При покупке ВПС сервера часто не бывает включен SWAP файл. Подробная, рабочая инструкция по активации свап-файла.

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SWAP – один из механизмов виртуальной памяти, при котором отдельные фрагменты памяти (обычно неактивные) перемещаются из ОЗУ во вторичное хранилище (отдельный раздел или файл), освобождая ОЗУ для загрузки других активных фрагментов памяти.

A Swap file is simply a small amount of space created on a servers hard drive to simulate Ram. In the event that the server is running low on memory it will look at the hard drive and ease the load tricking the system to think it has more memory. We will set up the swap file on the hard drive to increase the performance of the server just a little bit more.

Begin by checking your resources to make sure we can add the file. When you run the following command you will see the percentage space on your Hard drive that is currently being used.

df -h

When creating a Swap file usually you want to add half of your existing RAM up to 4GB(If you have 1GB of actual Ram then you add a 512MB file). In this part I will be adding a 512MB swap file to the drive. The way that this is calculated is by 1024 x 512MB = 524288 block size.

sudo dd if=/dev/zero of=/swapfile bs=1024 count=524288

Now that we have added a swap file, a Swap file area needs to be created in order to proceed.

sudo mkswap /swapfile

With the Swap file created and the Swap file area added we can go ahead and add permissions to the file so that only the owner can read and write.

sudo chown root:root /swapfile
sudo chmod 0600 /swapfile

Now that the swap file has the appropriate permissions we can go ahead and activate the it.

sudo swapon /swapfile

You can verify your newly added Swap file with the following.

sudo swapon -s

In order to make the Swap file always active even after a reboot, we must configure it accordingly.

sudo vi /etc/fstab

Инструкция по работе с редактором vi

Paste the following command at the bottom of the file save your work and exit.

/swapfile              swap   swap     defaults     0 0

Finally, verify if your swapfile is activated by typing the following command:

free -m