Dphys-swapfile setup fails

$ sudo /sbin/dphys-swapfile setup
[sudo] password for drew:
computing size, drew@odroid:~$ sudo /sbin/dphys-swapfile swapon
/sbin/dphys-swapfile: ERROR: swap file /var/swap missing! you need to first run /sbin/dphys-swapfile setup to generate one
$

$ cat /etc/dphys-swapfile

/etc/dphys-swapfile - user settings for dphys-swapfile package

author Neil Franklin, last modification 2010.05.05

copyright ETH Zuerich Physics Departement

use under either modified/non-advertising BSD or GPL license

this file is sourced with . so full normal sh syntax applies

the default settings are added as commented out CONF_= lines

where we want the swapfile to be, this is the default

#CONF_SWAPFILE=/var/swap

set size to absolute value, leaving empty (default) then uses computed value

you most likely don’t want this, unless you have an special disk situation

#CONF_SWAPSIZE=

set size to computed value, this times RAM size, dynamically adapts,

guarantees that there is enough swap without wasting disk space on excess

#CONF_SWAPFACTOR=2

restrict size (computed and absolute!) to maximally this limit

can be set to empty for no limit, but beware of filled partitions!

this is/was a (outdated?) 32bit kernel limit (in MBytes), do not overrun it

but is also sensible on 64bit to prevent filling /var or even / partition

#CONF_MAXSWAP=2048

D’Oh!

It’s Ubuntu Mate 18.04.1

fallocate --length 2GiB /var/swap
mkswap /var/swap

Or, something similar did not get executed.

Arghh! At the moment, I’m think odroid.com broke it when the implemented support for their board.

But, I could be barking up the wrong tree.