1. cat  /proc/11233/limits

Max open files            65535                65535                files

2. cat   /usr/lib/systemd/system/openresty.service

# /usr/lib/systemd/system/openresty.service
[Unit]
Description=The OpenResty Application Platform
After=syslog.target network.target remote-fs.target nss-lookup.target

[Service]
Type=forking
PIDFile=/usr/local/openresty/nginx/logs/nginx.pid
ExecStartPre=/usr/local/openresty/nginx/sbin/nginx -t
ExecStart=/usr/local/openresty/nginx/sbin/nginx
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s QUIT $MAINPID
PrivateTmp=true
LimitNOFILE=65535
[Install]
WantedBy=multi-user.target

用一个例子来演示会更加清晰