I know how to create and use a swap partition but can I also use a file instead?
How can I create a swap file on a Linux system?
0
Add a comment
|
3 Answers
Let's start with the basic information, you should inspect what vm.swappiness is set, and if set wisely to a more acceptable value than 60, which is the default, you should have no problem. This command can be run as normal user:
sysctl vm.swappiness
For instance, I have 32 GB RAM server with 32 GB swap file with vm.swappiness = 1. Quoting the Wikipedia:
vm.swappiness= 1: Kernel version 3.5 and over, as well as Red Hat kernel version 2.6.32-303 and over: Minimum amount of swapping without disabling it entirely.
In this example, we create a swap file:
32 GiB in size;
Located in
/(the root directory).
Change these two things accordingly to your needs.
Open terminal and become
root(su); if you havesudoenabled, you may also do for examplesudo -i; seeman sudofor all options):sudo -iAllocate space for the swap file,
-lis the same as--lengthon most systems, and-vis--verbose, more importantly theGmeans GiB, do not write GB, as it would mean 1000*1000 multiples:fallocate -v -l 32G /swapfileNote: DON'T use
ddas I found out for Hibernation a contiguous file is needed. (Unclear if also needed for swapping. May need adding some link to docs.)dd if=/dev/zero of=/swapfile bs=1G count=8 status=progressIf your
dddoes not supportstatus=progress, just leave it out.Note, that the size specified here in
Gis in GiB (multiples of 1024).
!!! This answer could change my point of view, I'll read it later: https://askubuntu.com/a/1017312/436624Change permissions of the swap file, so that only
rootcan access it:chmod 600 /swapfileMake this file a swap file:
mkswap /swapfileEnable the swap file:
swapon /swapfileVerify, whether the swap file is in use:
cat /proc/swapsOpen a text editor you are skilled in with this file, e.g.
nanoif unsure:nano /etc/fstabTo make this swap file available after reboot, add the following line:
/swapfile none swap sw 0 0
answered Oct 26, 2015 at 21:47
Vlastimil Burián
31.1k66 gold badges210 silver badges358 bronze badges
$ sudo dd if=/dev/zero of=/swapfile bs=1024 count=1048576
$ sudo chmod 600 /swapfile
$ sudo mkswap /swapfile
$ sudo swapon /swapfile
Note: you may sometimes use fallocate instead of dd:
$ sudo fallocate -l 1G /swapfile
— but with certain filesystems it may result in a file with holes which is unsuitable to act as a swap file.
Please check the script for creating a SWAP Memory of 16GB:
#!/bin/bash
#find Free
free -h
#Checking availability space
df -h
#swap Off
sudo swapoff /swapfile
#Allocate swap
sudo fallocate -l 16G /swapfile
#correct amount of space was reserved
ls -lh /swapfile
#file only accessible to root
sudo chmod 600 /swapfile
#amount of space was reserved for the root
ls -lh /swapfile
#now mark the file as swap space
sudo mkswap /swapfile
#Swap On
sudo swapon /swapfile
#swap Show
sudo swapon --show
#statment
echo -e "\n\n Swap 16Gb done"
