archlinux live archiso expand cow persistent overlay

Seems that by default, archiso cow persistent space is set to 262M. Too short for some needs [1]. Linux said the cow fs was filled while installing some packages. Struggle to find a way to add some more writeable space. Then I saw in mtab fs options that cowspace being tmpfs, has a size parameter. So remounting it with different settings.

sudo mount -oremount,size=<space>k cowspace

did the job

now there's an overlay named airootfs, it will show the old size, remounting put it in sync.

sudo mount -oremount airootfs

now both will show <space>.