[Rule-list] Re: Swap Brainstorm

[Devon]

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On Friday 22 February 2002 11:53 am, Scott Hallock wrote:

> > Yes, once we can get swap turned on, things go pretty well.
>
> I've been pondering the problem of having to do so much initial work
> without swap for, well, a few years now.  It seems like we would
> have much better luck installing in extremely low memory situations
> if we could find and activate some swap very early in the boot
> process.

Yes, turning on some form of swap earlier in the install process would 
help greatly, no doubt about it. 

I'll spend some time looking at ways we might accomplish this. By all 
means, please feel free to try things on your own and let me know.

For example, I have just tested the worlds smallest, slowest swap device 
while trying to do an install in 10M of RAM.....

I managed to give the installer 1432k of swap as soon as the anaconda 
updates were read in, without changing any code.

I put a floppy in another machine, ran fdisk and created a partition, set 
it as swap, and ran mkswap /dev/fd0. Then, I put the disk in the floppy 
drive of the test machine as soon as it was done reading the anaconda 
updates. Switched to VT2 and entered 'swapon /dev/fd0'
While I was at it, I removed the reiserfs and the raid modules as well.

I didn't really expect it to work. I just thought it might be something 
to try.

You haven't heard a disk thrash until you try to use a floppy device as 
swap. The installer immediately began swapping, and instantly used all 
1432k. It's a good thing floppy drives are inexpensive these days, as I 
expect I'll need to replace this one soon. :)

I've added a second drive (set up as swap in advance on another machine) 
to the test machine. I just need to find a way to access it before the 
installer gets to the disk partitioning. Doing the same on a single disk 
would be good too, but probably more complicated. It'll be a good project 
for tomorrow if I get time.

Doing the install in 10M of memory with 'floppy swap', the 'free' output
looked like:
        total   used    free    shared  buffers
Mem:    7960    7324    636     0       2572    
Swap:   1432    1432    0
Total:  9392    8756    636

I used a kickstart file, and booted with:
linux ks=floppy updates mem=10M

I automated everything in the ks.cfg except turning on swap. That dialog 
had to be manually negotiated. Progress was painfully slow until 'real' 
swap could be enabled, at which point I ran 'swapoff /dev/fd0' From 
there, the install continued without difficulty.

It's not ready for prime time, nor is it for the faint of heart, but 
there you have it:
Red Hat Linux 7.2 installed in 10M of RAM. :)

- -D

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