CentOS - Jan 2007 - Centos 4.4 in a cf card + ramdisk

I want to install centos 4.4 in a CF card and use a ram disk for
operations. It means no hard disk attached to the computer. The
machine will only run an antispam antivirus gateway.
What documents can I read to make /var and /tmp sit on a ram disk and
boot the operating system in read write and switch to read only after
booting?

thanks,


-- 
------------------------------------------------------------
Erick Perez
Panama Sistemas
Integradores de Telefonia IP y Soluciones Para Centros de Datos
Panama, Republica de Panama
Cel Panama. +(507) 6694-4780
------------------------------------------------------------

Erick Perez wrote:
> I want to install centos 4.4 in a CF card and use a ram disk for
> operations. It means no hard disk attached to the computer. The
> machine will only run an antispam antivirus gateway.
> What documents can I read to make /var and /tmp sit on a ram disk and
> boot the operating system in read write and switch to read only after
> booting?
I have heard that there are read-write limitations that apply to some CF 
and similar implementations, and that the memory can "wear out" fairly
quickly.

ipcop is designed to run from cf, I suggest you have a look at it. 
Whether you use it or not, it is likely to provide you with the 
education you need.

booting from a network can be a satisfactory alternative. You might need 
a boot floppy (or CD) to get enough intelligence to mount your root 
filesystem via NFS.

You could also contemplate booting & running from CD. Is there a 
CentOS-Live? If not, there is Fedora-Live, and you could also base from 
Knoppix (first, remove almost everything) or Damn Small Linux (Knoppix 
with almost everything removed, but some additions).

fwiw I recently installed Kubuntu 6.10 on a test system. It was fairly 
easy to create a separate root filesystem, and using PXE I can boot that 
on various systems and use it for emergency/repair/recovery/inspections 
in much the same way one would use Knoppix. Except I don't have to find 
the CD.



-- 

Cheers
John

-- spambait
1aaaaaaa at coco.merseine.nu  Z1aaaaaaa at coco.merseine.nu

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On Tue, 23 Jan 2007 11:48:42 -0500
"Erick Perez" <eaperezh at gmail.com>
wrote:
> What documents can I read to make /var and /tmp sit on a ram disk and
> boot the operating system in read write and switch to read only after
> booting?
One approach that you could take is mounting the filesystem read-only,
and mounting a tmpfs filesystem as a writable overlay using unionfs.
The following paper describes various approaches how you could do this:

http://www.am-utils.org/docs/sipek-ols2006/index.html

The CentOS live CD also uses unionfs (and squashfs), so it could be
useful to look at that as a sample implementation.

-- Daniel

PS. unionfs is an additional kernel patch, and adding that to the
CentOS kernel makes it an unsupported kernel. Though, precompiled
kernels with unionfs are available through the Live CD build
infrastructure on CentOS mirrors (/centos/4.4/build/livecd).