Fix "Failed to start php5-fpm.service: Unit php5-fpm.service is masked."

Problem:

Encounter this error message :

Failed to start php5-fpm.service: Unit php5-fpm.service is masked.

after upgrading Ubuntu with do-release-upgrade command. The problem was caused by php5 being upgraded to php7.

NOTE: Putting this down as a note for myself for future reference. You might need to change the solution given below to suit your own server's environment.

!! Always backup first before upgrade and write down the steps/commands taken !!

Solution:

1) Execute

sudo apt-get install php-fpm

2) Execute

sudo service php7.0-fpm restart

3) From /var/log/nginx :

2016/04/26 18:15:47 [crit] 1526#0: *10 connect() to unix:/var/run/php5-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 121.122.88.176, server: example.com, request: "GET /admin HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "example.com"

4) Did a ps -ef | grep fpm and the grab the configuration file used by the fpm master process

and found out that it has include=/etc/php/7.0/fpm/pool.d/*

5) Go to /etc/php/7.0/fpm/pool.d/www.conf

and found

listen = /run/php/php7.0-fpm.sock

6) Go to /etc/nginx/ and change nginx.conf

change this line:

fastcgi_pass unix:/var/run/php5-fpm.sock;

to

fastcgi_pass unix:/run/php/php7.0-fpm.sock;

7) Restart nginx

8) New problem

2016/04/26 18:27:58 [crit] 3403#0: *1 connect() to unix:/run/php/php7.0-fpm.sock failed (13: Permission denied) while connecting to upstream, client: 121.122.88.176, server: example.com, request: "GET /admin HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.0-fpm.sock:", host: "example.com"

9) Edit /etc/php/7.0/fpm/pool.d/www.conf ( please change according to your own configuration )

change

user = www-data

group = www-data

to

user = nginx

group = nginx

and

listen.owner = www-data

listen.group = www-data

to

listen.owner = nginx

listen.group = nginx