MacOS – caffeinate under lion 10.7.4

The assertions are removed when the caffeinate process exits.

caffeinate creates assertions to alter system sleep behavior. If no assertion flags are specified, caffeinate creates an assertion to prevent idle sleep. If a utility is specified, caffeinate creates the assertions on the utility's behalf, and those assertions will persist for the duration of the utility's execution. Otherwise, caffeinate creates the assertions directly, and those assertions will persist until caffeinate exits.

caffeinate (or caffeinate -i) prevents idle sleep until the process is terminated by for example pressing control-C or closing a shell window. caffeinate open -Wa uTorrent would also remove the assertion when open exits.

You can get a list of power assertions with pmset -g assertions. caffeinate or caffeinate -i should set PreventUserIdleSystemSleep to 1.

To always prevent sleep when uTorrent is open, you could add a line like this to a crontab:

* * * * * pgrep -x uTorrent && caffeinate -t 60

(Use EDITOR=nano crontab -e if you haven't changed $EDITOR and don't know how to use vi.)

It might be that the majority of the OSes that people virtualise (or at least those doing so with Parallels) can only use 4 GB of RAM anyway because they are 32-bit OSes, so it would not be necessary to have more than that. You shouldn't need more than 4 GB of RAM in the virtual machine anyway, so you partly answered your question. The majority of laptops these days don't have a massive 16 GB of RAM like you do; Parallels is only looking at the market side of things there.

If you really need more, why don't you just Boot Camp (you can Boot Camp with Linux as well); that way, you will use all of your computer's power if you need it. With your SSD, it won't take too long to restart.