1. Setup the device for swap usage:\\

  mkswap /dev/loop0

1. Mount the swap partition on the local loop device:
   \\

• reboot

Getting the loopback module in OpenDebianSlug is a challenge (finding the equivalent of ipkg install kernel-loop-module). There may be easier ways, but one option is to do the following (different package for versions other than 2.7beta). Ideally you would do this in the initial install.

• wget http://ipkg.nslu2-linux.org/feeds/openslug/cross/2.7-beta/kernel-module-loop_2.6.12.2-r17.1_nslu2.ipk
ipkg install kernel-module-loop_2.6.12.2-r17.1_nslu2.ipk
rm install kernel-module-loop_2.6.12.2-r17.1_nslu2.ipk

• cd /mnt
cp -Ra /lib/modules/* lib/modules
rm /mnt/.recovery

(see below for OpenDebianSlug notes)

OpenDebianSlug Notes

Getting the loopback module in OpenDebianSlug (ipkg install kernel-loop-module) is a problem. There may be easier ways, but one option is to do the following (different package for versions other than 2.7beta). Ideally you would do this in the initial install.

• reboot to flash (touch /.recovery and reboot)
• wget http://ipkg.nslu2-linux.org/feeds/openslug/cross/2.7-beta/kernel-module-loop_2.6.12.2-r17.1_nslu2.ipk
• ipkg install kernel-module-loop_2.6.12.2-r17.1_nslu2.ipk
• mount your nfs filesystem on /mnt (mount host:/dir /mnt)
• cd /mnt
• cp -Ra /lib/modules/* lib/modules
• rm /mnt/.recovery
• reboot

        losetup -d /dev/loop0\\

chmod +x /etc/init.d/swap

update-rc.d swap defaults

^D (that is pressing Ctrl+D)@@

@@cat > /etc/init.d/swap\\

^D (thay is pressing Ctrl+D)@@

Making it permanent

This is all good, but it can get a bit annoying doing that on every boot.

First, create the file /etc/init.d/swap (you may have to modify this a bit):

cat > /etc/init.d/swap
#!/bin/sh

set -e

case "$1" in
start)
echo -n "Starting swap: "
modprobe loop
losetup /dev/loop0 /swapfile
swapon /dev/loop0
echo "done"
;;
stop)
echo -n "Stopping swap: "
swapoff /dev/loop0
echo "done"
;;
restart)
swapoff /dev/loop0
swapon /dev/loop0
;;
*)
echo "Usage: swap { start | stop | restart }" >&2
exit 1
;;
esac

exit 0
^D (thay is pressing Ctrl+D)

Then make it executable:

chmod +x /etc/init.d/swap

Then make it start:

update-rc.d swap defaults

Done. On the next reboot it should mount everything.

  ipkg install kernel-module-loop\\

  modprobe loop

  losetup /dev/loop0 /mnt/swap/swapfile

N.B. Thanks to hanjo for noting the parameters on losetup we backwards.

First off, here's a shout-out to my friends (dyoung and robbat2) helping me out late at night (my timezone) and getting this job done. robbat2 is from the gentoo-embedded crew and explained this recipe to me. So no more delay... Here's the secret sauce.

I haven't run this on Unslung. It works on OpenSlug (I'll be testing some more on today's build 05/06/2005). While the slug is a great little workhorse, it's short on memory. Sometimes having a swap device comes in handy -- often while natively compiling. Sometimes one doesn't have a harddisk attached or any device attached, but a little extra memory would be great for performance or just to allow stuff to work.

1. Export a directory you want to have the swapfile in from the NFS server.
2. Change directory on the NFS server to that directory and create a swapfile. The following command creates a zeroed 128MB file called swapfile. As always be careful when using dd, and *double* check the command before you hit enter
   
   dd if=/dev/zero of=swapfile bs=1M count=128
3. Start the NFS server and portmap on the server machine if it's not already started.
4. On the TARGET (slug) NFS mount the partition. In my case it looked something like the following (192.168.1.5 is the NFS server IP address):
   
   mkdir /mnt/swap
mount -t nfs 192.168.1.5:/exported_NFS_directory /mnt/swap
5. On the TARGET, initialize the swapfile partition. N.B. I spent about 1 hour chasing down the fact that my Host and Target systems are opposite endian. So the Host created swapfile had a tiny little error when mounting the swap device. This is avoided by initializing the swapfile partition from the TARGET. The command to do this is
   
   mkswap /mnt/swap/swapfile
6. scp the loopback kernel module to the slug if you don't already have it. I'll be adding this as a default module pretty soon, but in the meantime you can just (from you build box find the loop.ko kernel module in build/tmp) and
   
   scp loop.ko root@192.168.1.5:/home/root
   \\

1. From the slug target install the kernel module if one needs to:
   
   insmod loop.ko
2. loopmount the swap file as a loop device:
   
   losetup /mnt/swap/swapfile /dev/loop0
3. Mount the swap partition on the local loop device:
   
   swapon /dev/loop0
4. Enjoy!
5. cat /proc/meminfo to see the swap space is avialable to the system
   
   cat /proc/meminfo

How To Create a NFS Swap partition (OpenSlug version)

First off, here's a shout-out to my friends (dyoung and robbat2)helping me out late at night (my timezone) and getting this job done. robbat2 is from the gentoo-embedded crew and explained this recipie to me. So no more delay... Here's the secret sause.

Why do you want an NFS swap partition

I haven't run this on Unslung. It works on OpenSlug (I'll be testing somemore on today's build 05/06/2005). While the slug is a great little workhorse, it's short on memory. Sometimes having a swap device comes in handy -- often while natively compiling. Sometimes one doesn't have a harddisk attached or any device attached, but a little extra memory would be great for performance or just to allow stuff to work.

How To do it

I'm assuming you are a little familiar with NFS and have an NFS server running.

• Export a directory you want to have the swapfile in from the NFS server.
• Change directory on the NFS server to that directory and create a swapfile. The following command creates a zeroed 128MB file called swapfile. As always be careful when using dd, and *double* check the command before you hit enter
  1. dd if=/dev/zero of=swapfile bs=1M count=128
• Start the NFS server and portmap on the server machine if it's not already started.
• On the TARGET (slug) NFS mount the partition. In my case it looked something like the following(192.168.1.5 is the NFS server IP address):
  1. mkdir /mnt/swap
  2. mount -t nfs 192.168.1.5:/exported_NFS_directory /mnt/swap
• On the TARGET, initialize the swapfile partition. N.B. I spent about 1 hour chasing down the fact that my Host and Target systems are opposite endian. So the Host created swapfile had a tiny little error when mounting the swap device. This is avoided by initializing the swapfile partition from the TARGET. The command to do this is
  1. mkswap /mnt/swap/swapfile
• scp the loopback kernel module to the slug if you don't already have it. I'll be adding this as a default module pretty soon, but in the meantime you can just (from you build box find the loop.ko kernel module in build/tmp) and
  1. scp loop.ko root@192.168.1.5:/home/root

Note: My build machine and my NFS server are the same device. Yours may be different.

• from the slug target install the kernel module if one needs to.
  1. insmod loop.ko
• loopmount the swap file as a loop device
  1. losetup /mnt/swap/swapfile /dev/loop0
• Mount the swap partition on the local loop device
  1. swapon /dev/loop0
• Enjoy!
• cat /proc/meminfo to see the swap space is avialable to the system
  1. cat /proc/meminfo