The quicker way of getting the same file is by using the
fallocateprogram. This command creates a file of a preallocated size instantly, without actually having to write dummy contents.
We can create a 4 Gigabyte file by typing:
The prompt will be returned to you almost immediately. We can verify that the correct amount of space was reserved by typing:
sudo fallocate -l 4G /swapfile
ls -lh /swapfile
-rw-r--r-- 1 root root 4.0G Apr 28 17:19 /swapfileAs you can see, our file is created with the correct amount of space set aside.
Enabling the Swap FileRight now, our file is created, but our system does not know that this is supposed to be used for swap. We need to tell our system to format this file as swap and then enable it.
Before we do that though, we need to adjust the permissions on our file so that it isn't readable by anyone besides root. Allowing other users to read or write to this file would be a huge security risk. We can lock down the permissions by typing:
Verify that the file has the correct permissions by typing:
sudo chmod 600 /swapfile
ls -lh /swapfile
-rw------- 1 root root 4.0G Apr 28 17:19 /swapfileAs you can see, only the columns for the root user have the read and write flags enabled.
Now that our file is more secure, we can tell our system to set up the swap space by typing:
sudo mkswap /swapfile
Our file is now ready to be used as a swap space. We can enable this by typing:
Setting up swapspace version 1, size = 4194300 KiB no label, UUID=e2f1e9cf-c0a9-4ed4-b8ab-714b8a7d6944
We can verify that the procedure was successful by checking whether our system reports swap space now:
sudo swapon /swapfile
sudo swapon -s
Filename Type Size Used Priority /swapfile file 4194300 0 -1We have a new swap file here. We can use the
freeutility again to corroborate our findings:
total used free shared buffers cached Mem: 3953 101 3851 0 5 30 -/+ buffers/cache: 66 3887 Swap: 4095 0 4095Our swap has been set up successfully and our operating system will begin to use it as necessary.
Make the Swap File PermanentWe have our swap file enabled, but when we reboot, the server will not automatically enable the file. We can change that though by modifying the
Edit the file with root privileges in your text editor:
At the bottom of the file, you need to add a line that will tell the operating system to automatically use the file you created:
sudo nano /etc/fstab
Save and close the file when you are finished.
/swapfile none swap sw 0 0