Just use random words. Memorable passwords don’t have to be weak. Five random common english words are already very strong. Just make sure you don’t pick the words by hand.
I would be very cautious about using shuf for password generation, since it doesn't use a cryptographically-secure random number generator (I just checked the source).
Edit: I see that shuf permits the use of custom seeds, so you can do the following, and it will be secure:
Except this has stopped being strong a while ago, since it has been popularized by xkcd in 2011 cracker have incorporated this scheme in their password cracking routines.
Except Schneier is just plain wrong about this. The numbers presented in XKCD comic were already assuming that the attacker has full knowledge about how the passwords are generated, including the wordlist used. This has been discussed over and over in various places, including HN. Long story short, there is no shortcuts for attacker against true random bits of entropy.