NGINX: pid: Get process id of the nginx

‘pid’ directive is used to store the process ID of the main process.

Usually you can get the process id of nginx, by executing the command ‘ps -eaf | grep nginx

$ps -eaf | grep nginx
    0 64258     1   0 11:22AM ??         0:00.04 nginx: master process nginx
   -2 68050 64258   0 12:38PM ??         0:00.00 nginx: worker process
188003303 68155 26600   0 12:39PM ttys000    0:00.00 grep nginx

As you see the output, 64258 is the process id of nginx master process.

You can get the same by looking at the contents of pid file.

How to get the pid file location?

Execute the command ‘nginx -V’.    

$nginx -V
nginx version: nginx/1.17.3
built by clang 10.0.1 (clang-1001.0.46.4)
built with OpenSSL 1.1.1c  28 May 2019 (running with OpenSSL 1.1.1d  10 Sep 2019)
TLS SNI support enabled
configure arguments: --prefix=/usr/local/Cellar/nginx/1.17.3_1 --sbin-path=/usr/local/Cellar/nginx/1.17.3_1/bin/nginx --with-cc-opt='-I/usr/local/opt/pcre/include -I/usr/local/opt/openssl@1.1/include' --with-ld-opt='-L/usr/local/opt/pcre/lib -L/usr/local/opt/openssl@1.1/lib' --conf-path=/usr/local/etc/nginx/nginx.conf --pid-path=/usr/local/var/run/nginx.pid --lock-path=/usr/local/var/run/nginx.lock --http-client-body-temp-path=/usr/local/var/run/nginx/client_body_temp --http-proxy-temp-path=/usr/local/var/run/nginx/proxy_temp --http-fastcgi-temp-path=/usr/local/var/run/nginx/fastcgi_temp --http-uwsgi-temp-path=/usr/local/var/run/nginx/uwsgi_temp --http-scgi-temp-path=/usr/local/var/run/nginx/scgi_temp --http-log-path=/usr/local/var/log/nginx/access.log --error-log-path=/usr/local/var/log/nginx/error.log --with-compat --with-debug --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_degradation_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-ipv6 --with-mail --with-mail_ssl_module --with-pcre --with-pcre-jit --with-stream --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module

Search for the property ‘--pid-path’.

--pid-path=/usr/local/var/run/nginx.pid

Open the file ‘/usr/local/var/run/nginx.pid’, you can get the pid of the process.   

$cat /usr/local/var/run/nginx.pid
64258

How to change the pid file?

Using ‘pid’ directive, you can change the pid file location.

pid /nginx_conf_details/my_nginx.pid;

Step 1: Stop nginx server.

Step 2: Update nginx.conf file.

nginx.conf

pid /nginx_conf_details/my_nginx.pid;

events {
}

http {
    include mime.types;

    server {
        listen 9090;

        server_name localhost;

        location = /about{
            return 200 "Hello Welcome to NGINX";
        }

        location = /not_found{
            return 404 "File can't be found";
        }
    }
}

Step 3: Start nginx server (sudo nginx).

Step 4: Confirm the process id.

$cat /nginx_conf_details/my_nginx.pid
71481
$
$ps -eaf | grep nginx
    0 71481     1   0  1:50PM ??         0:00.00 nginx: master process nginx
   -2 71482 71481   0  1:50PM ??         0:00.00 nginx: worker process
188003303 71488 26600   0  1:50PM ttys000    0:00.00 grep nginx
$

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