already exist. The make install step is not generally a source of problems, unless your system encounters some exceptional error, such as a lack of storage space or memory.

Note

You might require root privileges for installing the application in the /usr/local/ folder, depending on the folder permissions.

 

Controlling the Nginx service


At this stage, you should have successfully built and installed Nginx. The default location for the output files is /usr/local/nginx, so we will be basing future examples on this.

Daemons and services

The next step is obviously to execute Nginx. However, before doing so, it's important to understand the nature of this application. There are two types of computer applications—those that require immediate user input, thus running on the foreground, and those that do not, thus running in the background. Nginx is of the latter type, often referred to as daemon. Daemon names usually come with a trailing "d" and a couple of examples can be mentioned here—httpd the HTTP server daemon, named the name server daemon, or crond the task scheduler—although, as you will notice, it is not the case for Nginx. When started from the command line, a daemon immediately returns the prompt, and in most cases, does not even bother outputting data to the terminal.

Consequently, when starting Nginx you will not see any text appear on the screen and the prompt will return immediately. While this might seem startling, it is on the contrary a good sign. It means the daemon was started correctly and the configuration did not contain any errors.

User and group

It is of utmost importance to understand the process architecture of Nginx and particularly the user and groups its various processes run under. A very common source of troubles when setting up Nginx is invalid file access permissions—due to a user or group misconfiguration, you often end up getting 403 Forbidden HTTP errors because Nginx cannot access the requested files.

There are two levels of processes with possibly different permission sets:

  • The Nginx master process, which should be started as root. In most Unix-like systems, processes started with the root account are allowed to open TCP sockets on any port, whereas other users can only open listening sockets on a port above 1024. If you do not start Nginx as root, standard ports such as 80 or 443 will not be accessible. Additionally, the user directive that allows you to specify a different user and group for the worker processes will not be taken into consideration.

  • The Nginx worker processes, which are automatically spawned by the master process under the account you specified in the configuration file with the user directive (detailed in Chapter 2, Basic Nginx Configuration). The configuration setting takes precedence over the configure switch you may have entered at compile time. If you did not specify any of those, the worker processes will be started as user nobody, and group nobody (or nogroup depending on your OS).

Nginx command-line switches

The Nginx binary accepts command-line arguments for performing various operations, among which is controlling the background processes. To get the full list of commands, you may invoke the help screen using the following commands:

[[email protected] ~]$ cd /usr/local/nginx/sbin
[[email protected] sbin]$ ./nginx -h

The next few sections will describe the purpose of these switches. Some allow you to control the daemon, some let you perform various operations on the application configuration.

Starting and stopping the daemon

You can start Nginx by running the Nginx binary without any switches. If the daemon is already running, a message will show up indicating that a socket is already listening on the specified port:

[emerg]: bind() to 0.0.0.0:80 failed (98: Address already in use) […] [emerg]: still could not bind().

Beyond this point, you may control the daemon by stopping it, restarting it, or simply reloading its configuration. Controlling is done by sending signals to the process using the nginx -s command.

Command

Description

nginx –s stop

Stops the daemon immediately (using the TERM signal)

nginx –s qui t

Stops the daemon gracefully (using the QUIT signal)

nginx –s reopen

Reopens the log files

nginx –s reload

Reloads the configuration

Note that when starting the daemon, stopping it, or performing any of the preceding operations, the configuration file is first parsed and verified. If the configuration is invalid, whatever command you have submitted will fail, even when trying to stop the daemon. In other words, in some cases you will not be able to even stop Nginx if the configuration file is invalid.

An alternate way to terminate the process, in desperate cases only, is to use the kill or killall commands with root privileges:

[[email protected] ~]# killall nginx

Testing the configuration

As you can imagine, this tiny bit of detail might become an important issue if you constantly tweak your configuration. The slightest mistake in any of the configuration files can result in a loss of control over the service—you are then unable to stop it via regular init control commands, and obviously, it will refuse to start again.

In consequence, the following command will be useful to you in many occasions. It allows you to check the syntax, validity, and integrity of your configuration:

[[email protected] ~]$ /usr/local/nginx/sbin/nginx –t

The –t switch stands for test configuration. Nginx will parse the configuration anew and let you know whether it is valid or not. A valid configuration file does not necessarily mean Nginx will start though as there might be additional problems such as socket issues, invalid paths, or incorrect access permissions.

Obviously, manipulating your configuration files while your server is in production is a dangerous thing to do and should be avoided at all costs. The best practice, in this case, is to place your new configuration into a separate temporary file and run the test on that file. Nginx makes it possible by offering the –c switch:

[[email protected] sbin]$ ./nginx –t –c /home/alex/test.conf

This command will parse /home/alex/test.conf and make sure it is a valid Nginx configuration file. When you are done, after making sure that your new file is valid, proceed to replacing your current configuration file and reload the server configuration:

[[email protected]com sbin]$ cp -i /home/alex/test.conf /usr/local/nginx/conf/nginx.conf
cp: erase 'nginx.conf' ? yes
[[email protected] sbin]$ ./nginx –s reload

Other switches

Another switch that might come in handy in many situations is –V. Not only does it tell you the current Nginx build version, but more importantly it also reminds you about the arguments that you used during the configuration step—in other words, the command switches that you passed to the configure script before compilation.

[[email protected] sbin]$ ./nginx -V
nginx version: nginx/1.2.9
built by gcc 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC)
TLS SNI support enabled
configure arguments: --with-http_ssl_module

In this case, Nginx was configured with the --with-http_ssl_module switch only.

Why is this so important? Well, if you ever try to use a module that was not included with the configure script during the pre-compilation process, the directive enabling the module will result in a configuration error. Your first reaction will be to wonder where the syntax error comes from. Your second reaction will be to wonder if you even built the module in the first place! Running nginx –V will answer this question.

Additionally, the –g option lets you specify additional configuration directives in case they were not included in the configuration file:

[[email protected] sbin]$ ./nginx –g "timer_resolution 200ms";
 

Adding Nginx as a system service


In this section, we will create a script that will transform the Nginx daemon into an actual system service. This will result in mainly two outcomes—the daemon will be controllable using standard commands, and more importantly, it will automatically be launched on system startup and stopped on system shutdown.

System V scripts

Most Linux-based operating systems to date use a System-V style init daemon. In other words, their startup process is managed by a daemon called init, which functions in a way that is inherited from the old System V Unix-based operating system.

This daemon functions on the principle of runlevels, which represent the state of the computer. Here is a table representing the various runlevels and their signification:

Runlevel

State

0

System is halted

1

Single-user mode (rescue mode)

2

Multiuser mode, without NFS support

3

Full multiuser mode

4

Not used

5

Graphical interface mode

6

System reboot

You can manually initiate a runlevel transition: use the telinit 0 command to shut down your computer or telinit 6 to reboot it.

For each runlevel transition, a set of services are executed. This is the key concept to understand here: when your computer is stopped, its runlevel is 0. When you turn it on, there will be a transition from runlevel 0 to the default computer startup runlevel. The default startup runlevel is defined by your own system configuration (in the /etc/inittab file) and the default value depends on the distribution you are using: Debian and Ubuntu use runlevel 2, Red Hat and Fedora use runlevel 3 or 5, CentOS and Gentoo use runlevel 3, and so on, as the list is long.

So let us summarize. When you start your computer running CentOS, it operates a transition from runlevel 0 to runlevel 3. That transition consists of starting all services that are scheduled for runlevel 3. The question is—how to schedule a service to be started at a specific runlevel?

For each runlevel, there is a directory containing scripts to be executed. If you enter these directories (rc0.d, rc1.d, to rc6.d) you will not find actual files, but rather symbolic links referring to scripts located in the init.d directory. Service startup scripts will indeed be placed in init.d, and links will be created by tools placing them in the proper directories.

What is an init script?

An init script, also known as service startup script or even sysv script, is a shell script respecting a certain standard. The script will control a daemon application by responding to commands such as start, stop, and others, which are triggered at two levels. Firstly, when the computer starts, if the service is scheduled to be started for the system runlevel, the init daemon will run the script with the start argument. The other possibility for you is to manually execute the script by calling it from the shell:

[[email protected] ~]# service httpd start

Or if your system does not come with the service command:

[[email protected] ~]# /etc/init.d/httpd start

The script must accept at least the start and stop commands as they will be used by the system to respectively start up and shut down the service. However, for enlarging your field of action as a system administrator, it is often interesting to provide further options, such as a reload argument to reload the service configuration or a restart argument to stop and start the service again.

Note that since service httpd start and /etc/init.d/httpd start essentially do the same thing, with the exception that the second command will work on all operating systems, we will make no further mention of the service command and will exclusively use the /etc/init.d/ method.

Init script for Debian-based distributions

We will thus create a shell script for starting and stopping our Nginx daemon and also restarting and reloading it. The purpose here is not to discuss Linux shell script programming, so we will merely provide the source code of an existing init script, along with some comments to help you understand it.

Due to differences in the format of the init scripts from one distribution to another, we will here discover two separate scripts: this first one is meant for Debian-based distributions such as Debian, Ubuntu, Knoppix, and so forth.

First, create a file called nginx with the text editor of your choice, and save it in the /etc/init.d/ directory (on some systems, /etc/init.d/ is actually a symbolic link to /etc/rc.d/init.d/). In the file you just created, copy the following script carefully. Make sure that you change the paths to make them correspond to your actual setup.

You will need root permissions to save the script into the init.d directory.

Note

The complete init script for Debian-based distributions can be found in the code bundle.

Init script for Red Hat-based distributions

Due to the system tools, shell programming functions, and specific formatting that it requires, the script described above is only compatible with Debian-based distributions. If your server is operated by a Red Hat-based distribution such as CentOS, Fedora, and many more, you will need an entirely different script.

Note

The complete init script for Red Hat-based distributions can be found in the code bundle.

Installing the script

Placing the file in the init.d directory does not complete our work. There are additional steps that will be required for enabling the service. First of all, you need to make the script executable. So far, it is only a piece of text that the system refuses to run. Granting executable permissions on the script is done with the chmod command:

[[email protected] ~]# chmod +x /etc/init.d/nginx

Note that if you created the file as the root user, you will need to be logged in as root to change the file permissions.

At this point, you should already be able to start the service using service nginx start or /etc/init.d/nginx start, as well as stopping, restarting, or reloading the service.

The last step here will be to make it so the script is automatically started at the proper runlevels. Unfortunately, doing this entirely depends on what operating system you are using. We will cover the two most popular families—Debian, Ubuntu, or other Debian-based distributions and Red Hat/Fedora/CentOS, or other Red Hat-derived systems.

Debian-based distributions

For the former, a simple command will enable the init script for the system runlevel:

[[email protected] ~]# update-rc.d -f nginx defaults

This command will create links in the default system runlevel folders. For the reboot and shutdown runlevels, the script will be executed with the stop argument; for all other runlevels, the script will be executed with start. You can now restart your system and see your Nginx service being launched during the boot sequence.

Red Hat-based distributions

For the Red Hat-based systems family, the command differs, but you get an additional tool for managing system startup. Adding the service can be done via the following command:

[[email protected] ~]# chkconfig nginx on

Once that is done, you can then verify the runlevels for the service:

[[email protected] ~]# chkconfig --list nginx
Nginx  0:off   1:off   2:on    3:off   4:on    5:on    6:off

Another tool will be useful to you for managing system services, namely, ntsysv. It lists all services scheduled to be executed on system startup and allows you to enable or disable them at will:

Note

ntsysv requires root privileges to be executed.

Note that prior to using ntsysv, you must first run the chkconfig nginx on command, otherwise nginx will not appear in the list of services.

Note

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you

 

Summary


This chapter covered a number of critical steps. We first made sure that your system contained all required components for compiling Nginx. We then proceeded to select the proper version branch for your usage—will you be using the stable version or a more advanced yet potentially unstable one? After downloading the source and configuring the compilation process by enabling or disabling features and modules such as SSL, GeoIP, and more, we compiled the application and installed it on the system in the directory of your choice. We created an init script and modified the system boot sequence to schedule for the service to be started.

From this point on, Nginx is installed on your server and automatically starts with the system. Your web server is functional, though it does not yet answer the most basic functionality—serving a website. The first step towards hosting a website will be to establish a configuration file. The next chapter will cover the basic configuration of Nginx and will teach you how to optimize performance based on the expected audience and system resources.

About the Author

  • Clement Nedelcu

    Clement Nedelcu was born in France and studied at UK, French, and Chinese universities. After teaching computer science, programming, and systems administration at several eastern Chinese universities, he worked as a technology consultant in France, specialized in the web and .NET software development as well as Linux server administration. Since 2005, he has also been administering a major network of websites in his spare time, which allowed him to discover Nginx. Clement now works as CTO. for a Hong-Kong-based company developing management software for schools.

    Browse publications by this author

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