Because "keys *" can block for several seconds (or longer) on large redis instances, this script scans through keys and dumps them safely. Suffers from the standard SCAN limitations, so it actually may never finish.

redis-dump-keys-safely.py

import redis
import sys

port = None
try:
    port = int(sys.argv[2])
except:
    pass
r = redis.Redis(sys.argv[1], port)

cursor = "0"
while True:
    cursor, keys = r.scan(cursor)
    for k in keys:
        print k
    if cursor == "0":
        break