[How To] configure swap partition in Ubuntu 19.10

RAM is very important for the computer normal operation. It contains all data of the working programs. When the memory is full, the program may produce various errors or even stop working. The response time of the system increases so much that it becomes impossible to work with it.

The easiest way to increase the amount of RAM and protect the system from memory overflow is to add a swap partition. This article will show how to configure swap on Ubuntu 16.04. We will consider the option of adding a swap partition for regular computers, as well as a swap file for servers.

The content of the article

• Note
• What is Swap?
• Check Swap
• Setting up the paging file
• Check disk space
• Creating a paging file
• Swap activation
• Permanent swap file
• Setting up a swap partition in Ubuntu
• Additional settings
• Conclusion

Note

Swap partition is on the HDD, using this method for SSDs can cause problems. As SSD has a limited number of overwrites of one sector then it will reduce the life of your disk. Therefore, the use of swap space on the SSD is strictly not recommended.

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What is Swap?

Swap is an area on the hard disk that is used to temporarily store data of main memory if there is no more free space. This allows you to increase the amount of information that the system can store in working memory. The swap space is used only when the memory is already fully occupied, and only data that has been used for a long time will be placed there.

Working with data stored in swap will be much slower than in RAM, but the operating system will continue to work and use swap only for old data. In general, this can be an excellent protection against memory overflow. The paging space can be configured in two ways by adding a ubuntu swap partition to disk or creating a paging file.

Check Swap

Before staring configuration, let’s see if other paging partitions are exist in the system. To do this, run:

$ sudo swapon --show

If nothing is displayed, then swap is not configured on your system. You can also make sure that there is no active swap using the free utility:

$ free -h
total        used        free      shared  buff/cache   available
Mem:          3.8Gi       1.6Gi       154Mi       3.0Mi       2.1Gi       2.0Gi
Swap:            0B          0B          0B

Swap line is empty, so the swap partition is not yet connected.

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Setting up the paging file

Servers often use a paging file, this method is used because it is not always possible to change the disk partition layout.

Check disk space

First let’s make sure that the disk has enough free space. The easiest way to find the free space in the terminal is the df command:

		$ sudo df -h
		Filesystem      Size  Used Avail Use% Mounted on
		udev            1.9G     0  1.9G   0% /dev
		tmpfs           393M  1.6M  391M   1% /run
		/dev/sda1        20G  9.1G  9.6G  49% /
		tmpfs           2.0G     0  2.0G   0% /dev/shm
		tmpfs           5.0M  4.0K  5.0M   1% /run/lock
		tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup
		/dev/loop0      4.2M  4.2M     0 100% /snap/gnome-calculator/406
		/dev/loop1       90M   90M     0 100% /snap/core/6673
		/dev/loop2      152M  152M     0 100% /snap/gnome-3-28-1804/36
		/dev/loop3       54M   54M     0 100% /snap/core18/941
		/dev/loop4      1.0M  1.0M     0 100% /snap/gnome-logs/57
		/dev/loop5       43M   43M     0 100% /snap/gtk-common-themes/701
		/dev/loop6      141M  141M     0 100% /snap/gnome-3-26-1604/70
		/dev/loop8       54M   54M     0 100% /snap/core18/782
		/dev/loop7      141M  141M     0 100% /snap/gnome-3-26-1604/82
		/dev/loop9      3.8M  3.8M     0 100% /snap/gnome-system-monitor/70
		/dev/loop10      92M   92M     0 100% /snap/core/6531
		/dev/loop11     141M  141M     0 100% /snap/gnome-3-26-1604/74
		/dev/loop12      15M   15M     0 100% /snap/gnome-characters/254
		/dev/loop13     1.0M  1.0M     0 100% /snap/gnome-logs/61
		/dev/loop16      15M   15M     0 100% /snap/gnome-characters/206
		/dev/loop17     4.2M  4.2M     0 100% /snap/gnome-calculator/352
		/dev/loop18     3.8M  3.8M     0 100% /snap/gnome-system-monitor/77
		/dev/loop21     152M  152M     0 100% /snap/gnome-3-28-1804/31
		/dev/loop22      15M   15M     0 100% /snap/gnome-logs/45
		/dev/loop23     2.3M  2.3M     0 100% /snap/gnome-calculator/260
		/dev/loop24      36M   36M     0 100% /snap/gtk-common-themes/1198
		tmpfs           393M   16K  393M   1% /run/user/123
		tmpfs           393M     0  393M   0% /run/user/1000
		/dev/loop25      54M   54M     0 100% /snap/core18/970
		/dev/loop26      90M   90M     0 100% /snap/core/6818
		/dev/loop15      15M   15M     0 100% /snap/gnome-characters/258
		/dev/loop27     3.8M  3.8M     0 100% /snap/gnome-system-monitor/81
		/dev/loop28     152M  152M     0 100% /snap/gnome-3-28-1804/40			

In our case there is enough space on/dev/sda1 partition to accommodate paging space. The size of the swap Ubuntu 16.04 depends on your needs. Usually it is recommended to use the amount of two times the actual size of the RAM. But more than 4 GB is not needed. If you plan to use hibernation on a personal computer, then you need to use a volume equal to the amount of RAM.

Creating a paging file

The fastest way to create a swap file ubuntu is such a file, it is to use the fallocate utility, it creates the file of the desired size instantly. Let’s assume that we have 1 GB of RAM, we’ll add a 2 GB ubuntu swap partition. To do this, run:

sudo fallocate -l 1G /swapfile

See if the right amount of memory is really reserved:

$ls -lh /swapfile
-rw-r--r-- 1 root root 1.0G May 22 10:56 /swapfile

Swap activation

When the file is ready, we need to turn it into a Ubuntu swap file. First you need to block access to it by everyone except the superuser. To do this, run:

sudo chmod 600 /swapfile

Now only root can read and modify this file:

ls -lh / swapfile

Then create the swap file system with the command:

sudo mkswap /swapfile

You can make sure that everything works with the command:

sudo swapon --show

One more time let’s check disk free space:

free -h

As you can see, the paging file was successfully created and activated. Now the memory is much more and the system will not freeze. But it will only work until the reboot.

Permanent swap file

As we said, this swap will only work until the server or computer is rebooted. To configure the Swap Ubuntu 16.04 to be saved after the reboot, you need to edit the /etc/fstab file. You can manually add a line to the file, but you can use the following command:

 echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

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Setting up a swap partition in Ubuntu

For configureint swap as a partition all actions are similar to those used for a file, only a section is used instead of a file. Suppose we want to use the /dev/sda2 partition. First create a Ubuntu swap from a regular partition:

 sudo mkswap /dev/sda2

Then activate the swap partition:

sudo swapon /dev/sda2

Check if everything went right:

sudo swapon --show

If yes, then you will see the necessary one in the list of connected partitions. It remains to add the line in /etc/fstab for automatic activation after a reboot:

echo '/dev/sda2 none swap sw 0 0' | sudo tee -a /etc/fstab

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Additional settings

You can control the amount of swap space usage in Ubuntu using the swappiness kernel parameter:

cat /proc/sys/vm/swappiness
60

The default value is 60. If this value is closer to 100, the system will try to put more data into the paging and save memory, with values close to zero, the kernel does not transfer data to disk unless it is absolutely necessary. This option can make the system faster, especially for home computers.

To set the swappiness value to 70 run:

 
sudo sysctl vm.swappiness=70
vm.swappiness = 70

Another parameter that affects the amount of memory used is vfs_cache_pressure. It tells the system how long it is necessary to keep open files in the RAM cache. A value of 100 causes the system to delete such files very quickly, 0 – to keep them in memory as long as possible. See current status:

cat /proc/sys/vm/vfs_cache_pressure
100

To keep files longer, you can set the value to 50:

		sudo sysctl -w vm.vfs_cache_pressure=50
		vm.vfs_cache_pressure = 50		

Conclusion

This guide will help you temporarily solve the problem with paging space if the server does not have enough memory, or it can help prevent the computer from hanging. Setting up swap Ubuntu is very easy. If you have any questions, ask in the comments!

Source

losst.ru