mjhjmtu

I'm in the process of upgrading from Ubuntu Server 16.04 to 18.04 and at the same time upgrading from PHP 5.6 to PHP 7.3.

In /etc/memcached.conf I added:

-s /tmp/memcached.sock
-a 666

When I restart the service, I see:

srw-rw-rw- 1 memcache memcache 0 Nov 13 03:44 /tmp/systemd-private-7fc3b73707084a93bcc6abd22001eb7e-memcached.service-oIF206/tmp/memcached.sock=

How can I configure PHP to know where the unix socket is?

systemd has PrivateTmp=true for memcached.service

One way would be to override PrivateTmp, specifically for the memcached.service, i.e.

mkdir -p /etc/systemd/system/memcached.service.d
echo "[Service]" > /etc/systemd/system/memcached.service.d/override.conf
echo "PrivateTmp=false" >> /etc/systemd/system/memcached.service.d/override.conf
systemctl daemon-reload
systemctl restart memcached

That would change the memcached.service back to using /tmp, rather than /tmp/systemd-private-...

Assuming you want to use memcached for session handling; Once you've verified that /tmp/memcahced.sock exists with the correct permissions, in /etc/php.ini or /etc/php/conf.d/memcached.ini change session support.

[Session]
extension=memcached.so
session.save_handler="memcached"
session.save_path="/tmp/memcached.sock"

If it exists, comment out session.save_handler=files.

FWIW, if it's on the Internet, and given it's memcached which has been exploited a lot recently, disabling UDP and binding explicitly to 127.0.0.1 would be worth additional consideration, i.e. add these to your memcached options -U 0 -l 127.0.0.1