How to use Memcached in a UNIX socket

Memcached can run in a UNIX socket, which provides better performance than a TCP connection.

Note: If Memcached fails to start, it is usually due to permission and user problems. Please use root privilege to execute the following instructions, and verify that the socket path is writable to the designated user.

Stop Memcached
```
systemctl stop memcached
```

Copy the service file

cp /usr/lib/systemd/system/memcached.service /etc/systemd/system/memcached.service

Add the following content to /etc/systemd/system/memcached.service. After [Service], please change username to the same user that runs PHP:
```
User=username
Group=username
```
The contents of the file should look like this:
Edit /etc/sysconfig/memcached, changing the path to your desired location, and the username to the same one used in Step 3:
```
OPTIONS=""
USER="memcached"
```
becomes
```
OPTIONS="-s /path/to/memcached.sock -a 0770"
USER="username"
```
Start Memcached again:
```
systemctl start memcached
```
Verify it started successfully:
```
systemctl status memcached
```
Check if everything is working well:
```
nc -U /path/to/memcached.sock
stats
```
If there is still a permission issue, please check selinux status:
```
getenforce
```
Disable selinux if status shows Enforcing:
```
setenforce 0 
```
(reboot will re-enable selinux)
To permanently disable selinux, edit /etc/selinux/config, change enforcing to permissiveordisabled and then reboot.

Stop Memcached
```
systemctl stop memcached
```
Edit /etc/sysconfig/memcached and change
```
OPTIONS=""
USER=""
```
to
```
OPTIONS="-s /path/to/memcached.sock -a 0770"
USER="username"
```
where USER is the same user that runs PHP.
Start Memcached
```
service memcached start
```
Check if everything is working well:
```
nc -U /path/to/memcached.sock
stats
```
If there is still a permission issue, please check selinux status:
```
getenforce
```
Disable selinux if status shows Enforcing:
```
setenforce 0 
```
(reboot will re-enable selinux)
To permanently disable selinux, edit /etc/selinux/config, change enforcing to permissiveordisabled and then reboot.

Stop Memcached
```
systemctl stop memcached
```
Edit /etc/memcached.conf, comment out host and port, add socket path and permission
```
-s /path/to/memcached.sock
-a 0770
```
and change -u memcache to -u username where username is the same user that runs PHP.
Start Memcached again
```
systemctl start memcached
```
Check if everything is working well:
```
nc -U /path/to/memcached.sock
stats
```

Stop Memcached
```
service memcached stop
```
Edit /etc/memcached.conf, comment out host and port, add socket path and permission
```
-s /path/to/memcached.sock
-a 0770
```
and change -u memcache to -u username where username is the same user that runs PHP.
Start Memcached again
```
service memcached start
```
Check if everything is working well:
```
nc -U /path/to/memcached.sock
stats
```

How to use Memcached in a UNIX socket

For Centos7.X

for Centos6.X

For Ubuntu 17.10, Ubuntu 16.04, Debian 8 and Debian 9

for Ubuntu 14.04 and Debian 7