Under some customized Linux OS, they may remove the swap file, if you want to add a swap file while login to the system, is that possible?
Obviously it is!
- Login as a root user. If you want to change some system settings, you must be a root user.
- Create a storage file. The following command creates a 2 GB file.
[[email protected] ~]# dd if=/dev/zero of=/swapfile bs=1024 count=2097152 2097152+0 records in 2097152+0 records out 2147483648 bytes (2 GB) copied, 12.23347 s, 166 MB/s
if=/dev/zero: Read from /dev/zero file. /dev/zero is a special file in that provides as many null characters to build storage file called /swapfile.
of=/swapfile: Read from /dev/zero write storage file to /swapfile.
bs=1024: Read and write 1024 BYTES bytes at a time.
count=2097152: Copy only 2097152 BLOCKS input blocks.
3. Secure the swap file. Setup correct file permission for security reasons, enter:
[[email protected] ~]# chown root:root /swapfile [[email protected] ~]# chmod 0600 /swapfile
- Set up a Linux swap area. Type the following command to set up a Linux swap area in a file:
[[email protected] ~]# mkswap /swapfile
- Enabling the swap file. Finally, activate /swapfile swap space immediately, enter:
[[email protected] ~]# swapon /swapfile
Now you can check if the swap works by following command:
[[email protected] ~]# free -m total used free shared buff/cache available Mem: 986 96 75 0 814 695 Swap: 2047 0 2047
- Update /etc/fstab file. To activate /swapfile after Linux system reboot, add entry to /etc/fstab file. Open this file using a text editor such as vim:
[[email protected] ~]# vim /etc/fstab
Append the following line:
/swapfile1 none swap sw 0 0
Save and close the file. Next time Linux comes up after reboot, it enables the new swap file for you automatically.