Tuesday, August 14, 2012

Playing with swap

after creating a swap partion by by Gparted tool you need to turn swapping on that partition,

swapon /dev/sdb1

swapon -s will reveal all the swap partitions

instead of free -m you need to use the free command to see the total swap and it's usage

swapon -a enables swap from /etc/fstab

we need to update the /etc/fstab to make the newly created swap partition available after reboot

in nano ctrl+k for cut and ctrl+u for uncut and by this way you can copy the existing lvm based swap line and just replace the directory,ehich in my case is /dev/sdb1

swapoff /dev/sdb1 will release the swap on the device(device and file)

swapon -a will read the /etc/fstab again and the released swap will be activated again

to create a swap from shell

fdisk /dev/sdb 

N for creating disk

T for making it swap

W for writing the partitioning table

swapon /dev/sdb1

if not succesful then try using mkswap /dev/sdb1

allocation of swap from a file

dd if=/dev/zero of=/root/swapfile bs 1024 count=524288

mkswap /root/swapfile

swapon /root/swapfile

swapon -s will show the swap

to make this parmanent modify the /etc/fstab file

it will be like

/dev/mapper/debian5-swap_1  none swap sw 0   0
/dev/sdb1                   none swap sw 0   0
/root/swapfile              swap swap defaults 0   0

swapon -a will read the /etc/fstab and show the 3 swap

swapoff -a will disable every swap in /etc/fstab

swapon -a will enable the swap in/etc/fstab

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