[vox-tech] Creating large ramdisks

[John Wojnaroski]

Micah J. Cowan wrote:

>On Mon, Feb 20, 2006 at 01:05:16PM -0800, Ken Herron wrote:
>  
>
>>John Wojnaroski wrote:
>>    
>>
>>>Hi,
>>>
>>>Is there a way to create large ramdisks (around 200meg) that act as a 
>>>single partition?  I seem to recall seeing something on the topic a 
>>>few weeks ago while surfing, but now can't seem to locate the site by 
>>>googling when I need it?
>>>      
>>>
>>Sure, it's a filesystem type called tmpfs. All of the memory for file 
>>storage is taken from the system's virtual memory (ie swap space). For 
>>example, I use this entry in /etc/fstab for my /tmp directory:
>>
>>    tmpfs           /tmp            tmpfs   size=512m       0       0
>>    
>>
>
>Yeah, but if it uses swap, doesn't that sorta defeat the probable
>purpose of a ramdisk partition?
>
>I'm pretty sure there's something that will do this, but I don't recall
>what it was... 
>  
>
Right, plus would not swap be mounted on a hard drive, excerpt from RH docs

> Swap space in Linux is used when the amount of physical memory (RAM) 
> is full. If the system needs more memory resources and the physical 
> memory is full, inactive pages in memory are moved to the swap space. 
> While swap space can help machines with a small amount of RAM, it 
> should not be considered a replacement for more RAM. Swap space is 
> located on hard drives, which have a slower access time than physical 
> memory.
>

What I'm hoping to achieve is a diskless workstation, something akin to 
ltsp but with everything (including all directories, apps, and data) 
running on the workstation after boot;  embedded it you will;  kind of 
an iPod on steroids ;-)

Download a small kernel with an initrd ( say 8megs) with PXE or 
etherboot to a ram partition /dev/ram0 that mounts the kernel and a 
minimal system that can create a large ramdisk, reset the initrd to a 
root directory (avoiding any need for pivot_root), then download a bunch 
of tarfiles from the server, untar the same, and launch applications.  
All based on scripts with no operator intervention other than throwing 
the power switch.  Think I have a handle on everything except how to 
create the large ram disk.

ATM the workstation downloads and boots to a shell prompt. would like to 
keep it under 8megs and it looks doable. Then load in all the X-windows 
stuff, additional shared libraries and apps, and launch
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