Example:

>> Clear cache

> Flush database 2 with telnet
# telnet REDIS_IP_OR_FQDN 6379
> auth xxxxxxx_PASWORD_HERE_xxxxxxx
> select 2
> flushdb

> Completely flush ALL
telnet REDIS_IP_OR_FQDN 6379
> auth xxxxxxx_PASWORD_HERE_xxxxxxx
> flushall