I have two options to set a password for Redis.
1.using redis-cli:
root@server:~# redis-cli
redis 127.0.0.1:6379> AUTH your_redis_password
(error) ERR Client sent AUTH, but no password is set
redis 127.0.0.1:6379> CONFIG SET requirepass "mypass"
OK
redis 127.0.0.1:6379> AUTH mypass
Ok
remove password
root@server:~# redis-cli
redis 127.0.0.1:6379> CONFIG SET requirepass "mypass"
OK
redis 127.0.0.1:6379> AUTH mypass
Ok
redis 127.0.0.1:6379> CONFIG SET requirepass ""
OK
redis 127.0.0.1:6379> AUTH PASSWORD
(error) ERR Client sent AUTH, but no password is set
2.edit redis.conf file
Open redis configuration file redis.conf
sudo vi /etc/redis/redis.conf
find and uncomment line # requirepass foobared, then restart server
################################## SECURITY ###################################
# Require clients to issue AUTH <PASSWORD> before processing any other
# commands. This might be useful in environments in which you do not trust
# others with access to the host running redis-server.
#
# This should stay commented out for backward compatibility and because most
# people do not need auth (e.g. they run their own servers).
#
# Warning: since Redis is pretty fast an outside user can try up to
# 150k passwords per second against a good box. This means that you should
# use a very strong password otherwise it will be very easy to break.
#
# requirepass foobared
Uncomment following line and set strong password by removing default one.
Default Configuration
#requirepass foobaredConfiguration after Setting Password
requirepass MyStr0ngPnow you password is MyStr0ngP
redis-cli -h example.com -p 6379 -a MyStr0ngP#d
Set and Connect to Redis Database with Password
https://techmonger.github.io/70/redis-password/
How To Secure Your Redis Installation on Ubuntu
redis: set a password for redis
https://stackoverflow.com/questions/7537905/redis-set-a-password-for-redis