How to create a single 4GB large ramdisk?

Chris Adams linux at cmadams.net
Wed Jun 18 04:00:28 UTC 2014


> On 06/18/2014 06:52 AM, Clemens Eisserer wrote:
> >I need a single ramdisk which is a real block device (unlike tmpfs),
> >so I found the ramdisk_size kernel boot parameter.
> >However, after invoking "MAKEDEV ram" I get hundreds of 16mb large
> >ramdisks, instead of a single 4GB large:

Following up to a reply (sorry, missed original message), but I'm not
sure that's possible.  IIRC the original ramdisk block device was kind
of screwy, and I don't think it'll support that much space.

One hack I could think of to get a 4G, in-memory, block device (untested
but should work I believe):

- mount a tmpfs a little larger (don't know how much overhead there is
  so 4100m is a guess):
  mkdir /srv/foo
  mount -t tmpfs -o size=4100m tmpfs /srv/foo
- create a 4G backing file:
  dd if=/dev/zero bs=1M count=4K of=/srv/foo/backing.img
- attach it to a loopback device:
  losetup -f --show /srv/foo/backing.img

-- 
Chris Adams <linux at cmadams.net>


More information about the users mailing list