Difference between revisions of "Nginx"

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m (Test configuration: phpinfo should not be exposed to the public.)
(Adding to main configuration: Mitigate https://httpoxy.org/ vulnerabilities - See https://www.nginx.com/resources/wiki/start/topics/examples/phpfcgi/)
Line 275: Line 275:
  location ~ \.php$ {
  location ~ \.php$ {
       try_files $uri $document_root$fastcgi_script_name =404;
       try_files $uri $document_root$fastcgi_script_name =404;
      fastcgi_param HTTP_PROXY "";
       fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
       fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
       fastcgi_index index.php;
       fastcgi_index index.php;

Revision as of 02:00, 23 January 2018

nginx (pronounced "engine X"), is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server, written by Igor Sysoev in 2005. nginx is well known for its stability, rich feature set, simple configuration, and low resource consumption.

This article describes how to set up nginx and how to optionally integrate it with PHP via #FastCGI.


Install the package nginx-mainline (mainline branch: new features, updates, bugfixes) or nginx (stable branch: major bugfixes only).

Using the mainline branch is recommended. The main reason to use the stable branch is that you are concerned about possible impacts of new features, such as incompatibility with third-party modules or the inadvertent introduction of bugs in new features [1].

Note: All nginx modules available in the official repositories require the nginx package (as opposed to nginx-mainline) as a dependency. It may be wise to review the list of modules for any you might need/want before making the nginx vs nginx-mainline decision. Modules for nginx-mainline can be found in the Arch User Repository.

For a chroot-based installation for additional security, see #Installation in a chroot.


Start/enable nginx.service.

The default page served at is /usr/share/nginx/html/index.html.


First steps with nginx are described in the Beginner’s Guide. You can modify the configuration by editing the files in /etc/nginx/ The main configuration file is located at /etc/nginx/nginx.conf.

More details and examples can be found in http://wiki.nginx.org/Configuration and the official documentation.

The examples below cover the most common use cases. It is assumed that you use the default location for documents (/usr/share/nginx/html). If that is not the case, substitute your path instead.

Configuration example

user http;
worker_processes auto;
worker_cpu_affinity auto;
pcre_jit on;

events {
    worker_connections 2048;

http {
    include mime.types;
    default_type application/octet-stream;
    sendfile on;
    tcp_nopush on;
    aio threads;
    server_tokens off; # Security: Disables nginx version in error messages and in the “Server” response header field.
    charset utf-8; # Force usage of UTF-8
    index index.php index.html index.htm;
    # include sites-enabled/*; # See Server blocks

General configuration

Processes and connections

You should choose a fitting value for worker_processes. This setting ultimately defines how many connections nginx will accept and how many processors it will be able to make use of. Generally, making it the number of hardware threads in your system is a good start. Alternatively, worker_processes accepts the auto value since versions 1.3.8 and 1.2.5, which will try to autodetect the optimal value (source).

The maximum connections nginx will accept is given by max_clients = worker_processes * worker_connections.

Running under different user

By default, nginx runs the master process as root and worker processes as user http. To run worker processes as another user, change the user directive in nginx.conf:

user user [group];

If the group is omitted, a group whose name equals that of user is used.

Tip: It is also possible to run nginx without anything running as root using systemd. See #Running unprivileged using systemd.

Server blocks

It is possible to serve multiple domains using server blocks. These are comparable to "VirtualHosts" in Apache. Also see the upstream examples.

In the example below the server listens for incoming connections on IPv4 and IPv6 ports 80 for two domains, domainname1.dom and domainname2.dom:

server {
        listen 80;
        listen [::]:80;
        server_name domainname1.dom;
        root /usr/share/nginx/domainname1.dom/html;
        location / {
           index index.php index.html index.htm;

server {
        listen 80;
        listen [::]:80;
        server_name domainname2.dom;
        root /usr/share/nginx/domainname2.dom/html;

Restart nginx.service to apply any changes.

Make sure the hostnames are resolvable by setting up a DNS-server like BIND or dnsmasq, or have a look at Network configuration#Local network hostname resolution.

Managing server entries

It is possible to put different server blocks in different files. This allows you to easily enable or disable certain sites.

Create the following directories:

# mkdir /etc/nginx/sites-available
# mkdir /etc/nginx/sites-enabled

Create a file inside the sites-available directory that contains one or more server blocks:

server {

Append the following line at the end of the http block in /etc/nginx/nginx.conf:

include sites-enabled/*;

To enable a server, simple create a symlink:

# ln -s /etc/nginx/sites-available/example /etc/nginx/sites-enabled/example

To remove a server, delete the symlink:

# unlink /etc/nginx/sites-enabled/example

Reload or restart nginx.service to enable the new configuration.


OpenSSL provides TLS/SSL support and is installed by default on Arch installations.

  • You may want to read the ngx_http_ssl_module docs first before configuring SSL.
  • Let’s Encrypt is a free, automated, and open certificate authority. A plugin is available to request valid SSL certificates straight from the command line and automatic configuration.
  • Mozilla has a useful SSL/TLS article which includes nginx specific configuration guidelines as well as an automated tool to help create a more secure configuration.
  • Cipherli.st provides strong SSL implementation examples and tutorial for most modern webservers.
Warning: If you plan on implementing TLS, know that some variations and implementations are still vulnerable to attack[2]. For details on these current vulnerabilities within TLS and how to apply appropriate changes to nginx, visit https://weakdh.org/sysadmin.html

Create a private key and self-signed certificate. This is adequate for most installations that do not require a CSR:

# mkdir /etc/nginx/ssl
# cd /etc/nginx/ssl
# openssl req -new -x509 -nodes -newkey rsa:4096 -keyout server.key -out server.crt -days 1095
# chmod 400 server.key
# chmod 444 server.crt
Note: The -days switch is optional and RSA keysize can be as low as 2048 (default).

If you need to create a CSR, follow these instructions instead of the above:

# mkdir /etc/nginx/ssl
# cd /etc/nginx/ssl
# openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:4096 -out server.key
# chmod 400 server.key
# openssl req -new -sha256 -key server.key -out server.csr
# openssl x509 -req -days 1095 -in server.csr -signkey server.key -out server.crt
Note: For more openssl options, read its man page or peruse its extensive documentation.

Example of a nginx.conf using SSL:

http {
        ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH";
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_session_cache shared:SSL:10m;
        add_header Strict-Transport-Security "max-age=63072000; includeSubdomains; preload";
        add_header X-Frame-Options DENY;
        add_header X-Content-Type-Options nosniff;
        ssl_session_tickets off;
        ssl_stapling on;
        ssl_stapling_verify on;
        resolver valid=300s; # Google DNS Servers
        resolver_timeout 5s;

# Redirect to HTTPS
server {
        listen 80;
        server_name localhost;
        return 301 https://$host$request_uri;

server {
        #listen 80; # Uncomment to also listen for HTTP requests
        listen 443 ssl http2; # HTTP/2 is only possible when using SSL
        server_name localhost;

        ssl_certificate ssl/server.crt;
        ssl_certificate_key ssl/server.key;

        root /usr/share/nginx/html;
        location / {
            index index.html index.htm;

Restart nginx.service to apply any changes.

Per-User Directories

To replicate Apache-style ~user URLs to users' ~/public_html directories, try the following. (Note: if both rules are used, below, the more-specific PHP rule must come first.)

server {
    # PHP in user directories, e.g. http://example.com/~user/test.php
    location ~ ^/~(.+?)(/.+\.php)$ {
        alias          /home/$1/public_html$2;
        fastcgi_pass   unix:/run/php-fpm/php-fpm.sock;
        fastcgi_index  index.php;
        include        fastcgi.conf;

    # User directories, e.g. http://example.com/~user/
    location ~ ^/~(.+?)(/.*)?$ {
        alias     /home/$1/public_html$2;
        index     index.html index.htm;
        autoindex on;

See #PHP implementation for more information on PHP configuration with nginx.

Restart nginx.service to enable the new configuration.


FastCGI, also FCGI, is a protocol for interfacing interactive programs with a web server. FastCGI is a variation on the earlier CGI (Common Gateway Interface); FastCGI's main aim is to reduce the overhead associated with interfacing the web server and CGI programs, allowing a server to handle more web page requests at once.

FastCGI technology is introduced into nginx to work with many external tools, e.g. Perl, PHP and Python.

PHP implementation

PHP-FPM is the recommended solution to run as FastCGI server for PHP. Install the php and php-fpm packages and configure PHP as described on the PHP page.

The main configuration file of PHP-FPM is /etc/php/php-fpm.conf, then enable and start the systemd unit php-fpm.service.

  • If you run nginx under different user, make sure that the PHP-FPM socket file is accessible by this user, or use a TCP socket.
  • If you run nginx in chrooted environment (chroot is /srv/nginx-jail, web pages are served at /srv/nginx-jail/www), you must modify the file /etc/php/php-fpm.conf to include the chroot /srv/nginx-jail and listen = /srv/nginx-jail/run/php-fpm/php-fpm.sock directives within the pool section (a default one is [www]). Create the directory for the socket file, if missing. Moreover, for modules that are dynamically linked to dependencies, you will need to copy those dependencies to the chroot (e.g. for php-imagick, you will need to copy the ImageMagick libraries to the chroot, but not imagick.so itself).
nginx configuration
Adding to main configuration

Inside each server block serving a PHP web application should appear a location block similar to:

location ~ \.php$ {
     try_files $uri $document_root$fastcgi_script_name =404;
     fastcgi_param HTTP_PROXY "";
     fastcgi_pass unix:/run/php-fpm/php-fpm.sock;
     fastcgi_index index.php;
     fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
     include fastcgi.conf;

If it is needed to process other extensions with PHP (e.g. .html and .htm):

location ~ \.(php|html|htm)$ {

Non .php extension processing in PHP-FPM should also be explicitly added in /etc/php/php-fpm.d/www.conf:

security.limit_extensions = .php .html .htm
Note: Pay attention to the fastcgi_pass argument, as it must be the TCP or Unix socket defined by the chosen FastCGI server in its config file. The default (Unix) socket for php-fpm is:
fastcgi_pass unix:/run/php-fpm/php-fpm.sock;

You might use the common TCP socket, not default,

Unix domain sockets should however be faster.
PHP configuration file

If using multiple server blocks with enabled PHP support, it might be easier to create a PHP config file instead:

location ~ \.php$ {

To enable PHP support for a particular server, simple include php.conf:

 server {
     server_name example.com;
     include php.conf;
Test configuration

You need to restart the php-fpm.service and nginx.service units if the configuration has been changed in order to apply changes.

To test the FastCGI implementation, create a new PHP file inside the root folder containing:

<?php var_export($_SERVER)?>

Navigate this file inside a browser and you will see the informational page with the current PHP configuration.

CGI implementation

This implementation is needed for CGI applications.


Install fcgiwrap. The configuration file is /usr/lib/systemd/system/fcgiwrap.socket. Enable and start fcgiwrap.socket.

Multiple worker threads

If you want to spawn multiple worker threads, it is recommended that you use multiwatchAUR, which will take care of restarting crashed children. You will need to use spawn-fcgi to create the unix socket, as multiwatch seems unable to handle the systemd-created socket, even though fcgiwrap itself does not have any trouble if invoked directly in the unit file.

Copy the unit file from /usr/lib/systemd/system/fcgiwrap.service to /etc/systemd/system/fcgiwrap.service (and the fcgiwrap.socket unit, if present), and modify the ExecStart line to suit your needs. Here is a unit file that uses multiwatchAUR. Make sure fcgiwrap.socket is not started or enabled, because it will conflict with this unit:

Description=Simple CGI Server

ExecStartPre=/bin/rm -f /run/fcgiwrap.socket
ExecStart=/usr/bin/spawn-fcgi -u http -g http -s /run/fcgiwrap.sock -n -- /usr/bin/multiwatch -f 10 -- /usr/sbin/fcgiwrap
ExecStartPost=/usr/bin/chmod 660 /run/fcgiwrap.sock


Tweak -f 10 to change the number of children that are spawned.

Warning: The ExecStartPost line is required because of strange behaviour I'm seeing when I use the -M 660 option for spawn-fcgi. The wrong mode is set. This may be a bug?
nginx configuration

Inside each server block serving a CGI web application should appear a location block similar to:

location ~ \.cgi$ {
     root           /path/to/server/cgi-bin;
     fastcgi_pass   unix:/run/fcgiwrap.sock;
     include        fastcgi.conf;

The default socket file for fcgiwrap is /run/fcgiwrap.sock.

If you keep getting a 502 - bad Gateway error, you should check if your CGI-application first announces the mime-type of the following content. For html this needs to be Content-type: text/html.

Installation in a chroot

Installing nginx in a chroot adds an additional layer of security. For maximum security the chroot should include only the files needed to run the nginx server and all files should have the most restrictive permissions possible, e.g., as much as possible should be owned by root, directories such as /usr/bin should be unreadable and unwriteable, etc.

Arch comes with an http user and group by default which will run the server. The chroot will be in /srv/http.

A perl script to create this jail is available at jail.pl gist. You can either use that or follow the instructions in this article. It expects to be run as root. You will need to uncomment a line before it makes any changes.

Create necessary devices

nginx needs /dev/null, /dev/random, and /dev/urandom. To install these in the chroot create the /dev/ directory and add the devices with mknod. Avoid mounting all of /dev/ to ensure that, even if the chroot is compromised, an attacker must break out of the chroot to access important devices like /dev/sda1.

Tip: Be sure that /srv/http is mounted without no-dev option
Tip: See mknod(1) and ls -l /dev/{null,random,urandom} to better understand the mknod options.
# export JAIL=/srv/http
# mkdir $JAIL/dev
# mknod -m 0666 $JAIL/dev/null c 1 3
# mknod -m 0666 $JAIL/dev/random c 1 8
# mknod -m 0444 $JAIL/dev/urandom c 1 9

Create necessary directories

nginx requires a bunch of files to run properly. Before copying them over, create the folders to store them. This assumes your nginx document root will be /srv/http/www.

# mkdir -p $JAIL/etc/nginx/logs
# mkdir -p $JAIL/usr/{lib,bin}
# mkdir -p $JAIL/usr/share/nginx
# mkdir -p $JAIL/var/{log,lib}/nginx
# mkdir -p $JAIL/www/cgi-bin
# mkdir -p $JAIL/{run,tmp}
# cd $JAIL; ln -s usr/lib lib
# cd $JAIL; ln -s usr/lib lib64
# cd $JAIL/usr; ln -s lib lib64

Then mount $JAIL/tmp and $JAIL/run as tmpfs's. The size should be limited to ensure an attacker cannot eat all the RAM.

# mount -t tmpfs none $JAIL/run -o 'noexec,size=1M'
# mount -t tmpfs none $JAIL/tmp -o 'noexec,size=100M'

In order to preserve the mounts across reboots, the following entries should be added to /etc/fstab:

 tmpfs   /srv/http/run   tmpfs   rw,noexec,relatime,size=1024k   0       0
 tmpfs   /srv/http/tmp   tmpfs   rw,noexec,relatime,size=102400k 0       0

Populate the chroot

First copy over the easy files.

# cp -r /usr/share/nginx/* $JAIL/usr/share/nginx
# cp -r /usr/share/nginx/html/* $JAIL/www
# cp /usr/bin/nginx $JAIL/usr/bin/
# cp -r /var/lib/nginx $JAIL/var/lib/nginx

Now copy over required libraries. Use ldd to list them and then copy them all to the correct location. Copying is preferred over hardlinks to ensure that even if an attacker gains write access to the files they cannot destroy or alter the true system files.

$ ldd /usr/bin/nginx
linux-vdso.so.1 (0x00007fffc41fe000)
libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f57ec3e8000)
libcrypt.so.1 => /usr/lib/libcrypt.so.1 (0x00007f57ec1b1000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f57ebead000)
libm.so.6 => /usr/lib/libm.so.6 (0x00007f57ebbaf000)
libpcre.so.1 => /usr/lib/libpcre.so.1 (0x00007f57eb94c000)
libssl.so.1.0.0 => /usr/lib/libssl.so.1.0.0 (0x00007f57eb6e0000)
libcrypto.so.1.0.0 => /usr/lib/libcrypto.so.1.0.0 (0x00007f57eb2d6000)
libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f57eb0d2000)
libz.so.1 => /usr/lib/libz.so.1 (0x00007f57eaebc000)
libGeoIP.so.1 => /usr/lib/libGeoIP.so.1 (0x00007f57eac8d000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f57eaa77000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007f57ea6ca000)
/lib64/ld-linux-x86-64.so.2 (0x00007f57ec604000)

For files residing in /usr/lib you may try the following one-liner:

# cp $(ldd /usr/bin/nginx | grep /usr/lib | sed -sre 's/(.+)(\/usr\/lib\/\S+).+/\2/g') $JAIL/usr/lib

And the following for ld-linux-x86-64.so:

# cp /lib64/ld-linux-x86-64.so.2 $JAIL/lib
Note: Do not try to copy linux-vdso.so: it is not a real library and does not exist in /usr/lib.

Copy over some miscellaneous but necessary libraries and system files.

# cp /usr/lib/libnss_* $JAIL/usr/lib
# cp -rfvL /etc/{services,localtime,nsswitch.conf,nscd.conf,protocols,hosts,ld.so.cache,ld.so.conf,resolv.conf,host.conf,nginx} $JAIL/etc

Create restricted user/group files for the chroot. This way only the users needed for the chroot to function exist as far as the chroot knows, and none of the system users/groups are leaked to attackers should they gain access to the chroot.

# touch $JAIL/etc/shells
# touch $JAIL/run/nginx.pid

Finally make set very restrictive permissions. As much as possible should be owned by root and set unwritable.

# chown -R root:root $JAIL/

# chown -R http:http $JAIL/www
# chown -R http:http $JAIL/etc/nginx
# chown -R http:http $JAIL/var/{log,lib}/nginx
# chown http:http $JAIL/run/nginx.pid

# find $JAIL/ -gid 0 -uid 0 -type d -print | xargs chmod -rw
# find $JAIL/ -gid 0 -uid 0 -type d -print | xargs chmod +x
# find $JAIL/etc -gid 0 -uid 0 -type f -print | xargs chmod -x
# find $JAIL/usr/bin -type f -print | xargs chmod ug+rx
# find $JAIL/ -group http -user http -print | xargs chmod o-rwx
# chmod +rw $JAIL/tmp
# chmod +rw $JAIL/run

If your server will bind port 80 (or any other port in range [1-1023]), give the chrooted executable permission to bind these ports without root.

# setcap 'cap_net_bind_service=+ep' $JAIL/usr/bin/nginx

Modify nginx.service to start chroot

Before modifying the nginx.service unit file, it may be a good idea to copy it to /etc/systemd/system/ since the unit files there take priority over those in /usr/lib/systemd/system/. This means upgrading nginx would not modify your custom .service file.

# cp /usr/lib/systemd/system/nginx.service /etc/systemd/system/nginx.service

The systemd unit must be changed to start up nginx in the chroot, as the http user, and store the pid file in the chroot.

Note: I'm not sure if the pid file needs to be stored in the chroot jail.
 Description=A high performance web server and a reverse proxy server
 After=syslog.target network.target
 ExecStartPre=/usr/bin/chroot --userspec=http:http /srv/http /usr/bin/nginx -t -q -g 'pid /run/nginx.pid; daemon on; master_process on;'
 ExecStart=/usr/bin/chroot --userspec=http:http /srv/http /usr/bin/nginx -g 'pid /run/nginx.pid; daemon on; master_process on;'
 ExecReload=/usr/bin/chroot --userspec=http:http /srv/http /usr/bin/nginx -g 'pid /run/nginx.pid; daemon on; master_process on;' -s reload
 ExecStop=/usr/bin/chroot --userspec=http:http /srv/http /usr/bin/nginx -g 'pid /run/nginx.pid;' -s quit
Note: Upgrading nginx with pacman will not upgrade the chrooted nginx installation. You have to take care of the updates manually by repeating some of the steps above. Do not forget to also update the libraries it links against.

You can now safely get rid of the non-chrooted nginx installation.

# pacman -Rsc nginx

If you do not remove the non-chrooted nginx installation, you may want to make sure that the running nginx process is in fact the chrooted one. You can do so by checking where /proc/PID/root symmlinks to. If should link to /srv/http instead of /.

# ps -C nginx | awk '{print $1}' | sed 1d | while read -r PID; do ls -l /proc/$PID/root; done

Tips and tricks

Running unprivileged using systemd

Edit nginx.service and set the User and optionally Group options under [Service]:


We can harden the service against ever elevating privileges:

Tip: See systemd.exec(5) for more options of confinement.

Then we need to ensure that user has access to everything it needs:

Linux does not permit non-root processes to bind to ports below 1024 by default. A port above 1024 can be used:
server {
        listen 8080;
Tip: If you want nginx accessible on port 80 or 443, configure your firewall to redirect requests from 80 or 443 to the ports nginx listens to.

Or you may grant the nginx process the CAP_NET_BIND_SERVICE capability which will allow it to bind to ports below 1024:


PID file
nginx uses /run/nginx.pid by default. We can create a directory that user has write access to and place our PID file in there. An example using systemd-tmpfiles:

d /run/nginx 0775 root group - -

Run the configuration:

# systemd-tmpfiles --create

Edit nginx.service:

ExecStart=/usr/bin/nginx -g 'pid /run/nginx/nginx.pid; error_log stderr;' # copied from nginx.service
ExecReload=/usr/bin/nginx -s reload -g 'pid /run/nginx/nginx.pid;'

Some directories under /var/lib/nginx need to be bootstrapped by nginx running as root. It is not necessary to start the whole server to do that, nginx will do it on a simple configuration test. So just run one of those and you're good to go.

Log file & Directory Permissions
The step of running a configuration test will create a dangling root-owned log. Remove logs in /var/log/nginx to start fresh.
The nginx service user needs write permission to /var/log/nginx. This may require changing permission and/or ownership of this directory on your system.

Now we should be good to go. Go ahead and start nginx, and enjoy your completely rootless nginx.

Tip: The same setup may be desirable for your FastCGI server as well.

Alternative script for systemd

On pure systemd you can get advantages of chroot + systemd. [3] Based on set user group an pid on:

user http;
pid /run/nginx.pid;

the absolute path of file is /srv/http/etc/nginx/nginx.conf.

Description=nginx (Chroot)
After=syslog.target network.target

ExecStartPre=/usr/sbin/nginx -t -c /etc/nginx/nginx.conf
ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf
ExecReload=/usr/sbin/nginx -c /etc/nginx/nginx.conf -s reload
ExecStop=/usr/sbin/nginx -c /etc/nginx/nginx.conf -s stop


It is not necesary to set the default location, nginx loads at default -c /etc/nginx/nginx.conf, but it is a good idea though.

Alternatively you can run only ExecStart as chroot with parameter RootDirectoryStartOnly set as yes man systemd service or start it before mount point as effective or a systemd path is available.

Description=nginx (Chroot) path

Enable the created nginx.path and change the WantedBy=default.target to WantedBy=nginx.path in /etc/systemd/system/nginx.service.

The PIDFile in unit file allows systemd to monitor process (absolute path required). If it is undesired, you can change to default one-shot type, and delete the reference from the unit file.

Nginx Beautifier

nginxbeautifierAUR is a commandline tool used to beautify and format nginx configuration files.


Configuration validation

# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

Accessing local IP redirects to localhost

Solution from the Arch Linux forum.

In /etc/nginx/nginx.conf locate the server_name localhost line without a # in front of it, and add below:

server_name_in_redirect off;

Default behavior is that nginx redirects any requests to the value given as server_name in the config.

Error: The page you are looking for is temporarily unavailable. Please try again later. (502 Bad Gateway)

This is because the FastCGI server has not been started, or the socket used has wrong permissions.

Try out this answer to fix the 502 error.

In Archlinux, the configuration file mentioned in above link is /etc/php/php-fpm.conf.

Error: No input file specified

1. Verify that variable open_basedir in /etc/php/php.ini contains the correct path specified as root argument in nginx.conf (usually /usr/share/nginx/). When using PHP-FPM as FastCGI server for PHP, you may add fastcgi_param PHP_ADMIN_VALUE "open_basedir=$document_root/:/tmp/:/proc/"; in the location block which aims for processing php file in nginx.conf.

2. Another occasion is that, wrong root argument in the location ~ \.php$ section in nginx.conf. Make sure the root points to the same directory as it in location / in the same server. Or you may just set root as global, do not define it in any location section.

3. Check permissions: e.g. http for user/group, 755 for directories and 644 for files. Remember the entire path to the html directory should have the correct permissions. See File permissions and attributes#Bulk chmod to bulk modify a directory tree.

4. You do not have the SCRIPT_FILENAME containing the full path to your scripts. If the configuration of nginx (fastcgi_param SCRIPT_FILENAME) is correct, this kind of error means php failed to load the requested script. Usually it is simply a permissions issue, you can just run php-cgi as root:

# spawn-fcgi -a -p 9000 -f /usr/bin/php-cgi

or you should create a group and user to start the php-cgi:

# groupadd www
# useradd -g www www
# chmod +w /srv/www/nginx/html
# chown -R www:www /srv/www/nginx/html
# spawn-fcgi -a -p 9000 -u www -g www -f /usr/bin/php-cgi

5. If you are running php-fpm with chrooted nginx ensure chroot is set correctly within /etc/php-fpm/php-fpm.d/www.conf (or /etc/php-fpm/php-fpm.conf if working on older version)

Warning: Could not build optimal types_hash

When starting the nginx.service, the process might log the message:

[warn] 18872#18872: could not build optimal types_hash, you should increase either types_hash_max_size: 1024 or types_hash_bucket_size: 64; ignoring types_hash_bucket_size

To fix this warning, inside the http block include the following:

http {
    types_hash_max_size 4096;
    server_names_hash_bucket_size 128;

See also