How can I turn off swap permanently?

Question

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. — animaletdesequia, Mar 29 '14 at 15:07
Simply put swapoff -a in /etc/rc.local and forget about that... ;) — user264467, Apr 02 '14 at 06:00
@user264467: it is quite counterintuitive to leave swap enabled just to disable it on every reboot, it is much cleaner to disable it permamently. — karatedog, Dec 12 '16 at 07:42

terdon · Answer 1 · 2014-06-12T17:19:34.347

145

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:

sudo nano /etc/sysctl.conf

And add this line to it:

vm.swappiness=10

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.

edited Jun 12 '14 at 17:19

answered Mar 28 '14 at 15:00

terdon

100,812

I love changing swappines, and I've not done in years. Thanks for the reminder. sudo upvote turdon! – Darth Egregious Mar 28 '14 at 17:18
23

Just to add to the 'safer approach' argument: When you have no swap and the system runs out of memory, the Linux OOM (Out Of Memory) killer is invoked. This selects a process based on a 'badness' score and then... kills it (terminates, closes) with no chance for the application to save its changes, clean up, etc. Thus, if you turn off swap and run out of memory, you very well run the risk of losing work if important processes score poorly in the OOM killer's eyes. So, you should only turn swap off if you are confident that you will never run out of memory. – Reid Mar 28 '14 at 21:21
7

@Reid worth pointing out that, obviously, the same exact thing will happen if you run out of swap space too. – o0'. Mar 28 '14 at 23:41
What if I change swap to 0? How would that turn out? 0 means it won't use swap unless absolutely necessary right? – Alex Li Mar 29 '14 at 19:31
@AlexLi no, 10 already means that. With 10 you will see next to no swapping. Setting it to 0 is not a good idea, seriously, swapping can really save you at times and setting a low swappiness value will solve your issue without making the system unstable. I have not tested this, but presumably, setting to 0 will disable swapping and bring all the problems associated with a lack of swap. – terdon Mar 29 '14 at 19:33
17

This does not actually answer the question. Disabling swap altogether can make a lot of sense on a system with 16GB or 32GB of RAM. A few extra GB of swap will not do any good in the case of memory-eating applications, while a large amount of swap (e.g. 20GB) would take up a lot of harddrive/SSD space. Also, hibernating with 32GB of RAM is not fun. – jmiserez Mar 29 '14 at 22:19
@jmiserez 1) my answer was posted after the two answers here that give a way to ignore the swap partition, that's why I started it with "may I offer an alternative?". 2) Actually, a few gigs of swap can make all the difference in the world, the system usually gets noticeably slower when swapping and one or 2 gigs may well give you enough time to kill the offending process and not deal with the OOM. 3) None of these approaches get your swap partition back so your point about HDD space is irrelevant. 4) I didn't even mention hibernation. – terdon Mar 30 '14 at 18:07
& 2) Fair enough. 3) It's easy to reclaim the space using gparted, once swap is disabled. 4) On Ubuntu, hibernation uses the swap partition, so the two share a common fate. 5) FYI: You can also use the zram-config package to enable memory compression once RAM runs out. That should also give you some breathing room runaway processes.

jmiserez

Mar 31 '14 at 05:38

Since I have put a 512GB SSD (almost 3 years ago) into my notebook, I have set it up without any Swap partition. First I had 8GB of RAM, now I have 16GB. I actually never had a problem plus I do not want to waste my SSD space with SWAP and hibernation... – Consumology Apr 02 '14 at 11:47

12

For some setup, as soon as you run out of physical RAM and starts swapping, the system starts "sucking mud" and becomes unusable. Yes, in theory you can get in and kill the offender, but when it takes 20+ minutes to change focus in the UI and even longer to get a password prompt via SSH, the OOMing ends up being the best option (followed by a hard reboot, followed by getting in and fixing the problem). – BCS Aug 12 '14 at 17:35

@BCS From my experience, the system usually will start "sucking mud" when there is not enough or no swap space available; what happens is, the system will get stuck in a continuous loop paging the hard drive for available swap space that does not exist and so will never be found. I've fixed this problem in the past by returning swappiness back to 60 and increasing the size of the swap partition; you see, "sucking mud" is exactly what swappiness prevents. – mchid May 03 '15 at 02:23

1

@mchid In most of the cases where I've had this problem, it was caused by a massive over commitment (e.g. a bug causes my project to allocate an use few dozen GB more than I have free). While in theory this might eventual work through, it takes so long that I am unwilling to wait and am forced to reboot the system. What I want is a solution that will have a chance of recovering with out the reboot. Practically, this requires OMM killing the correct offender. – BCS May 12 '15 at 22:50

2

@mchid Your suggested solutions aren't feasible when the UI is so frozen up that changing Windows takes 5 minutes, and waiting for command execution takes 10 minutes. It takes long enough if you know exactly what you are doing, but if you have to run several commands to find the worst memory offender, you can multiply that time by 3. For example, your drop_caches command creates 3 processes (echo, sudo, tee), which can take ages when your system is swapping.

I am not kidding, btw. My swap is on a slow hard drive and recovering from OOM without a hard reboot takes about an hour.

– fat-lobyte Sep 02 '16 at 09:07

2

@mchid My "solution" to the problem is turning off swap. Personally, I'd rather have processes crashing on me than a completely locked system. "if your system is swapping, you shouldn't have any problem", that's my point: I do have problems and lots of them. ZRAM was a nice idea back in the day, but in practice it turns out to do more harm than good.

And "run the command before you run into trouble" requires me to constantly keep an eye on system memory. That's not how I or most people use a computer, and they shouldn't. The device serves me, not the other way around.

– fat-lobyte Sep 13 '16 at 10:08

1

@mchid, I absolute agree with fat-lobyte, unfortunately. I have a fast SSD for swapping space, but it still takes ages and is unusable; this happens due to my faulty code. I prefer strongly to kill the system and reboot as well. We're both not offering a better solution, however, the killing is a better solution then swapping; the latter takes 30 minutes on my machine as well (until OOM killing processes are invoked). It's a nightmare. – Mayou36 Nov 02 '20 at 20:02

1

@mchid please stop having long conversations in the comments. Take it to chat or anywhere else that doesn't ping me. – terdon Nov 03 '20 at 08:54

score 57 · Answer 2 · edited May 17 '14 at 11:41

57

Find the line in /etc/fstab referring to swap, and comment it. Mine is like this:

UUID=6880a28d-a9dc-4bfb-ba47-0876b50e96b3 /               ext4    errors=remount-ro 0       1
UUID=7350e6f2-e3a7-4d80-9a95-8741c7db118f /home           ext4    defaults        0       2
UUID=E2E26AD1E26AAA0D /media/windows  ntfs    defaults,umask=007,gid=46 0       0

# Swap a usb extern (3.7 GB):
#/dev/sdb1 none swap sw 0 0

You can edit this file with gedit. Backup it first, just in case:

sudo cp /etc/fstab /etc/fstab_backup
gksu gedit /etc/fstab

Just add # to the beginning of the line where swap is, and reboot the computer.

OR

Try Command-line way of commenting out swap entry in /etc/fstab file,

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

edited May 17 '14 at 11:41

Avinash Raj

78,556

answered Mar 28 '14 at 14:10

animaletdesequia

8,354

I get this when I type gksu gedit /etc/fstab `# /etc/fstab: static file system information.

Use 'blkid' to print the universally unique identifier for a

device; this may be used with UUID= as a more robust way to name devices

that works even if disks are added and removed. See fstab(5).

/host/ubuntu/disks/root.disk / ext4 loop,errors=remount-ro 0 1 /host/ubuntu/disks/swap.disk none swap loop,sw 0 0`
– Alex Li Mar 28 '14 at 14:27
1

So, do what he's saying. Comment out the first line that refers to "swap". :P – cHao Mar 29 '14 at 02:42

score 41 · Answer 3 · edited Dec 09 '20 at 16:40

41

Wrong.. if systemd finds a SWAP partition on any drive it will anyway automount it. Strange that nobody mentioned systemd. The solution is quite simple anyways; to permanently disable swap you must:

swapoff -a
edit /etc/fstab and comment any swap entries if present (you might be able to skip this step 2, and step 3 without step 2 may work for you).
run: sudo systemctl mask "dev-sdXX.swap" (where XX is the swap partition. Note, you should use quotes around the unit name in case the name has escape characters/backslash. Also useful to do it for all possible partitions so that if there is a swap partition on any other drive it will not be mounted.)

Peace out.

edited Dec 09 '20 at 16:40

trusktr

162

answered Dec 09 '17 at 19:58

Zibri

739

3

number 3 for the win!! – oneklc Oct 09 '19 at 21:55
1

Number 3 is essential for Ubuntu 18.04 or maybe because of the transition from 16.04->18.04 and/or maybe because of the installation on nvme. – vigilian Nov 05 '19 at 09:28
Do we have the opposite command just to know ? – vigilian Nov 05 '19 at 09:29
3

sudo systemctl unmask dev-sdXX.swap – tgwaste Jan 22 '20 at 02:44

mdalacu · Answer 4 · 2014-03-29T09:30:52.863

18

Just delete the entry (or comment it using # in front of the line) from fstab and reboot. Look for the line with the word "swap" in it.

sudo nano /etc/fstab

edited Mar 29 '14 at 09:30

answered Mar 28 '14 at 14:10

mdalacu

670

12

This one would work too, but I think is better commenting the line rather than removing it completely, just in case you want to revert the changes. – animaletdesequia Mar 28 '14 at 14:11
1

I have edited my post. – mdalacu Mar 29 '14 at 09:31

score 6 · Answer 5 · edited Nov 22 '20 at 05:59

Complementing Zibri's answer:

swapoff -a will disable all swaps temporarily.
If you have some swaps in /etc/fstab, just comment them out and reboot.
In my case (OdroidMC1+Armbian), the swap is controlled by systemctl. To find the responsible, use systemctl --type swap.

Example:

# systemctl --type swap
UNIT           LOAD   ACTIVE SUB    DESCRIPTION

dev-zram1.swap loaded active active /dev/zram1
LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.
1 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

Disable by masking it with sysctl:

# systemctl mask dev-zram1.swap
Created symlink /etc/systemd/system/dev-zram1.swap → /dev/null.

Thanks for your contribution! Please note that because we use a Q&A format, you can't reply to other answers or comments. It's best to try write your answer in a way that doesn't require referencing another answer since existing answers can be modified. It can also be confusing to follow two answers that might be in conflict with one another. If you need to reference other content, make sure that you use a permalink since usernames can also change over time. — Nmath, Nov 22 '20 at 06:02

Benny · Answer 6 · 2022-09-21T20:39:09.487

3

Disable Swap Permanently

swapoff -a                 # Disable all devices marked as swap in /etc/fstab
sed -e '/swap/ s/^#*/#/' -i /etc/fstab   # Comment the correct mounting point
systemctl mask swap.target               # Completely disabled

Note: All Commands Should Run with Root Privileges

edited Sep 21 '22 at 20:39

answered Apr 05 '22 at 21:43

Benny

4,920

How can I turn off swap permanently?

6 Answers6

Use 'blkid' to print the universally unique identifier for a

device; this may be used with UUID= as a more robust way to name devices

that works even if disks are added and removed. See fstab(5).

Disable Swap Permanently

Linked

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