Linux turn off swap

Best way to disable swap in Linux

I am running a custom compiled 3.18.9 kernel and I am wondering about the best way to disable swap on the system. I also use init if it makes a difference. Is it enough to comment or remove the swap line in /etc/fstab to prevent swap from working/mounting at boot or should I recompile the kernel without Support for paging of anonymous memory (swap) to be 100% sure it does not get enabled? I run encrypted partitions and want to prevent accidental leakage to the hard disk. My system specifications are also great enough that I can survive in a swap-less environment.

@MichaelHampton I didn’t see a need at the point in time until I realized what was eventually going to happen. Plus my system doesn’t reach a point in any time that the swap was used, so I feel I am free to remove it.

I’d remove the feature from the kernel then. Otherwise someone can plug an USB-stick and start swapping to it again.

@ott Doesn’t the user require super user access to use the swapon/swapoff executable? I might disable it again just in case, but I am uncertain a unprivileged user can create swap files.

@ott— this is for a laptop so I will be in control of it 24/7. If someone has gotten physical access to it or managed to exploit it to gain access to my unprivileged users there would be worse problems than worrying about a swap file being created. Thanks for the clarification though!

7 Answers 7

1. Identify configured swap devices and files with cat /proc/swaps .
2. Turn off all swap devices and files with swapoff -a .
3. Remove any matching reference found in /etc/fstab .
4. Optional: Destroy any swap devices or files found in step 1 to prevent their reuse. Due to your concerns about leaking sensitive information, you may wish to consider performing some sort of secure wipe.

On some systems you must also rebuild the initrd archive, e.g. with dracut —regenerate-all —force or mkinitrd , or the system will not boot. Thanks to J.O. Aho and Carlos E.R. on alt.os.linux.suse .

This doesn’t solve it for me, the system boots every time with swap enabled, even though there’s no fstab entry for it. It’s incredibly annoying.

It used to be that only swap partitions in /etc/fstab were used automatically, however, systemd may be changing that slightly. You might need to do:

systemctl mask dev-sdXX.swap 

(change sdXX) to your real formatted swap partition, which, begs the question of why you have a swap partition if you don’t want it used.

If you are not using systemd, then, removing the swap entries from /etc/fstab should be sufficient (as far as I know).

Maybe the real solution is to get rid of the swap partitions, so they won’t be used accidentally. To remove the swap partitions, I would use fdisk to change the partition type from swap to something else, and then reformat the partition or use: dd if=/dev/zero of=/dev/old-swap-partition in order to zero it out and prevent its use.

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How to Permanently Disable Swap Partition in Linux

Swapping or swap space represents a physical memory page that lives on top of a disk partition or a special disk file used for extending the RAM memory of a system when the physical memory fills up.

Using this method of extending RAM resources, inactive memory pages are frequently dumped into the swap area when no RAM is available. However, due to the spinning speed of classical hard disks, swap space is way lower in transfer speeds and access time compared to RAM.

On newer machines with fast SSD hard disks, reserving a small partition for swapping can greatly improve access time and speed transfer compared to classical HDD, but the speed is still magnitudes lower than RAM memory.

Some suggest that the swap space should be set as twice the amount of machine RAM. However, on systems with more than 4 GB of RAM, swap space should be set between 2 or 4 GB.

In case your server has sufficient RAM memory or does not require the use of swap space or the swapping greatly decreases your system performance, you should consider disabling the swap area.

How to Check Swap Space in Linux

Before actually disabling swap space, first, you need to visualize your memory load degree and then identify the partition that holds the swap area, by issuing the below free command.

Look for the Swap space used size. If the used size is 0B or close to 0 bytes, it can be assumed that swap space is not used intensively and can be safely disabled.

How to Check Swap Partition in Linux

Next, issue following the blkid command, look for TYPE=»swap» line in order to identify the swap partition, as shown in the below screenshot.

Again, issue the following lsblk command to search and identify the [SWAP] partition as shown in the below screenshot.

How to Disable Swap in Linux

After you’ve identified the swap partition or file, execute the below command to deactivate the swap area.

# swapoff /dev/mapper/centos-swap

Or disable all swaps from /proc/swaps, which provides a snapshot of the swap file name.

Run free command in order to check if the swap area has been disabled.

How to Disable Swap Permanently in Linux

In order to permanently disable swap space in Linux, open /etc/fstab file, search for the swap line and comment on the entire line by adding a # (hashtag) sign in front of the line, as shown in the below screenshot.

Afterward, reboot the system in order to apply the new swap setting or issue mount -a command in some cases might do the trick.

After the system reboot, issuing the commands presented at the beginning of this tutorial should reflect that the swap area has been completely and permanently disabled in your system.

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I’am a computer addicted guy, a fan of open source and linux based system software, have about 4 years experience with Linux distributions desktop, servers and bash scripting.

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8 thoughts on “How to Permanently Disable Swap Partition in Linux”

I’ve been told that “swap space” is used during SUSPEND operations. I welcome someone to offer a robust explanation. It is important for road warriors and any who rely on laptop portability. During “sleep” [suspend to ram] current runtime details get written to swap before putting things on hold. During “hibernate” [suspend to disk] the majority of the system state gets written to swap before power off. Reply

The “free -h” commands must be executed when the system is under heavy load. Otherwise, it does not provide the information necessary to determine whether a swap partition or space is needed. When executed on an idling system, the command will only tell you the size of the swap partition and that it is not being used. It’s like running the “top” command on an idling system to see the CPU Load. It will show the CPU Load to be negligible. I agree with S. Daniels on the use of GParted. It not only provides a visual representation of your disks but also can delete your swap partition and recover that space by moving and/or resizing other partitions. Using the command line to accomplish your tasks may be ‘leet’ and cool but it is also dangerous to the health of your system. Using GParted prevents misspelling or use of incorrect CLI commands, as well as the use of incorrect options which can result in making the drive unusable. Reply

These instructions are rather outdated for any linux with a desktop:MATE, xfce, Gnome or KDE/Plasma. Firstly, the program Gparted very nicely displays swap size, location and UUID. “blkid”, especially on a dual-boot or system with multiple OSes is just going to display a lot of confusing and unhelpful entries. The KDE partitioner is inferior, but adequate. The centos-swap is fairly specific to CentOS Linux, this should be explained in the article. A swap file can also be used in place of a dedicated partition, this should also be mentioned. “Vi” is very much overkill for editing fstab. “Vim” is easier than “vi” for newbies in every case, and “pico /etc/fstab” or “nano /etc/fstab” are more appropriate here. Finally, for José , 30GB is seriously wrong. I suspect he somehow changed a data or system partition into a swap partition. He can “manage flags in Gparted” to inspect it for contents. I’m just a hobbyist, but have nearly 20 years experience, since a Debian bootable CD, the first Linux installation disk that did not need a floppy to boot, came out in 2000. Reply

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How to Permanently Disable Swap Partition in Linux

The swap partition or swap file in a Linux operating system acts as a temporary storage area on the hard drive, which the system uses when the physical memory (RAM) is full. It is used to swap out less used ‘pages’ of memory, so that the system does not run out of physical memory for running applications.

However, with the evolution of hardware technology and the affordability of RAM, most modern systems come with a substantial amount of memory. Therefore, some users might decide to disable the swap partition, particularly in situations where they have sufficient RAM, or they are running Linux on a solid state drive (SSD), where the lifespan could be affected by the constant read/writes of the swap partition.

Disclaimer: While disabling swap may seem like a good idea in some circumstances, be aware that it can lead to system instability, particularly if your system runs out of physical memory. Always ensure you have enough RAM to handle all running processes before proceeding.

Here’s how you can permanently disable swap in Linux.

Step 1: Turn off Swap

First, you need to turn off the swap space. This can be done immediately by using the `swapoff` command.

The ‘-a’ flag denotes ‘all’, meaning that all swap spaces are disabled.

Step 2: Backup the fstab File

Before making permanent changes to the system, it’s a good idea to back up the relevant configuration file—in this case, /etc/fstab. This file contains information about filesystems and is read by the system during boot-up. Here’s how you can make a backup:

sudo cp /etc/fstab /etc/fstab.bak 

Step 3: Edit the fstab File

Next, you need to edit the /etc/fstab file to remove the swap entry. You can use a text editor of your choice; nano, vim, or gedit are popular options. Here’s how to do this with nano:

In this file, find the line that looks something like this:

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How can I turn off swap permanently?

Swap makes my system all sluggish and turning it off makes everything smoother. I have 3.5 GB of RAM. I know how to turn swap off by entering sudo swapoff -a in the terminal, but that’s just for the current session, because after a reboot swap turns itself back on. Is there any way to turn swap off permanently?

Yes it is, but it still can be used. I have a little script that mounts the swap partition when the system goes into hibernation and un-mounts it when it comes back. The swap file doesn’t need to be active in the meantime.

@user264467: it is quite counterintuitive to leave swap enabled just to disable it on every reboot, it is much cleaner to disable it permamently.

6 Answers 6

May I suggest a safer approach? You never know when swap can save you from crashing. While swapping does indeed slow down your computer, if you use a program that eats up all your RAM, having the ability to swap can save you from a hard reboot. When the computer starts swapping, you’ll notice and be able to kill the offending application.

So, instead of disabling swap altogether, just make sure your OS swaps very rarely. This is controlled by the vm.swappiness setting in /etc/sysctl.conf . Ubuntu’s default setting is 60 if I remember correctly which is too much for most situations and will cause you to start swapping even while RAM is still available. If you reduce this value, you will be able to keep the safety line of swap while only using it for emergencies. So, open the file:

If that is still too much, change the 10 to 1. Now, after you restart, you will only swap when absolutely necessary and you can simply forget about it.

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