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# nginx

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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.

## Installation

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.

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.

## Running

Start/enable `nginx.service`.

The default page served at http://127.0.0.1 is `/usr/share/nginx/html/index.html`.

## Configuration

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 https://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.

Tip: A Nginx configuration tool has been provided by DigitalOcean.

### Configuration example

    /etc/nginx/nginx.conf

    user http;
    worker_processes auto;
    worker_cpu_affinity auto;

    events {
        multi_accept on;
        worker_connections 1024;
    }

    http {
        charset utf-8;
        sendfile on;
        tcp_nopush on;
        tcp_nodelay on;
        server_tokens off;
        log_not_found off;
        types_hash_max_size 4096;
        client_max_body_size 16M;

        # MIME
        include mime.types;
        default_type application/octet-stream;

        # logging
        access_log /var/log/nginx/access.log;
        error_log /var/log/nginx/error.log warn;

        # load configs
        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;
    }

### 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`:

    /etc/nginx/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 HTTP Server. 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`:

    /etc/nginx/nginx.conf

    ...
    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.

Note: 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:

    /etc/nginx/sites-available/example.conf

    server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;

        ...
    }

Append `include sites-enabled/*;` to the end of the `http` block:

    /etc/nginx/nginx.conf

    http {
        ...
        include sites-enabled/*;
    }

To enable a site, simply create a symlink:

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

To disable a site, unlink the active symlink:

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

Reload/restart `nginx.service` to enable changes to the sites configuration.

#### TLS

This article or section needs language, wiki syntax or style improvements. See Help:Style for reference.

Reason: Do not duplicate OpenSSL#Certificates. (Discuss in Talk:Nginx)

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

Tip:

- You may want to read the ngx_http_ssl_module documentation 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 TLS article as well as an automated tool to help create a more secure configuration.

Warning: If you plan on implementing TLS, know that some variations and implementations are still vulnerable to attack[1]. 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 openssl(1ssl) or peruse its extensive documentation.

Basic example of `/etc/nginx/nginx.conf` using TLS:

    /etc/nginx/nginx.conf

    http {
        ...
        ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH";
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ..

        # 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.)

    /etc/nginx/nginx.conf

    ...
    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

FastCGI, also FCGI, is a protocol for interfacing interactive programs with a web server. FastCGI is a variation on the earlier Common Gateway Interface (CGI); FastCGI's main aim is to reduce the overhead associated with interfacing the web server and CGI programs, allowing servers 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 php-fpm and make sure PHP has been installed and configured correctly. The main configuration file of PHP-FPM is `/etc/php/php-fpm.conf`. For basic usage the default configuration should be sufficient.

Finally, enable and start `php-fpm.service`.

Note:

- If you run nginx under a 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

When serving a PHP web-application, a `location` for PHP-FPM should to be included in each server block [2], e.g.:

    /etc/nginx/sites-available/example.conf

    server {
        root /usr/share/nginx/html;

        location / {
            index index.html index.htm index.php;
        }

        location ~ \.php$ {
            # 404
            try_files $fastcgi_script_name =404;

            # default fastcgi_params
            include fastcgi_params;

            # fastcgi settings
            fastcgi_pass			unix:/run/php-fpm/php-fpm.sock;
            fastcgi_index			index.php;
            fastcgi_buffers			8 16k;
            fastcgi_buffer_size		32k;

            # fastcgi params
            fastcgi_param DOCUMENT_ROOT	$realpath_root;
            fastcgi_param SCRIPT_FILENAME	$realpath_root$fastcgi_script_name;
            #fastcgi_param PHP_ADMIN_VALUE	"open_basedir=$base/:/usr/lib/php/:/tmp/";
        }
    }

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 configuration 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,

    fastcgi_pass 127.0.0.1:9000;

Unix domain sockets should however be faster.
Tip: To allow multiple `server` blocks using the same PHP-FPM configuration, a `php_fastcgi.conf` configuration file may be used to ease management:

    /etc/nginx/php_fastcgi.conf

    location ~ \.php$ {
        # 404
        try_files $fastcgi_script_name =404;

        # default fastcgi_params
        include fastcgi_params;

        # fastcgi settings
        ...
    }

To enable PHP support for a particular server, simply include the `php_fastcgi.conf` configuration file:

    /etc/nginx/sites-available/example.conf

    server {
        server_name example.com;
        ...

        include /etc/nginx/php_fastcgi.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 phpinfo(); ?>

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

#### CGI implementation

This implementation is needed for CGI applications.

##### fcgiwrap

Install fcgiwrap. The configuration is done by editing `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.

Override the unit `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:

    /etc/systemd/system/fcgiwrap.service

    [Unit]
    Description=Simple CGI Server
    After=nss-user-lookup.target

    [Service]
    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
    PrivateTmp=true
    Restart=on-failure

    [Install]
    WantedBy=multi-user.target

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

In `/etc/nginx`, copy the file `fastcgi_params` to `fcgiwrap_params`. In `fcgiwrap_params`, comment or delete the lines which set `SCRIPT_NAME` and `DOCUMENT_ROOT`.

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

    location ~ \.cgi$ {
         include       fcgiwrap_params;
         fastcgi_param DOCUMENT_ROOT /srv/www/cgi-bin/;
         fastcgi_param SCRIPT_NAME   myscript.cgi;
         fastcgi_pass  unix:/run/fcgiwrap.sock;
    }

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

Using `fastcgi_param SCRIPT_FILENAME /srv/www/cgi-bin/myscript.cgi` is a shortcut alternative to setting `DOCUMENT_ROOT` and `SCRIPT_NAME`. If you use `SCRIPT_FILENAME`, you also will not need to copy `fastcgi_params` to `fcgiwrap_params` and comment out the `DOCUMENT_ROOT` and `SCRIPT_NAME` lines.

Warning: If SCRIPT_NAME and DOCUMENT_ROOT are used, fcgiwrap will discard any other fastcgi_params set in nginx. You must use SCRIPT_FILENAME in order for other params (like PATH_INFO) to be settable through the Nginx configuration. See this GitHub issue.

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`.

If you get 403 errors, make sure that the CGI executable is readable and executable by the `http` user and that every parent folder is readable by the `http` user.

## 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 nodev 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`:

    /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.

    $JAIL/etc/group

    http:x:33:
    nobody:x:99:

    $JAIL/etc/passwd

    http:x:33:33:http:/:/bin/false
    nobody:x:99:99:nobody:/:/bin/false

    $JAIL/etc/shadow

    http:x:14871::::::
    nobody:x:14871::::::

    $JAIL/etc/gshadow

    http:::
    nobody:::

    # 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

Override the unit `nginx.service`. Upgrading nginx will not modify your custom .service file.

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.

    /etc/systemd/system/nginx.service

    [Unit]
    Description=A high performance web server and a reverse proxy server
    After=syslog.target network.target

    [Service]
    Type=forking
    PIDFile=/srv/http/run/nginx.pid
    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

    [Install]
    WantedBy=multi-user.target

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

Use a drop-in unit file for `nginx.service` and set the `User` and optionally `Group` options under `[Service]`:

    /etc/systemd/system/nginx.service.d/user.conf

    [Service]
    User=user
    Group=group

We can harden the service against ever elevating privileges:

    /etc/systemd/system/nginx.service.d/user.conf

    [Service]
    ...
    NoNewPrivileges=yes

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

Then we need to ensure that `user` has access to everything it needs. Follow the subsections below and then start nginx.

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

#### Port

Linux does not permit non-`root` processes to bind to ports below 1024 by default. A port above 1024 can be used:

    /etc/nginx/nginx.conf

    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:

    /etc/systemd/system/nginx.service.d/user.conf

    [Service]
    ...
    CapabilityBoundingSet=
    CapabilityBoundingSet=CAP_NET_BIND_SERVICE
    AmbientCapabilities=
    AmbientCapabilities=CAP_NET_BIND_SERVICE

Alternatively, you can use systemd socket activation. In this case, systemd will listen on the ports and, when a connection is made, spawn nginx passing the socket as a file descriptor. This means nginx requires no special capabilities as the socket already exists when it is started. This relies on an internal environment variable that nginx uses for passing sockets [3] and is therefore not officially supported. Instead of setting `CapabilityBoundingSet` and `AmbientCapabilities`, edit the service override to set the `NGINX` environment variable to tell nginx which file descriptors the sockets will be passed as:

    /etc/systemd/system/nginx.service.d/user.conf

    [Service]
    ...
    Environment=NGINX=3:4;

There will be one socket per listening port starting at file descriptor 3, so in this example we are telling nginx to expect two sockets. Now create a `nginx.socket` unit specifying what ports to listen on:

    /etc/systemd/system/nginx.socket

    [Socket]
    ListenStream=0.0.0.0:80
    ListenStream=0.0.0.0:443
    After=network.target
    Requires=network.target

    [Install]
    WantedBy=sockets.target

The sockets will be passed in the order defined in this unit, so port 80 will be file descriptor 3 and port 443 will be file descriptor 4. If you previously enabled or started the service, you should now stop it, and enable `nginx.socket` instead. When your system starts, nginx will not be running, but will be started when you access the website in a browser. With this you can harden the service further; for example, in many cases you can now set `PrivateNetwork=True` in the service file, blocking nginx from the external network, since the socket created by systemd is sufficient to serve the website over. Note that this will print a warning in the logs of the nginx service: `2020/08/29 19:33:20 [notice] 254#254: using inherited sockets from "3:4;"`

#### 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:

    /etc/tmpfiles.d/nginx.conf

    d /run/nginx 0775 root group - -

Run the configuration:

    # systemd-tmpfiles --create

Edit the PID values based on the original `nginx.service`:

    /etc/systemd/system/nginx.service.d/user.conf

    [Service]
    ...
    PIDFile=/run/nginx/nginx.pid
    ExecStart=
    ExecStart=/usr/bin/nginx -g 'pid /run/nginx/nginx.pid; error_log stderr;'
    ExecReload=
    ExecReload=/usr/bin/nginx -s reload -g 'pid /run/nginx/nginx.pid;'

#### /var/lib/nginx/*

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 are good to go.

#### Log file and 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.

### Alternative script for systemd

On pure systemd you can get advantages of chroot + systemd. [4] Based on set user group and pid with:

    /etc/nginx/nginx.conf

    user http;
    pid /run/nginx.pid;

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

    /etc/systemd/system/nginx.service

    [Unit]
    Description=nginx (Chroot)
    After=syslog.target network.target

    [Service]
    Type=forking
    PIDFile=/srv/http/run/nginx.pid
    RootDirectory=/srv/http
    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

    [Install]
    WantedBy=multi-user.target

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

Alternatively you can run only `ExecStart` as chroot with parameter `RootDirectoryStartOnly` set as `yes` (see systemd.service(5)) or start it before mount point as effective or a systemd path (see systemd.path(5)) is available.

    /etc/systemd/system/nginx.path

    [Unit]
    Description=nginx (Chroot) path
    [Path]
    PathExists=/srv/http/site/Public_html
    [Install]
    WantedBy=default.target

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.

### Better headers management

Nginx has a rather unintuitive header management system where headers can only be defined in one context, any other headers are ignored. To remedy this we can install the headers-more-nginx module.

Install the package nginx-mod-headers-more package. This will install the module to `/usr/lib/nginx/modules` directory.

To load the module add the following to the top of your main nginx configuration file.

    /etc/nginx/nginx.conf

    load_module "/usr/lib/nginx/modules/ngx_http_headers_more_filter_module.so";
    ...

## Troubleshooting

### 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 configuration.

### 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 Arch Linux, 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 127.0.0.1 -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 127.0.0.1 -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, increase the values for these keys inside the `http` block [5] [6]:

    /etc/nginx/nginx.conf

    http {
        types_hash_max_size 4096;
        server_names_hash_bucket_size 128;
        ...
    }

### Cannot assign requested address

The full error from `nginx.service` unit status is

    [emerg] 460#460: bind() to A.B.C.D:443 failed (99: Cannot assign requested address)

Even, if your nginx unit-file is configured to run after `network.target` with systemd, nginx may attempt to listen at an address that is configured but not added to any interface yet. Verify that this the case by manually running start for nginx (thereby showing the IP address is configured properly). Configuring nginx to listen to any address will resolve this issue. Now if your use case requires listening to a specific address, one possible solution is to reconfigure systemd.

To start nginx after all configured network devices are up and assigned an IP address, append `network-online.target` to `After=` within `nginx.service` and start/enable `systemd-networkd-wait-online.service`.

## See also

- WebDAV with nginx
- nginx configuration pitfalls
- Very good in-depth 2014 look at nginx security and Reverse Proxying
- Installing LEMP (nginx, PHP, MySQL with MariaDB engine and PhpMyAdmin) in Arch Linux
- Using SSL certificates generated with Let's Encrypt

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- Web server

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