
Introducing fourmeg.zip:

fourmeg.zip is an add-on for ZipSlack which creates an 8 megabyte swap file
in your \LINUX directory.  This allows ZipSlack to boot on a machine that only
has 4 megabytes of RAM.  (at least it might...)  Even if you have more
RAM in your machine, you might still want to add this package.  For example,
you might need swap space if you add the X Window System to ZipSlack (see the
FAQ.TXT for more information on this), and adding fourmeg.zip provides a nice
example of how to make a Linux swap file.

Note that the 2.4.18 kernel is quite a bit larger than previous kernels in
ZipSlack, so you may also need to replace the default kernel with one from the
kernels/bare.i/ or kernels/lowmem.i/ (although lowmem.i is severely limited)
directories.  See the FAQ.TXT for more information on selecting a different
kernel (the Q/A about "What if the machine halts at boot").

Installing fourmeg.zip:

To install fourmeg.zip, simply unzip the file in DOS/Windows on the same 
partition where you unzipped ZipSlack.  (Be sure to unzip zipslack.zip FIRST!)
It will overwrite a few files in \LINUX such as \linux\etc\fstab, and will 
add an 8 megabyte swap file.  If you've only got 4 megabytes of RAM, you may
also wish to disable any shadow RAM in your machine's BIOS settings to make 
the maximum amount of RAM available to Linux.

How it works (for the technically curious):

fourmeg.zip does the trick by adding this file to your Linux system:

-rw-r--r--   1 root     root      8388608  Jun 12 19:43 swapfile

This file is used for swap space.  If you've got an 8 megabyte swap file
and 4 megabytes of real RAM, then you'll have 12 megabytes of virtual 
memory available for Linux.  This line in /etc/fstab tells the kernel to
activate the swap space at boot time:

/root/swapfile        swap     swap        defaults   0   0

As shipped, the file is mostly filled with zeroes, and this is why the
fourmeg.zip file can be compressed so efficiently. :^)  In fact, the
file is generated from the /dev/zero device (a never-ending supply of
zeros) using the 'dd' utility.  It is then formatted using the 'mkswap'
program.  Here's how to make a swap file manually:

dd if=/dev/zero of=swapfile bs=1k count=8192
mkswap swapfile
sync

If you need a larger swapfile, simply increase the value of 'count'.

To activate a swapfile manually, you can use 'swapon':

swapon /root/swapfile

Or, to have it made active with every boot, make sure there's a line for
it in your /etc/fstab like this one:

/root/swapfile        swap     swap        defaults   0   0

Have fun!

---
Patrick Volkerding
volkerdi@slackware.com
