Create a RAM disk in Linux

Create a RAM disk in Linux

Category : How-to

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Linux penguinThere are many reasons for creating a memory based file system in Linux, not least of which is to provide a near zero latency and extremely fast area to story files. A prime use of a RAM disk is for application caching directories or work areas.

There are two main types of RAM disk which can be used in Linux and each have their own benefits and weaknesses:

  • ramfs
  • tmpfs

See my other post for the differences between ramfs and tmpfs.

Check the amount of free RAM you have left on your machine before creating a RAM disk. Use the Linux command free to see the unused RAM. The below is an example of a 31GB of ram in a production server.

free -g
       total used free shared buffers cached
Mem:   31    29   2    0      0       8
-/+ buffers/cache: 20 11
Swap:  13    6    7

The free command shows the amount of RAM availale on your system in addition to the amount of memory used, free and used for caching. SWAP space is also displayed and shows if your system is writing memory to disk.

Create a folder to use as a mount point for your RAM disk.

mkdir /mnt/ramdisk

Then use the mount command to create a RAM disk.

mount -t [TYPE] -o size=[SIZE] [FSTYPE] [MOUNTPOINT]

Substitute the following attirbutes for your own values:

  • [TYPE] is the type of RAM disk to use; either tmpfs or ramfs.
  • [SIZE] is the size to use for the file system. Remember that ramfs does not have a physical limit and is specified as a starting size.
  • [FSTYPE] is the type of RAM disk to use; either tmpfsramfsext4, etc.


mount -t tmpfs -o size=512m tmpfs /mnt/ramdisk

You can add the mount entry into /etc/fstab to make the RAM disk persist over reboots. Remember however, that the data will disappear each time the machine is restarted.

vi /etc/fstab
tmpfs       /mnt/ramdisk tmpfs   nodev,nosuid,noexec,nodiratime,size=1024M   0 0

See my other post for the differences between ramfs and tmpfs.



7-Aug-2014 at 5:54 pm

Thanks for this post and the one about rams vs tmpfs.

I’m making great use of it!

# mount | grep tmpfs | wc -l


31-Dec-2014 at 8:11 pm

Very informative!

Cy O’Hara

15-Jan-2015 at 1:58 pm

Hi, Newbie here, silly question time. Just done the free -g and the mkdir /mnt/ramdisk test, which revealed a field full of 0’s and “permission denied”, is there any advice on this?


    26-Oct-2015 at 4:59 pm

    You need to type in sudo mkidir /mnt/ramdisk
    Because this is what allows you to do that (sudo)


15-Jan-2015 at 2:47 pm

I’m not quite following what happened in your scenario but if you are getting permission denied it’s because you don’t have access to write to the /mnt/ folder. You could try running this as root.


16-May-2015 at 1:50 am

Thanks James. My two used computers are running like a rocket with Linux Mint and a Ramdisk.

    Ram Sambamurthy

    14-Feb-2017 at 1:47 am

    Can you explain how it’s running like a rocket? What did you do exactly with Linux Mint? What’s using the ramdisk?

Hardened Criminal

24-May-2015 at 3:28 am

Thank you!
You made my whole day better.


3-Jun-2015 at 10:47 am

Great article – thank you!

Darpan Agarwal .

10-Oct-2015 at 1:03 pm

mount -t -tmpfs -o size=21m tmpfs /mnt/ramdisk

showing error i.e. Unknown fs type ‘tmpfs’.


    20-Oct-2015 at 5:35 pm

    Maybe you shuould remove the “-” before “-tmpfs”:

    mount -t tmpfs …


10-Oct-2015 at 2:46 pm

What’s the difference between `[TYPE]` and `[FSTYPE]` in the command:
`mount -t [TYPE] -o size=[SIZE] [FSTYPE] [MOUNTPOINT]`? Aren’t they always the same representing the file system type?


22-Nov-2015 at 1:34 am

Thank you :)


18-Dec-2015 at 9:16 pm

Great article,but I have one question. In windows I have a program (Primo Ramdisk) that can create RAM disk dinamically, so when use some space from it it will take from sistem RAM and when I delete the information from it, it will return to the system RAM. In this situation I will have back to my System RAM all memory that its availlable if I dont have anything in DISK RAM. So my question is this function tmpfs can do that or the memory alocated to DISK RAM is lost for the System RAM even if its not used? Or if you know a similar program that exist for linux like mine used in windows that can do that?


26-Mar-2016 at 9:39 am

Thank you, this was very helpful to me.
Could some one clarify when using a ramfs ramdisk and I delete a file from it (using Gnome) is the file file still kept on the ramdisk?
Say I have a sensitive document that I decrypted to the ramdisk and then I want to delete the file without removing the ramdisk is it safe to delete it using Gnome?


    23-Feb-2021 at 2:29 pm

    I realize that this is several years late …

    Using the rm command will just remove the directory entry for the file; the actual file will not be purged from memory until that memory is required for something else or a power-off (even with a reboot, it is possible that the RAM will not be sufficiently purged.)

    Instead of using the rm command, look into using the shred command.


9-Oct-2016 at 12:13 pm

Anyone have any idea why htop didn’t print used memory by ramdisk ?


1-Dec-2016 at 6:59 pm

It was very informative. thanks


14-Mar-2017 at 7:53 pm

This article and the one on the differences between ramfs and tempfs are very helpful.

There is an obvious mistake however. It must of course be
emacs /etc/fstab

;) Thank you and best regards!


    14-Mar-2017 at 8:03 pm

    Nooo – the post is 100% correct ;)

    Otherwise I get an error.

Pravallika KG

3-Jul-2017 at 1:17 pm

Hi James,

When i am running ‘mount -t tmpfs -o size=1m tmpfs /mnt/ramdisk’, i am getting following error:
mount: mounting tmpfs on /mnt/ramdisk/ failed: Invalid argument

Do i need any special permissions like should i be root user or anything? Please help me where i am missing?

    James Larrowe

    10-Jun-2018 at 8:17 pm

    Remove the tmpfs before /mnt/ramdisk and run it as root.


23-Sep-2017 at 3:44 am

Hello James,
This isn’t a RAM disk but a RAM filesystem


23-Apr-2018 at 6:56 pm

As ZuluPro mentioned, this is not RAM disk but a RAM filesystem. Creating RAM disk would create a entry in /dev/ dir I believe.

Sean Brennan

26-May-2018 at 8:19 pm

40 minutes to mere seconds to populate a mysql database with 50 megabytes of data blobs numbering 64 thousand entries. Seriously mysql seems to be all about transactions and in-memory processing just crushed traditional disk based approaches. Thanks, man!


17-Feb-2019 at 5:29 pm

Hi, James,

Thanks for taking the trouble to teach us about Linux’s in-memory file systems. Just what I need.

Whilst your posts on this subject are clear and — I’m happy to believe till otherwised proven — error-free, I think an important piece of info is missing: How can I get rid of the file system and reclaim the RAM it uses when I’ve finished with it— apart from by rebooting of course?

Lothar Scholz

12-Jul-2019 at 11:05 pm

I can’t specify options or file system type without becoming root. Is there any way i can create the ram filesystem in my home directory and mount it from my .profile init script ?


4-Jan-2020 at 4:37 pm

The explanation above is for a tmpfs and not ramfsI believe.
In fedora /tmp is already tmpfs type!

I am wonderingif there any benefits of creating tempfs and not using the /tmp


13-Nov-2020 at 9:14 am

great article, but it’s lacking one thing to be perfect: section about unmounting:
sudo umount -f /mnt/ramdisk


2-Mar-2021 at 9:49 am

Here we are, over 7 years later, and your post is the #1 or #2 result when Googling “linux mount ramdisk”. It’s an easy read, clear, concise, and to the point — everything a good post should be. Congratulations, and thank you!


2-Mar-2022 at 1:00 pm

Great writeup.

One thing:
“Remember however, that the data will disappear each time the machine is restarted.”
This isn’t true! I’ve added an entry to fstab and the files exist after a restart.
This is on ubuntu 21.10.

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