I would have thought it was /dev/shm, because my /etc/fstab has this line
tmpfs /dev/shm tmpfs defaults 0 0
However, when this part runs in a startup script to automatically encrypt my /tmp directory, I get an error about not being able to mount the block device:
echo -n "Mounting encrypted $TMPDEV on /tmp"
$cryptsetup -c aes-cbc-essiv:sha256 -d /dev/urandom create $CRYPTONAME $TMPDEV && \
$mke2fs -q -m 0 /dev/mapper/$CRYPTONAME >& /dev/null && \
mount /dev/mapper/$CRYPTONAME /tmp && \
chmod 1777 /tmp && daemon /bin/true || daemon /bin/false
where I've set $TMPDEV to /dev/shm.
In the old days, my /tmp directory would be something like /dev/hda10, I've been reading up on the LVM stuff but I've not been able to figure out what I need to do differently.