Questions[memcached](ubuntu)

I have installed memached on Ubuntu 16.04 and configured in /lib/systemd/system/memcached.service system service to use a custom config /etc/memcached_server1.conf file

$ cat /lib/systemd/system/memcached.service
[Unit]
Description=memcached daemon
After=network.target

[Service]
ExecStart=/usr/share/memcached/scripts/systemd-memcached-wrapper  /etc/memcached_server1.conf

[Install]
WantedBy=multi-user.target

As you can see I'm using custom /etc/memcached_server1.conf file in the ExecStart section

After a while or because of some unknown action, /lib/systemd/system/memcached.service file resets to default /etc/memcached.conf config file ...

$ cat /lib/systemd/system/memcached.service
[Unit]
Description=memcached daemon
After=network.target

[Service]
ExecStart=/usr/share/memcached/scripts/systemd-memcached-wrapper  /etc/memcached.conf

[Install]
WantedBy=multi-user.target

To reproduce replacement I tried server reboot, systemctl restart memcached, systemctl daemon-reload but they are all useless. Nothing changes config to default one.

Question: What can cause replacement of /lib/systemd/system/memcached.service to default (after installation) one?

I am trying to use php memcache extension on Ubuntu 18.04 (nginx + PHP 7.2). Memcached is installed and working but I could not get the php-memcache extension working.

I can install libmemcached11 without any problems:

$ sudo apt-get install libmemcached11

libmemcached11 is already the newest version (1.0.18-5+deb.sury.org~xenial+2).

When I run:

$ sudo apt install libmemcached-dev

The following packages have unmet dependencies:
 libmemcached-dev : Depends: libmemcached11 (= 1.0.18-4.2ubuntu0.18.04.1) but 1.0.18-5+deb.sury.org~xenial+2 is to be installed

How can I resolve this?

Now i need install package memcached for PHP 7.3 on Ubuntu 18.4 I have server nginx, Yii2 framework and server block, but it is not work.
How can i do this ?

server {
    listen 80;
    server_name dev.advanced.ru;
    set $base_root /www/dev.advanced.ru;
    root $base_root;

    error_log /var/log/nginx/advanced.local.error.log warn;
    access_log /var/log/nginx/advanced.local.access.log main;
    charset UTF-8;
    index index.php index.html;

   location / {
    root $base_root/frontend/web;

    set $memcached_key "$uri?$args";
    memcached_pass 127.0.0.1:11211;
    error_page     404 502 504 = @fallback;

    try_files $uri $uri/ /frontend/web/index.php$is_args$args;

     location ~ ^/assets/.+\.php(/|$) {
        deny all;
        }
   }
   location /admin {
      alias $base_root/backend/web/;

   location = /admin {
      try_files $uri /backend/web/index.php$is_args$args;
     }
     try_files $uri $uri/ /backend/web/index.php$is_args$args;

     location ~ ^/admin/assets/.+\.php(/|$) {
        deny all;
     }
   }


  location ~ ^/.+\.php(/|$) {
  rewrite (?!^/((frontend|backend)/web|admin))^ /frontend/web$uri break;
  rewrite (?!^/backend/web)^/admin(/.+)$ /backend/web$1 break;

  fastcgi_pass 127.0.0.1:9000; # proxy requests to a TCP socket
  #fastcgi_pass unix:/var/run/php-fpm.sock; 
  fastcgi_split_path_info ^(.+\.php)(.*)$;
  include /etc/nginx/fastcgi_params;
  fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        try_files $fastcgi_script_name =404;
    }

    location ~ /\. {
        deny all;
    }

  location @fallback {
      proxy_pass     http://admin;
  }
}

We are seeing plenty of news coverage about these huge DDOS attacks originating from memcached servers that are exposed to the open Internet.

memcached is sometimes used to speed up performance for MySQL servers, reducing the need to go to disk for repetitive data lookups.

So the question is: How to safely run memcached in Ubuntu?