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If you want to modify existing lines you (/home and /home/user/MyDocs) you should modify file /usr/lib/genfstab.awk

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I have used vi to change /usr/lib/gensftab.awk. The changes thus applied are indeed in /etc/fstab. However, as mentioned elswhere in this thread, at boot time fstab is not used. Nonetheless, a changed /etc/fstab makes manually mounting easier.

Code added at the end of /usr/lib/genfstab.awk:
END
{
print "/dev/mmcblk1p1 /media/mmc1 vfat umask=0000 0 0"
print "/dev/mapper/xx /media/tt1 ext3 defaults 0 0"
print "/dev/mmcblk1p3 /media/tt2 ext3 defaults 0 0"
}

The code reflects my sd card (16GB):
mmcblk1p1 = 2 GB vfat
mmcblk1p2 = 5 GB luks-encrypted ext3, after opening with luks-password available in /dev/mapper/xx
mmcblk1p3 = 9 GB ext3

more info on the encryption can be found in this thread:
http://talk.maemo.org/showthread.php?t=40154