8. swap

In our previous example, I showed you how to see your partition table. Let's revisit that example, more specifically this line:

Number  Start   End     Size    Type      File system     Flags
 5      6861MB  7380MB  519MB   logical   linux-swap(v1)

What is this swap partition? Well, swap is what we use to allocate virtual memory to our system. If you are low on memory, the system uses this partition to "swap" pieces of memory of idle processes to the disk, so you're not bogged down for memory.

Using a partition for swap space

Let's say we wanted to set our partition /dev/sdb2 to be used for swap space.

1. First, make sure we don't have anything on the partition.
2. Run: mkswap /dev/sdb2 to initialize swap areas.
3. Run: swapon /dev/sdb2. This will enable the swap device.
4. If you want the swap partition to persist on bootup, you need to add an entry to the /etc/fstab file. sw is the filesystem type that you'll use.
5. To remove swap: swapoff /dev/sdb2.

Generally, you should allocate about twice as much swap space as you have memory. However, modern systems today are usually powerful enough and have enough RAM as it is.