Create a RAM disk for using with XCode, with Umount disks method

xcode_ramdisk.sh

#!/bin/sh
# Create a RAM disk with same perms as mountpoint
# Script based on http://itux.idev.pro/2012/04/iservice-speed-up-your-xcode-%D0%BD%D0%B5%D0%BA%D0%BE%D1%82%D0%BE%D1%80%D1%8B%D0%B5-%D1%81%D0%BF%D0%BE%D1%81%D0%BE%D0%B1%D1%8B/ with some additions
# Usage: sudo ./xcode_ramdisk.sh start

USERNAME=$(logname)

TMP_DIR="/private/tmp"
RUN_DIR="/var/run"

USER_CACHES_DIR="/Users/$USERNAME/Library/Caches"
DEV_CACHES_DIR="/Users/$USERNAME/Library/Developer/Xcode/DerivedData"
DEV_IPHONE_DIR="/Users/$USERNAME/Library/Application Support/iPhone Simulator"
SYS_CACHES_DIR="/Library/Caches" # this must laster than USER_CACHES_DIR...

RAMDisk() {
	mntpt="$1"
	rdsize=$(($2*1024*1024/512))

	# Create the RAM disk.
	dev=`hdik -drivekey system-image=yes -nomount ram://$rdsize`
	# Successfull creation...
	if [ $? -eq 0 ] ; then
	# Create HFS on the RAM volume.
	newfs_hfs $dev
	# Store permissions from old mount point.
	eval `/usr/bin/stat -s "$mntpt"`
	# Mount the RAM disk to the target mount point.
	mount -t hfs -o union -o nobrowse -o nodev -o noatime $dev "$mntpt"
	# Restore permissions like they were on old volume.
	chown $st_uid:$st_gid "$mntpt"
	chmod $st_mode "$mntpt"
	
	echo "Creating RamFS for $mntpt $rdsize $dev"
	fi
}

UmountDisk() {
	mntpt="$1"
	dev=`mount | grep "$mntpt" | grep hfs | cut -f 1 -d ' '`
	umount -f "$mntpt"
	hdiutil detach "$dev"
	echo "Umount RamFS for $mntpt $dev"
	echo ""
}

# Test for arguments.
if [ -z $1 ]; then
echo "Usage: $0 [start|stop|restart] "
exit 1
fi

# Source the common setup functions for startup scripts
test -r /etc/rc.common || exit 1 
. /etc/rc.common

StartService () {
	ConsoleMessage "Starting RamFS disks..."

	RAMDisk "$TMP_DIR" 128
	RAMDisk "$RUN_DIR" 64
	RAMDisk "$SYS_CACHES_DIR" 64
	RAMDisk "$USER_CACHES_DIR" 1024
	RAMDisk "$DEV_CACHES_DIR" 1024
	RAMDisk "$DEV_IPHONE_DIR" 1024

	#RAMDisk /var/db 1024
	#mkdir -m 1777 /var/db/mds
}
StopService () {
	ConsoleMessage "Stopping RamFS disks..."
	
	UmountDisk "$TMP_DIR"
	UmountDisk "$RUN_DIR"
	UmountDisk "$SYS_CACHES_DIR"
	UmountDisk "$USER_CACHES_DIR"
	UmountDisk "$DEV_CACHES_DIR"
	UmountDisk "$DEV_IPHONE_DIR"
	
	# diskutil unmount /private/tmp /private/var/run
	# diskutil unmount /private/var/run
}

RestartService () {
	ConsoleMessage "Restarting RamFS disks..."
	StopService
	StartService
}

RunService "$1"

complete the StopService() and RestartService().

I seem to be experiencing a bit of a leak with SYS_CACHES. It creates ok, but doesn't remove, because grep returns two paths which detach reasonably claims don't exist. Restarting then causes an increasing number of volumes to be created

If the folder is not blank, it will not mount. Here I modify to persist the Ramdisk content:
https://gist.github.com/aazwar/7baeb7e0ca4ca259e416a735c87eb918