Build. Create Ram Disk

A Ram disk is can be useful for many purposes.  

In particular when creating a root fs during the building of a boot image.

To create a 4MB Ext2 Ram disk

1. Check that /dev/ram0 exists, or create the device file using mknod

2. Zero the device with, dd if=/dev/zero of=/dev/ram0 bs=1k count=4096

3. Create the file system with, mke2fs -m 0 -N 2000 /dev/ram0

The ramdisk can now be mounted with, mount -t ext2 /dev/ram0 /mnt

4Mb may not be sufficient to build a modern Linux root fs.  The ramdisk can be resized, after dismounting.  Resizing will destroy the data on the device.

To create a 10MB Ex2 Ram disk

dd if=/dev/zero of=/dev/ram0 bs=1k count=10240

mk2fs -m 0 -N 4000 /dev/ram0

The resized ramdisk can now be mounted.

Notes: -m is the reserved space. -N 4000 specifies 4000 inodes.  An inode is roughly equivalent to a file or folder entry in a file allocation table.  A filesystem containing mainly small files, will required more inodes than a filesystem containing a few large files.