Difference between revisions of "Nginx"

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(Step 1: PHP configuration)
(Step 1: PHP configuration)
(4 intermediate revisions by 2 users not shown)
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  open_basedir = /usr/share/webapps/:/srv/http/:/home/:/tmp/:/usr/share/pear/
 
  open_basedir = /usr/share/webapps/:/srv/http/:/home/:/tmp/:/usr/share/pear/
  
If you run nginx in chrooted environment (chroot is /srv/nginx-jail, web pages are served at /srv/nginx-jail/www), the open_basedir refers to the chroot (i.e. open_basedir = /www:...) only.
+
After that let's configure modules you need. For example to use sqlite3 you should install {{ic|php-sqlite}}. Then enable it in {{ic|/etc/php/php.ini}} by uncommenting following line:
 +
extension=sqlite3.so
 +
 
 +
If you run nginx in chrooted environment (chroot is {{ic|/srv/nginx-jail}}, web pages are served at {{ic|/srv/nginx-jail/www}}), the directive refers to the chroot only (i.e. {{ic|1=open_basedir = /www}}) only.
  
 
===== Step 2: php-fpm =====
 
===== Step 2: php-fpm =====
Line 245: Line 248:
 
The configuration file is {{ic|/etc/php/php-fpm.conf}}.
 
The configuration file is {{ic|/etc/php/php-fpm.conf}}.
 
Enable and start the [[systemd]] ''php-fpm.service''.
 
Enable and start the [[systemd]] ''php-fpm.service''.
 +
 +
If you run nginx in chrooted environment (chroot is {{ic|/srv/nginx-jail}}, web pages are served at {{ic|/srv/nginx-jail/www}}), you must modify the file {{ic|/etc/php/php-fpm.conf}} to include the {{ic|chroot /srv/nginx-jail}} and {{ic|1=listen = /srv/nginx-jail/run/php-fpm/php-fpm.sock}} directives within the pool name section (a default one is {{ic|[www]}}). (Create the directory for the socket file, if missing.)
  
 
===== Step 3: Nginx configuration =====
 
===== Step 3: Nginx configuration =====
Line 411: Line 416:
 
=== Error: No input file specified ===
 
=== Error: No input file specified ===
  
Most Likely you do not have the SCRIPT_FILENAME containing the full path to your scripts.
+
1. Most Likely 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
 
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
 
  # spawn-fcgi -a 127.0.0.1 -p 9000 -f /usr/bin/php-cgi
Line 421: Line 426:
 
  # spawn-fcgi -a 127.0.0.1 -p 9000 -u www -g www -f /usr/bin/php-cgi
 
  # spawn-fcgi -a 127.0.0.1 -p 9000 -u www -g www -f /usr/bin/php-cgi
  
Another occasion is that, wrong "root" argument in the "location ~ \.php$" section in {{ic|nginx.conf}}, make sure the "root" points to the same directory as it in "location /" in the same server. Or you may just set root as global, do not define it in any location section.
+
2. Another occasion is that, wrong "root" argument in the "location ~ \.php$" section in {{ic|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.
  
Also keep in mind that your php script path was defined as {{ic|/srv/http}} by default using the variable "open_basedir" in {{ic|/etc/php/php.ini}}; you can change them if you need.
+
3. Verify that variable "open_basedir" in {{ic|/etc/php/php.ini}} also contains path you specified in "root" argument in {{ic|nginx.conf}}
  
Also notice that not only php script should have read permission, but also the entire directory structure should have execute permission so that PHP user can traverse the path.
+
4. Also notice that not only php script should have read permission, but also the entire directory structure should have execute permission so that PHP user can traverse the path.
  
 
=== Error: "File not found" in browser or "Primary script unknown" in log file ===
 
=== Error: "File not found" in browser or "Primary script unknown" in log file ===

Revision as of 09:55, 7 November 2013

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. According to Netcraft's June 2013 Web Server Survey, Nginx now hosts 14.56% of all domains worldwide, while Apache hosts about 53.34%. Nginx is now well known for its stability, rich feature set, simple configuration, and low resource consumption.

Installation

Install package nginx in the official repositories.

For a Ruby on Rails oriented installation, see The Perfect Rails Setup.

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 we create the /dev/ folder and add the devices with mknod. We 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: See man mknod and ls -l /dev/{null,random,urandom} to better understand the argument to mknod.
# 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 Folders

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 
Note: If using a 64 bit kernel you will need to create symbolic links lib64 and usr/lib64 to usr/lib: cd $JAIL; ln -s usr/lib lib64 ; ln -s usr/lib usr/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)
# cp /lib64/ld-linux-x86-64.so.2 $JAIL/lib

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
Note: Do not try to copy linux-vdso.so – it is not a real library and does not exist in /usr/lib. Also ld-linux-x86-64.so will likely be listed in /lib64 for a 64 bit system.

Copy over some misc. 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 port 0-1024), 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.
/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

Starting Service

To enable the Nginx service by default at start-up, run:

# systemctl enable nginx

To start the Nginx service, run:

# systemctl start nginx

The default served page at http://127.0.0.1 is:

/usr/share/nginx/html/index.html

Configuring

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 can be found here: Nginx Configuration Examples.

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 a server to handle more web page requests at once.

FastCGI technology is introduced into Nginx to work with many external tools, i.e.: Perl, PHP and Python. So, you cannot use these unless a FastCGI server has been started.

PHP implementation

There are different ways to run a FastCGI server for PHP. We cover php-fpm, a recommended solution.

Step 1: PHP configuration

The open_basedir in /etc/php/php.ini has to list base directories which contain PHP files, like /srv/http/ and /usr/share/webapps/:

open_basedir = /usr/share/webapps/:/srv/http/:/home/:/tmp/:/usr/share/pear/

After that let's configure modules you need. For example to use sqlite3 you should install php-sqlite. Then enable it in /etc/php/php.ini by uncommenting following line:

extension=sqlite3.so

If you run nginx in chrooted environment (chroot is /srv/nginx-jail, web pages are served at /srv/nginx-jail/www), the directive refers to the chroot only (i.e. open_basedir = /www) only.

Step 2: php-fpm

Install php-fpm. The configuration file is /etc/php/php-fpm.conf. Enable and start the systemd php-fpm.service.

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 name section (a default one is [www]). (Create the directory for the socket file, if missing.)

Step 3: Nginx configuration

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

 location ~ \.php$ {
      try_files      $uri = 404; 
      fastcgi_pass   unix:/run/php-fpm/php-fpm.sock;
      fastcgi_index  index.php;
      include        fastcgi.conf;
 }

If the root path in specified only inside a location (as it is in the default config), then either add

 root /srv/http

to the location ~ \.php$, or move it directly somewhere under server.

You could create /etc/nginx/php.conf and save this configuration there, then when needed just include this file into the server block.

 server = {
     ...
     include  php.conf;
     ...
 }

If you are going to process .html and .htm files with PHP, you should have something like this:

 location ~ \.(php|html|htm)$ {
      fastcgi_pass   unix:/var/run/php-fpm/php-fpm.sock;
      fastcgi_index  index.php;
      include        fastcgi.conf;
 }

Non .php files processing in php-fpm should be explicitly enabled in /etc/php/php-fpm.conf:

 security.limit_extensions = .php .html .htm

You need to restart the php-fpm daemon if you changed the configuration.

# systemctl restart php-fpm

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,

fastcgi_pass 127.0.0.1:9000;

Unix domain sockets are however faster.

fastcgi.conf or fastcgi_params are usually included because they hold FastCGI settings for Nginx; the use of the latter is deprecated, though. They come within the Nginx installation.

Finally, if Nginx has been working, run:

# systemctl restart nginx

If you would like to test the FastCGI implementation, create /usr/share/nginx/html/index.php with content

<?php
  phpinfo();
?> 

and visit the URL http://127.0.0.1/index.php with your browser after checking that /usr/share/nginx/html is included in open_basedir.

CGI implementation

This implementation is needed for CGI applications.

Step 1: fcgiwrap

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

The systemd unit file is currently being discussed on this ArchLinux task page. You may want to examine the unit file yourself to ensure it will work the way you want.

Multiple worker threads

If you want to spawn multiple worker threads, it's 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:

/etc/systemd/system/fcgiwrap.service
[Unit]
Description=Simple CGI Server
After=nss-user-lookup.target

[Service]
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?
Step 2: Nginx configuration

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

 location ~ \.cgi$ {
      fastcgi_pass   unix:/run/fcgiwrap.sock;
      include        fastcgi.conf;
 }

The default (Unix) socket for fcgiwrap is /run/fcgiwrap.sock.

Troubleshooting

Accessing local IP redirects to localhost

Solution from the Arch Linux forum.

Edit /etc/nginx/nginx.conf and locate the "server_name localhost" line without a # infront 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: 403 (Permission error)

This is most likely a permission error. Are you sure whatever user configured in the Nginx configuration is able to read the correct files?

If the files are located within a home directory, (e.g. /home/arch/public/webapp) and you are sure the user running Nginx has the right permissions (you can temporarily chmod all the files to 777 in order to determine this), /home/arch might be chmod 750, simply chmod it to 751, and it should work.

If you have changed your document root

If you are sure that permissions are as they should be, make sure that your document root directory is not empty. Try creating index.html in there.

Error: 404 (Pathinfo error)

In some framework (like thinkphp, cakephp) or CMS, they need the pathinfo function.

1. Edit the file /etc/php/php.ini, make sure

cgi.fix_pathinfo=1

2. Edit /etc/nginx/conf/nginx.conf, comment

location ~ \.php$ {
...
}

to

#location ~ \.php$ {
#...
#}

Then add the follows,

location ~ ^(.+\.php)(.*)$ {
  root   /srv/http/nginx;
  fastcgi_pass   unix:/var/run/php-fpm/php-fpm.sock; 	
  #fastcgi_pass   127.0.0.1:9000; #Un-comment this and comment "fastcgi_pass   unix:/var/run/php-fpm/php-fpm.sock;" if you are not using php-fpm.
  fastcgi_index  index.php;
  set $document_root2 $document_root;
  if ($document_root2 ~ "^(.*\\\\).*?[\\\\|\/]\.\.\/(.*)$") { set $document_root2 $1$2; }
  if ($document_root2 ~ "^(.*\\\\).*?[\\\\|\/]\.\.\/(.*)$") {	set $document_root2 $1$2; }
  if ($document_root2 ~ "^(.*\\\\).*?[\\\\|\/]\.\.\/(.*)$") {	set $document_root2 $1$2; }
  if ($document_root2 ~ "^(.*\\\\).*?[\\\\|\/]\.\.\/(.*)$") {	set $document_root2 $1$2; }
  if ($document_root2 ~ "^(.*\\\\).*?[\\\\|\/]\.\.\/(.*)$") {	set $document_root2 $1$2; }
  fastcgi_split_path_info ^(.+\.php)(.*)$;
  fastcgi_param	SCRIPT_FILENAME	$document_root2$fastcgi_script_name;
  fastcgi_param	PATH_INFO	$fastcgi_path_info;
  fastcgi_param	PATH_TRANSLATED	$document_root2$fastcgi_path_info;
  include	fastcgi_params;
  fastcgi_param  DOCUMENT_ROOT      $document_root2;
}

Error: The page you are looking for is temporarily unavailable. Please try again later.

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

Error: No input file specified

1. Most Likely 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. For example:

# 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

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. Verify that variable "open_basedir" in /etc/php/php.ini also contains path you specified in "root" argument in nginx.conf

4. Also notice that not only php script should have read permission, but also the entire directory structure should have execute permission so that PHP user can traverse the path.

Error: "File not found" in browser or "Primary script unknown" in log file

Ensure you've specified a root and index in your server or location directive:

 location ~ \.php$ {
      root           /srv/http/root_dir;
      index          index.php;
      fastcgi_pass   unix:/run/php-fpm/php-fpm.sock;
      include        fastcgi.conf;
 }

Error: chroot: '/usr/sbin/nginx' No such file or directory

If you encounter this error when running the daemon of nginx using chroot, this is likely due to missing 64 bit libraries in the jailed environment.

If you are running chroot in /srv/http you need to add the required 64 bit libraries.

First, set up the directories (these commands will need to be run as root)

# mkdir /srv/http/usr/lib64 
# cd /srv/http; ln -s usr/lib64 lib64

Then copy the required 64 bit libraries found using ldd /usr/sbin/nginx to /srv/http/usr/lib64

if run as root, permissions for the libraries should be read and executable for all users, so no modification is required.

Alternative Script for Systemd

On pure Systemd you can get advantages of chroot + Systemd -> Systemd for Administrators, Part VI Based on set user group an pid on:

/etc/nginx/nginx.conf
user http;
pid /run/nginx.pid;

the absolute path of 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

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

Alternatively can run only ExecStart as chroot whit parameter RootDirectoryStartOnly set as yes [man systemd service] or start it before mount point as efective or a systemd path is available.

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

to activate it systemctl enable nginx.path and change on /etc/systemd/system/nginx.service WantedBy=default.target to WantedBy=nginx.path Practicality may be that the mount point delay unless the folder to be accessible, each time the point is accessible, systemd start the server. In my case, I prefer to mount, and before Bind to existing Dir.

The PIDFile on .service file allows Systemd to monitor process(absolute Path), If not the desired behavior, you can change to default one-shoot Type, and delete the reference on .service file.


See Also