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I have some sensitive data in ram that i prefer not to be on disk. How do i disable swap? I have more then enough ram. If ram gets too high i have no problems with processes being terminated. How do I disable swap?

Note: I do not have a swap partition and this is running in a VM (VMWare)

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Even if you have a lot of RAM, it's not the best idea to completely work without swap (see for instance alexonlinux.com/swap-vs-no-swap ). Depending on your requirements you might consider putting the swap partition on a dm-crypt secured device, so that everything written to it will be encrypted. You have to make sure in such a case, that swap is enabled after encrypted volumes get available, and disabled before the device mapping is disabled, of course (I think that's default on Ubuntu, but I'm not sure). Just search the web for "encrypted swap" to find numerous guides. –  soulsource May 13 at 9:01

4 Answers 4

up vote 27 down vote accepted

Using

sudo swapoff -a  

is the usual way to turn off swap, with the swapon -a command used to turn it back on. See man swapoff for more information about turning off swap for explicit devices.

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This doesn't seem to persist across a reboot? –  ebyrob Apr 20 '13 at 2:31
6  
Permanent changes to swap are usually made in /etc/fstab. –  ubfan1 Apr 20 '13 at 5:51

If your concerned about the content of the swap partition you can always turn it off as specified in the usual way with sudo swapoff -a and then fill the swap partition with zeros or random data using dd.

First find your swap partition use Disks, Disk Utility, gparted (GUI) or the content of fstab to find it (cat /etc/fstab)

Having located it and double and triple checked it's location at say sda5 or some such issue the "disk destroyer" command (not to be used lightly)

sudo dd if=/dev/zero of=/dev/sda5

to blast it full of zeros or

sudo dd if=/dev/random of=/dev/sda5

to blast it full of random data.

The next time you turn swap on with

swapon -a

The system will happily use it again. If you have plenty of RAM you may not need swap at all. Issue the command

free when the system is under heavy load and see how much is in use to make this determination.

free

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You may disable swap after reboot by just commenting out the swap entry in /etc/fstab file. It will prevents swap partition from automatic mounting after a reboot.

sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

Now your swap entry on /etc/fstab will look like this,

#UUID=1dc65039-4ac4-xxxxx-xxx-4xxxxf96xxxx none            swap    sw              0       0
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Go into terminal and execute this command: gnome-disks. It is not installed in all distributions. If so, follow the instructions printed to install it and try again. Look for a device with the word 'swap' on the left pane. It usually has a size the same as your physical memory. Click the square button to disable it. Authenticate this change with your root password.

Screenshot: http://imgur.com/Og6igqb

In the System Monitor application (gnome-system-monitor), you will see it reports the swap area as 'not available'. The swap area is disabled but not deleted. You can enable it easily again in the future. Deleting the swap space has caused my system no harm but you will create more work for yourself if you do decide you want it back (hibernation) in the future.

edit: to prevent it mounting at startup, you should go into the "Edit Mount Options..." in gnome-disks and uncheck "Mount at startup".

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1  
Do you think that this answers the users concern about having sensitive data on the swap partition? Can you tell us why? –  Elder Geek May 9 at 2:33
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The user's main point was asking how to disable swap. If you have sensitive data, you should be using pre-boot encryption ideally. –  user170544 May 9 at 3:28
    
I respectfully disagree. When I read the question the first sentence I come across is "I have some sensitive data in ram that i prefer not to be on disk." I believe this was his main concern which is why he started with it. Regardless, I believe I have covered every aspect of his question in my answer. Consider it a helpful example. –  Elder Geek May 9 at 11:11

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