If the .boot directory contains only a single applicable file, it's booted immediately; otherwise, the loader pauses for 3–4 seconds for a key press. You can use the up and down arrows to move from one file to another, and pressEnter to select it. You can also press Home and End go to the extremes of the list. At most 10 files are displayed on the screen; to see more files, keep pressing the up or down arrows to make the list scroll.
If you don't press a key, then after the timeout, the loader boots the default image. This file is always displayed as the first item in the list, and is the file with the most recent modification time (using the larger inode number as a tie-breaker). In general this should be the image recently copied into the directory; you can use the touch utility to change the default. To determine the default, type:
ls -t /.boot | head -1
如上所述, 對於多個IFS啓動文件,可以用touch 命令更新啓動文件的時間, 默認的啓動文件是時間最新的那一個.
http://www.qnx.com/developers/docs/6.4.1/neutrino/user_guide/starting.html