Linux swap file

一般 linux 的 swap 都是割一塊分割區
其實也可以 swap file 的方式

如: 造一個 500MB 的 swap file in /tmp/swapfile
dd bs=1048576 count=500 if=/dev/zero of=/tmp/swapfile
mkswap /tmp/swapfile
swapon /tmp/swapfile

進一步加到 /etc/fstab
/tmp/swapfile swap swap defaults 0 0

ref. man mkswap

To setup a swap file, it is necessary to create that file before ini-
tializing it with mkswap , e.g. using a command like

# dd if=/dev/zero of=swapfile bs=1024 count=65536

Note that a swap file must not contain any holes (so, using cp(1) to
create the file is not acceptable).