To create a RAM-based block device in Ubuntu.

DONG9992026-02-04 8:24

To create a RAM-based block device in Ubuntu, use the

brd (RAM block device) kernel module to create a fast, memory-backed device (/dev/ram* ), or use tmpfs for simpler, file-based RAM storage. The brd method offers higher IOPS and mimics a real physical block device, ideal for performance testing or secure, temporary storage.

Method 1: Using brd (Kernel RAM Block Device)

This creates an actual block device in RAM, allowing for partitioning and file systems.

Load the brd module and create a 1GB RAM disk (size is in KiB):

bash
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```
sudo modprobe brd rd_nr=1 rd_size=1048576 max_part=1
```
- rd_nr=1 : Creates one device (/dev/ram0 ).
- rd_size=1048576 : Size in KiB (
  
  1024×1024=1GB1024 cross 1024 equals 1 GB
  1024×1024=1GB ).
Format the RAM disk (e.g., ext4):

bash
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```
sudo mkfs.ext4 /dev/ram0
```

Mount the device :

bash

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sudo mkdir /mnt/ramdisk
sudo mount /dev/ram0 /mnt/ramdisk

Clean up (unmount and remove module):

bash
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```
sudo umount /mnt/ramdisk
sudo rmmod brd
```

Method 2: Using tmpfs (Temporary File System)

tmpfs is generally easier, acts like a ramdisk, and can swap to disk if RAM runs out.

Create mount point :

bash
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```
sudo mkdir /mnt/ramdisk
```

Mount as tmpfs (e.g., 1GB):

bash

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sudo mount -t tmpfs -o size=1G tmpfs /mnt/ramdisk

Summary Table

Feature	`brd` (Method 1)	`tmpfs` (Method 2)
Type	Actual Block Device	Filesystem in RAM
Performance	Highest IOPS	High
Swap	No	Yes (may swap to disk)
Setup	`modprobe` + `mkfs`	`mount -t tmpfs`

Note: Any data on a RAM disk is lost upon reboot or when the module is removed.