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if you have no swap in your installation this is what you do??? Why???




A while ago while Thomas Schmitt was helping me with dd and xorriso in
backing up systems and partitions into usb and back the issue of not
having a swap partition in my system came up, since I chose not to
during the installation, and how to create one, lead me into a search of
doing just that.

In the page
https://askubuntu.com/questions/33697/how-do-i-add-a-swap-partition-after-system-installation
there are instructions that I believe work just as well on Debian to
either create a new partition for swap or create a swap file, which I
did not know it was an option.
I chose the second as my partitioning has become complex and most of the
drive is not available during boot-up.  So I assume it would run to an
error if I did this on a partition that is not available during boot.

Below you will find the exact instructions I used and worked fine for me
on Stretch (I believe to be true for all Debian).

But here come some questions:
1	What is the difference functionally of having a swap partition from
having a swap file?  Is it that you can use a separate physical disk
that will take the wear and tear of swaping?
2	Is swap size relevant to ram, should it be equal, greater, smaller?
Advantages disadvantages?  I rarely see in a workstation and my/our use
anywhere close to 4GB being used, it usually maxes out around 2,5GB. No,
no killing games here, maybe some chess and gnubg. Is it that a Ram of
1GB would benefit from 2-4GB swap space while with 16GB or Ram swap
would never be used?

3	chmod 600 for the swapfile.  Why?
4	Is "dd bs=1M count=4M" that defines the 4,000Mb of space/size of the file?

I am now going to use gnubg to test my mem capabilities.  I think making
it calculate best move 4-5 moves ahead in bg or chess will stress the
system out :)

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#    Create an empty file (1K * 4M = 4 GiB)
    sudo mkdir -v /var/cache/swap
    cd /var/cache/swap
    sudo dd if=/dev/zero of=swapfile bs=1K count=4M
    sudo chmod 600 swapfile

#    Convert newly created file into a swap space file.
    sudo mkswap swapfile

#    Enable file for paging and swapping.
    sudo swapon swapfile

#    Verify by: swapon -s or top:
top -bn1 | grep -i swap
#    KiB Swap:  4194300 total,  4194300 free

#    To disable, use
sudo swapoff swapfile.

#    Add it into fstab file to make it persistent on the next system
#    boot.
echo "/var/cache/swap/swapfile none swap sw 0 0" | sudo tee -a
   /etc/fstab

#    Re-test swap file on startup by:
    sudo swapoff swapfile
    sudo swapon -va
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-- 
 "The most violent element in society is ignorance" rEG