For those experiencing on Debian buster:
Editing
nano /etc/systemd/system/redis.service
and adding this line below redis [Service]
ExecStartPost=/bin/sh -c "echo $MAINPID > /var/run/redis/redis.pid"
It suppose to look like this:
[Service]
Type=forking
ExecStart=/usr/bin/redis-server /etc/redis/redis.conf
ExecStop=/bin/kill -s TERM $MAINPID
ExecStartPost=/bin/sh -c "echo $MAINPID > /var/run/redis/redis.pid"
PIDFile=/run/redis/redis-server.pid
then:
sudo systemctl daemon-reload
sudo systemctl restart redis.service
Check redis.service status:
sudo systemctl status redis.service
The pid file now should appear.