Allocate swap after Ubuntu 14.04 LTS installation

Question

I've installed Ubuntu 14.04 LTS about one month ago, I'm dual booting Ubuntu 14.04 LTS and Windows 8.1.

I didn't create any swap space while installation but now I really need to add this for Ubunutu. I tried checking for any assigned swap space by using sudo swapon -s and I got empty headers like shown below:

ahsan@ahsan-Inspiron-N5110:~$ sudo swapon -s
Filename                Type        Size    Used    Priority

Then I tried to allocate some swap space using dd of=output.dat bs=1 seek=390143672 count=0 and the output was:

0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000170607 s, 0.0 kB/s

I also tried the command sudo dd if=/dev/zero of=/swapfile bs=1G count=4 and output was:

dd: memory exhausted by input buffer of size 1073741824 bytes (1.0 GiB)

Then I tried sudo fallocate -l 4G /swapfile but output was:

fallocate: /swapfile: fallocate failed: Operation not supported

I aslo checked my hard drives following is my hard drive structure:

ahsan@ahsan-Inspiron-N5110:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        99G   18G   77G  19% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
udev            1.4G  4.0K  1.4G   1% /dev
tmpfs           286M  1.2M  284M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            1.4G   24M  1.4G   2% /run/shm
none            100M   56K  100M   1% /run/user

And the output of free -m is:

ahsan@ahsan-Inspiron-N5110:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          2850       2665        184        421         25        846
-/+ buffers/cache:       1794       1055
Swap:            0          0          0

Please show me how can I add the swap without affecting any data of mine. I've installed 64 bit Ubuntu LTS and have 3GB of RAM and a 500GB hard drive.

I have been to this Ask Ubuntu question and I tried the commands and the output is:

ahsan@ahsan-Inspiron-N5110:~$ sudo dd if=/dev/zero of=/swapspace bs=1G count=4
4+0 records in
4+0 records out
4294967296 bytes (4.3 GB) copied, 47.1951 s, 91.0 MB/s
ahsan@ahsan-Inspiron-N5110:~$ sudo dd if=/dev/zero of=/swapspace bs=1G count=4sudo mkswap /swapspace
dd: invalid number ‘4sudo’
ahsan@ahsan-Inspiron-N5110:~$

Exactly what you want to fix? "memory exhausted by input buffer", fallocate? — Braiam, Dec 30 '14 at 05:52
The clue was in the error message dd: invalid number '4sudo', right? I would guess you had a copy/paste problem. Glad you got your problem solved! In the future, read those error messages carefully and try to figure out why you're getting that message!;-) Good luck. — shellter, Jan 07 '15 at 16:15

Ben Grimm · Accepted Answer · 2015-04-30T16:30:18.637

53

First, to create 4,000 MB of swap space:

$ sudo dd if=/dev/zero of=/swapspace bs=1M count=4000
4000+0 records in
4000+0 records out
4194304000 bytes (4.2 GB) copied, 5.92647 s, 708 MB/s

or

$ sudo fallocate -l 4000M /swapspace

Next turn it into a usable swap file:

$ sudo mkswap /swapspace
Setting up swapspace version 1, size = 4095996 KiB
no label, UUID=7d1895e4-7ccf-42c6-979a-51ebddb49e91

Activate it:

$ sudo swapon /swapspace

Confirm active swap spaces:

$ cat /proc/swaps
Filename                Type        Size    Used    Priority
/swapspace              file        4095996 0       -1

Next, add the following line to /etc/fstab to activate the new swap at boot:

/swapspace none swap defaults 0 0

See also this wiki page: https://help.ubuntu.com/community/SwapFaq

edited Apr 30 '15 at 16:30

answered Dec 29 '14 at 20:00

Ben Grimm

1,420

edited the question can you please have a look – Ahsan Hussain Dec 29 '14 at 20:11
sorry i mistakenly tried to run command twice, i think its worked for me :) now also showing swap in system monitor.. Thanks alot – Ahsan Hussain Dec 29 '14 at 20:14
i restarted the machine and the swap is gone, its again not available – Ahsan Hussain Dec 29 '14 at 20:18
1

The "running out of memory" part should be added to the answer. Comments are meant to be transient, they may be deleted. – Alexia Luna Dec 30 '14 at 11:52
1

sudo apt-get install swapspace is best option compare to allocating like this? – LOG_TAG Sep 27 '16 at 21:07

score 6 · Answer 2 · answered Jan 07 '15 at 16:05

To answer your question indirectly, you don't need to manage swapfiles yourself. There is a package called swapspace which will dynamically add swap files as needed.

sudo apt-get install swapspace

Then you are done. Your system will grow and shrink swap space as needed.

score 5 · Answer 3 · answered Dec 29 '14 at 20:21

5

Follow these steps:

sudo dd if=/dev/zero of=/mnt/{filename}.swap bs=1M count={swap_size}
sudo mkswap /mnt/{filename}.swap
sudo swapon /mnt/{filename}.swap
sudo gedit /etc/fstab
Add the following text at the end of the file, /mnt/{filename}.swap none swap sw 0 0

Note: Replace {filename} with any name you want to set to the file and replace {swap_size} with the size you want to assign to the swap file. Be sure the size of the file must the twice larger than the memory size.

answered Dec 29 '14 at 20:21

Wolverine

654

2

"Be sure the size of the file must the twice larger than the memory size." That advice no longer holds nowadays unless you're really low on memory (say, 1 GB or less). If you want to use hibernation, you'll need at least the amount of physical memory as swap, but there's no reason to have 8 GB swap if you have 4 GB RAM. – Alexia Luna Dec 30 '14 at 11:54
Your suggestion is considered. – Wolverine Dec 30 '14 at 11:58

Allocate swap after Ubuntu 14.04 LTS installation

3 Answers3

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