Place pork shoulder in a large stockpot. Cover with water and beer. Add pickling spice (I usually loosely tie in cheese cloth or use a tea infuser).
Bring the pot to a boil and then immediately lower to a bare simmer. You want to cook this low and slow. You will be cooking the roast for a total time of 25-30 minutes per lb. In this case for an 8 lb. roast I will simmer it for a total of 3 hours and 30 minutes. Remember that you will be adding the vegetables near the end of the cooking time.
Now it's time for the garlic. Separate the cloves from the head and lay them on the cutting board. One at a time lay your knife on top of the clove. Make sure the edge is on the cutting board. Place the heel of your hand on the side of the and firmly press down until the clove is crushed. Dump all the garlic into the pot. I started out with six cloves, then added six more later. I would even go to a full head of garlic next time, since I used a lot of water and beer to cover the roast so that all the salt would be extracted during the long simmer.
Peel and cut rutabaga into large cubes. Cut cabbage into 8 chunks, leaving attached to the core. Do the same with onions if you are not using small onions. Leaving them attached at the core will keep them together as they cook. Chunk up carrot and other vegetables. Peel and cut potato into medium chunks.
Carefully use tongs or several slotted spoons to remove the smoked pork shoulder from the pot and place in a bowl or platter to cool.
Add all prepared vegetables and simmer for 30-45 minutes until all are fork tender. I usually add the rutabaga and carrots first as they take the longest to cook. I lay the cabbage chunks on top and let them steam. When cabbage is done, so should all the other vegetables.
Serve with butter, a good mustard, rye bread and beer.