One of the easiest methods to protect your applications from running into memory issues is by expanding the swap space on your server. In this guide, we'll walk through how to add a swap file to an Ubuntu system.
Step 1: Checking Swap Information
Before proceeding, it's important to verify whether your system already has swap space configured. You can do this using the swapon
command as shown below.
<code>$ sudo swapon --show</code>
If there’s no output returned, it means that your system currently doesn’t have any swap space enabled.
Another way to confirm this is by using the free
command.
<code>$ free -h</code>
As seen in the image above, there is no active swap detected.
Step 2: Checking Available Space on the Partition
Before creating a swap file, you should ensure that your disk has enough free space. Use the following command to check available space.
<code>$ df -h</code>
The root partition /
has sufficient space to proceed with creating a swap file.
Step 3: Creating a Swap File in Ubuntu
Now we’ll create a 1GB swap file named "swap.img"
in the root directory using the fallocate command. You may adjust the size based on your requirements.
<code>$ sudo fallocate -l 1G /swap.img $ ls -lh /swap.img</code>
From the result, we can confirm that the swap file has been created successfully with the desired size of 1GB.
Step 4: Enabling the Swap File in Ubuntu
To activate the swap file, first set its permissions so only the root user can access it.
<code>$ sudo chmod 600 /swap.img $ ls -lh /swap.img</code>
You can see that only the root user has read and write access now.
Next, format the file for swap usage and enable it.
<code>$ sudo mkswap /swap.img $ sudo swapon /swap.img</code>
Verify the availability of the new swap space using these commands:
<code>$ sudo swapon --show $ free -h</code>
As shown above, the swap file has been successfully activated and is now being used by the system.
Step 5: Mount the Swap File Permanently in Ubuntu
To ensure the swap file persists after reboot, you need to add it to the /etc/fstab
configuration file.
<code>$ echo '/swap.img none swap sw 0 0' | sudo tee -a /etc/fstab $ cat /etc/fstab</code>
Step 6: Tuning Swap Settings in Ubuntu
There are several performance-related settings you may want to tweak when using swap.
Adjusting the Swappiness Value
Swappiness controls how aggressively the system moves data from RAM to swap. The default value is 60, but for servers, a lower value like 10 is often better.
Check the current setting:
<code>$ cat /proc/sys/vm/swappiness</code>
Apply the change temporarily:
<code>$ sudo sysctl vm.swappiness=10</code>
To make it permanent, add this line to /etc/sysctl.conf
:
<code>vm.swappiness=10</code>
Adjusting the Cache Pressure Setting
The vfs_cache_pressure
parameter determines how aggressively the kernel caches inode and dentry information.
Check the current value:
<code>$ cat /proc/sys/vm/vfs_cache_pressure</code>
A value of 100 causes the system to drop cache too quickly. A better value might be 50:
<code>$ sudo sysctl vm.vfs_cache_pressure=50</code>
To keep this setting after reboot, add this line to /etc/sysctl.conf
:
<code>vm.vfs_cache_pressure=50</code>
Once done, save and close the file.
Step 7: Removing a Swap File in Ubuntu
If you ever need to remove the swap file, run the following commands:
<code>$ sudo swapoff -v /swap.img $ sudo rm -rf /swap.img</code>
Also, don’t forget to remove the corresponding entry from the /etc/fstab file.
That concludes our guide. We've demonstrated how to add a swap file to your Ubuntu system. If you have any questions or run into issues, feel free to leave a comment below.
The above is the detailed content of How to Increase Swap Memory in Ubuntu Linux. For more information, please follow other related articles on the PHP Chinese website!

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