Adding Linux swap file

1. Switch to the root account

2. Swap file is created, create a file 8G here
   dd if=/dev/zero of=/swapfile bs=1024 count=8388608
   where
   if = / dev / zero: reading data from / dev / zero file.
   of = / swapfile: file set here to create the swap file, the contents read from / dev / zero in.
   bs = 1024: each read and write 1024 BYTES.
   count = 8388608: number of blocks to be written, bs block sizes are provided. Calculated as the number of blocks of 1024 × 1024 × 8 = 8388608. The first is the size of bs of 1024, 1024BYTE, for the 1M. A second means 1024 1024 1M, as 1G. 8 The third refers to 8G.

3. Set permissions swap file. This step is for safety.
   chown root:root /swapfile
chmod 0600 /swapfile

4. The file format for the swap file
   mkswap /swapfile

5. Enable swap file
   swapon /swapfile

6. Let the system boot automatically enabled. Need to edit the /etc/fstabfile, add the following in this file:
   /swapfile swap swap defaults 0 0

• Disable swap file
  swapoff /swapfile
• Check swap file usage information
  swapon -s