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I've deleted my existing swap partition due to some partitioning problem. I don't have a swap space now so I've created a swap file with:

dd if=/dev/zero of=/root/myswapfile bs=1M count=1024

Here's after swapon -s :

/root/myswapfile    file    1048572    1320    -1

Now I want to edit my /etc/fstab to enable the swap file after reboot. Please tell me how to edit my fstab file.

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Notice that bs=1G count=1 would give the same result, have a look at the dd manpage for the other units. –  LiveWireBT Dec 20 '14 at 6:02

2 Answers 2

These ares the steps to create a swap on a file:

sudo mkdir -p /var/cache/swap/   # create a driectory that holds the swap file
sudo dd if=/dev/zero of=/var/cache/swap/myswap bs=1M count=4096 # for 4 GByte
sudo chmod 0600 /var/cache/swap/myswap # only root can access
sudo mkswap /var/cache/swap/myswap # format as swap
sudo swapon /var/cache/swap/myswap # announce to system

Insert the following line in /etc/fstab for swap from the next boot:

/var/cache/swap/myswap    none    swap    sw    0   0

Note: In case you have your system files on a SSD you may want to consider to hold your swap file on a hard disk location.

Also note: You can not use a swap file for hibernation (see Ubuntu SwapFaq)

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Why wouldn't you want your swap on the SSD as well? –  Joseph Garvin Sep 22 '12 at 4:25
@JosephGarvin: as wear-out may probably not be a problem you still waste a lot of (expensive) disk space when having swap on SSD. Depending on your system RAM you may not need swap too often. askubuntu.com/questions/178661/do-i-need-swap-with-new-ssd –  Takkat Sep 22 '12 at 7:00

Swap on SSD is dangerous cause SSD drives have low duration on intense write operations.

This means you can really consume your precious and expensive SSD drive like that.

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