Creating RAM disk in macOS

macos-ramdisk.md

Built-in

diskutil erasevolume HFS+ 'RAM Disk' `hdiutil attach -nobrowse -nomount ram://XXXXX`

where XXXXX is the size of the RAM disk in terms of memory blocks.

Notes:

$2048$ memory blocks correspond to 1MB. Thus, XXXXX = YYYY * 2048 where YYYY is the size in MB.

E.g.

• ram://2048 will create 1MB RAM disk
• ram://2097152 --> 1 GB
• ram://4194304 --> 2 GB
• ram://8388608 --> 4 GB

Third-party Tools

• TmpDisk:: Open Source RAM disk management app.
• Ultra RAM Disk installs as a menu bar item that allows you to create RAM disks when needed.
• RAMDisk: is an app for creating as well as backing up RAM disks, to allow you to save their contents as well as restore RAM disks when you restart your Mac.
• RAMDiskCreator

Resources

• https://bogner.sh/2012/12/os-x-create-a-ram-disk-the-easy-way/
• https://blog.macsales.com/46348-how-to-create-and-use-a-ram-disk-with-your-mac-warnings-included
• https://www.jakobstoeck.de/2017/ramdisk-for-faster-applications-under-macos/

@kvaDrug. hdiutil detach /dev/disk2 works for me

diskutil erasevolume HFS+ 'RAM Disk' disk0 `hdiutil detach /dev/disk0 -nobrowse -nomount ram://33554415`

thats true ?

use APFS instead of HFS+, you may gain a better performance(based on test with Blackmagic)

The same for xonsh shell:

diskutil erasevolume HFS+ 'myramdisk' @$(hdiutil attach -nobrowse -nomount ram://@(2097152*1))
ls /Volumes/myramdisk
hdiutil detach @($(df | grep ram1g).split(' ')[0])

Built a modern version here, supports APFS: https://github.com/johnalanwoods/RAMDisk

mount at very specific mount point.

Please tell me if you know how do the same, but with JHFS+ and without EFI partition.

Adjust commands for actual values

$ hdiutil attach  -nomount  -mountroot target  ram://8388608 
/dev/disk6
$ diskutil apfs createContainer /dev/disk6  
Creating container with disk6
Started APFS operation on disk6
Creating a new empty APFS Container
Unmounting Volumes
Switching disk6 to APFS
Creating APFS Container
Created new APFS Container disk7
Disk from APFS operation: disk7
Finished APFS operation on disk6
$ diskutil apfs addVolume disk7 apfs name -nomount  
Will export new APFS Volume "name" from APFS Container Reference disk7
Started APFS operation on disk7
Preparing to add APFS Volume to APFS Container disk7
Creating APFS Volume
Created new APFS Volume disk7s1
Disk from APFS operation: disk7s1
Finished APFS operation on disk7
$ hdiutil attach -mountpoint /your/target/path /dev/disk7s1 
/dev/disk7s1        	41504F50-0000-11AA-AA11-00306B4 /your/target/path

mount_tmpfs also works, but it require root privileges