One of my CentOS 7 Core hosts on CloudCone has only 256MB of memory. Here's my note while enable swap partition for it.
[tuyendq@1 ~]$ free
total used free shared buff/cache available
Mem: 237244 76768 44640 12780 115836 127416
Swap: 0 0 0
[tuyendq@1 ~]$
[tuyendq@1 ~]$ sudo dd if=/dev/zero of=/swap count=2049 bs=1MiB [sudo] password for tuyendq: 2049+0 records in 2049+0 records out 2148532224 bytes (2.1 GB) copied, 14.3186 s, 150 MB/s [tuyendq@1 ~]$
[tuyendq@1 ~]$ sudo chmod 600 /swap
[tuyendq@1 ~]$ which mkswap /usr/sbin/mkswap [tuyendq@1 ~]$ sudo mkswap /swap Setting up swapspace version 1, size = 2098172 KiB no label, UUID=0cea54e6-42d4-49c9-8f9b-f30e62582acf [tuyendq@1 ~]$
[tuyendq@1 ~]$ sudo swapon /swap
[tuyendq@1 ~]$ free
total used free shared buff/cache available
Mem: 237244 78120 7140 12780 151984 126116
Swap: 2098172 0 2098172
[tuyendq@1 ~]$
[tuyendq@1 ~]$ cat /etc/fstab # # /etc/fstab # Created by anaconda on Mon Jul 14 18:58:05 2014 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/vda1 / ext4 defaults 1 1 #/dev/vda2 swap swap defaults 0 0 [tuyendq@1 ~]$
[tuyendq@1 ~]$ echo "/swap swap swap defaults 0 0" | sudo tee -a /etc/fstab /swap swap swap defaults 0 0 [tuyendq@1 ~]$ cat /etc/fstab # # /etc/fstab # Created by anaconda on Mon Jul 14 18:58:05 2014 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/vda1 / ext4 defaults 1 1 #/dev/vda2 swap swap defaults 0 0 /swap swap swap defaults 0 0 [tuyendq@1 ~]$