Script to create and remove a RAM disk on macOS

.readme.md

How to Create a RAM Disk on macOS

This script creates a RAM disk either in a ./data subdirectory off the root of the current Git repo, or a ./data subdirectory of the current directory if not in a Git repo.

To Attach a RAM Disk

./ramdisk-macos.sh 

To Detatch the RAM disk

./ramdisk-macos.sh -d

ramdisk-macos.sh

#!/usr/bin/env bash

set -eo pipefail

# Expect "-d" for delete or "" to create
DETACH_DISK="$1"

# Number of 512 byte blocks
BLOCKS=1048576

# Mount point for ramdisk
DISK_PATH="data"

function attach_ramdisk() {
  hdiutil attach -nomount "ram://${blocks}" 2>&1 | awk '{print $1}'
}

function has_ramdisk() {
  local disk_path="$1"
  local result

  result="$(ramdisk_device "${disk_path}")"
  test "${result}" != ""
}

function ramdisk_device() {
  local disk_path="$1"

  hdiutil info | grep "${disk_path}" | awk '{print $1}'
}

function root_dir() {
  local dir
  dir="$(git rev-parse --show-toplevel 2>/dev/null||true)"
  if [ "" != "${dir}" ]; then
    echo "${dir}"
    return
  fi
  pwd
}

function main() {
  local device
  local blocks="$1"
  local disk_path="$2"
  local detach="$3"


  disk_path="$(root_dir)/${disk_path}"

  if [ "${detach}" == "-d" ] ; then
    device="$(ramdisk_device "${disk_path}")"
    echo "Detaching ramdisk at ${device} from path ${disk_path}"
    hdiutil detach "${device}"
    exit $?
  fi

  if has_ramdisk "${disk_path}"; then
    echo "Ramdisk path already exists: ${disk_path}"
    exit 1
  fi

  mkdir -p "${disk_path}"

  device="$(attach_ramdisk "${blocks}")"
  # shellcheck disable=SC2181
  if [ $? -ne 0 ] ; then
    echo "ERROR: ${device}"
    exit 1
  fi

  echo "Ramdisk attached as ${device}"

  newfs_hfs -v data "${device}"
  mount -t hfs "${device}" "${disk_path}"

  test_file="${disk_path}/.ramdisk"
  touch "${test_file}"

  echo "Ramdisk created at ${disk_path}"
}
main $BLOCKS "${DISK_PATH}" "${DETACH_DISK}"

Where can i find the /data subdirectory ?

@Darsh0307 — How did you find this?!? You commented literally 4 minutes after I posted it and before I showed it to anyone.

Anyway, the directory was intended to be <git root>/data, not /data; IOW, a subdirectory of whatever Git directory you happen to be in. If you are not in a git repo it seems it would try to create in the root, which I will update to fix.

Regarding for first one , I dont know how i came acroos it , but i found a nice way since the Title was Eye catching.

Secondly , I thought this will increase the performance of the laptop overall , But anyways really thanks for this help.

@Darsh0307 — Well, thank you for helping me recognize a bug that I have since fixed.

Now it creates it either in a subdirectory of the current directory, or a subdirectory of the root of the Git repo, whichever is the case for the current directory.

I created it so I could run tests on a program I wrote in Go that writes to a Sqlite database as well as large logs to both improve performance but also not cause the SSD on my 2015 MacBook Pro to see premature failure.

FYI, here is another Gist on the same topic: https://gist.github.com/htr3n/344f06ba2bb20b1056d7d5570fe7f596