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.  (Wow!  Can you believe it? :^)  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 2.2.6 kernel is quite a bit larger than version 2.0 was, so you
may also need to replace the default kernel with one from the kernels/bare.i/
or kernels/lowmem.i/ 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.

NOTE:  Since fourmeg.zip replaces /linux/--linux-.---, if you unzip fourmeg.zip
on a ZipSlack installation that's had some use, you might lose file attributes
(like long filename information) on files you've added to the topmost Linux
directory (/, or the DOS \LINUX directory) since the installation.  In general,
this shouldn't be too big a problem -- just rename the files and reset the
permissions if need be.  You could also move them out of / from within Linux
before you unzip fourmeg.zip in DOS/Windows.

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 Jul 30 19:04 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:

/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=1024 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 /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:

/swapfile        swap     swap        defaults   0   0

Have fun!

---
Patrick Volkerding
[email protected]
[email protected]

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