A tradition bordering with cult. One isn't a proper host unless by New Year there's a vat of sour cabbage ready.
First of all, no vinegar in the recipe. Just salt, water and some spice - laurels, whole black pepper and sometimes a few cuts of beet.
Second, the cabbage is not shred. At least, not all of it - only as much as it takes to fill the space between the heads. Heads have only the outer leaves torn and the core cut out; they are otherwise left intact.
The recipe requires a few magic operations - like washing out at times, or warming up at others. Occasional eavesdropping to know when it started to whisper.
One important piece is the heavy object on top of the vat, so the heads don't float - the fermentation is strictly anaerobic. If exposed to air for a while, cabbage may actually rot. It was quite common for a household to have a heavy stone somewhere, which would be thoroughly scrubbed and washed come end of October, to be placed on top of the vat. At some point, no city dared do any roadwork on cobbled streets in late Fall, because if one stone was left dislodged, by morning there would be dozens of stones missing - people would just steal them to press their cabbage. Nowadays, it's usually a larger water canister - 20 liters will do, or even 10.
How much sour cabbage does a household need for a winter? It depends on the size - usually it's about five heads per head - and their menu. Sour cabbage is eaten as a salad, but there is also podvarak (pieces of meat and/or bacon with sour cabbage on a pilav plate in the oven; sour cabbage with dried & smoked ribs; and above all, sarma). Another important use is for rasol (raz-sol, salt-away), i.e. the salt water imbued with the juices of the fermented cabbage.