Wednesday, December 31, 2014

Create a SWAP partition on the Arduino Yun

This will create a 128MB (=2x RAM) swap partition on the Yun's SD card. I already have 2 partitions on the SD, this will be the 3th. First create an extra partition and format it as explained at

http://myyafa.blogspot.be/2014/05/create-and-format-partitions-on-yun-sd.html

  After another reboot (maybe using mount command this reboot isn't needed?), df displays:
Filesystem           1K-blocks      Used Available Use% Mounted on
rootfs                 4183000    410916   3562372  10% /
/dev/root                 7680      7680         0 100% /rom
tmpfs                    30560       112     30448   0% /tmp
tmpfs                      512         0       512   0% /dev
/dev/sda1              4183000    410916   3562372  10% /
/dev/sda2              3138272    112080   2868908   4% /mnt/sda2
/dev/sda3               129267      7982    114732   7% /mnt/sda3
Next do:
root@Arduino:~# umount /dev/sda3
root@Arduino:~# mkswap /dev/sda3
Setting up swapspace version 1, size = 131068 KiB
no label, UUID=54a098ed-4e70-4392-8232-bd1f394df68a
root@Arduino:~# swapon /dev/sda3
Probably if I hadn't rebooted or so, the unmounting wasnt necessary... In /etc/config/fstab add:
config swap
        option device   /dev/sda3
        option enabled  1

swapiness can be controlled via:
sysctl -w vm.swappiness=10
echo 10 > /proc/sys/vm/swappiness
This will not remember the value across booting. For that edit /etc/sysctl.conf so that it contains:
vm.swappiness = 10

The free command or 'swapon -s' command can be given to get info about your swap.

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