Like tmpfs in Mac OSX

mount-ram.sh

#!/bin/sh

# This program has two feature.
#
# 1. Create a disk image on RAM.
# 2. Mount that disk image.
#
# Usage:
#   $0 <dir> <size>
#
#   size:
#     The `size' is a size of disk image (MB).
#
#   dir:
#     The `dir' is a directory, the dir is used to mount the disk image.
#
# See also:
#   - hdid(8)
#

mount_point=${1}
size=${2:-64}

mkdir -p $mount_point
if [ $? -ne 0 ]; then
    echo "The mount point didn't available." >&2
    exit $?
fi

sector=$(expr $size \* 1024 \* 1024 / 512)
device_name=$(hdid -nomount "ram://${sector}" | awk '{print $1}')
if [ $? -ne 0 ]; then
    echo "Could not create disk image." >&2
    exit $?
fi

newfs_hfs $device_name > /dev/null
if [ $? -ne 0 ]; then
    echo "Could not format disk image." >&2
    exit $?
fi

mount -t hfs $device_name $mount_point
if [ $? -ne 0 ]; then
    echo "Could not mount disk image." >&2
    exit $?
fi

umount-ram.sh

#!/bin/sh

# This program has two features.
#
# 1. Unmount a disk image.
# 2. Detach the disk image from RAM.
#
# Usage:
#   $0 <dir>
#
#   dir:
#     The `dir' is a directory, the dir is mounting a disk image.
#
# See also:
#   - hdid(8)
#

mount_point=$1
if [ ! -d "${mount_point}" ]; then
    echo "The mount point didn't available." >&2
    exit 1
fi
mount_point=$(cd $mount_point && pwd)

device_name=$(df "${mount_point}" 2>/dev/null | tail -1 | grep "${mount_point}" | cut -d' ' -f1)
if [ -z "${device_name}" ]; then
    echo "The mount point didn't mount disk image." >&2
    exit 1
fi

umount "${mount_point}"
if [ $? -ne 0 ]; then
    echo "Could not unmount." >&2
    exit $?
fi

hdiutil detach -quiet $device_name

It's cool,I used a app name iramdisk for this.

nice work!

tmpfs is not ramdisk.

Here's my take using hdiutil instead of hdid (deprecated) with mount, umount and orphan commands (and the device won't show up in Finder 😉): https://gist.github.com/Roman2K/3238fb441e298369198e