mkninitcpio-unsquashtmpfs decompresses a root directory, squashfs image and mounts it to a tmpfs filesystem (i.e. memory). Its motivation is for use on an install disk. These kernel parameters are necessary (device name can be: kernel name, LABEL, or UUID):

    root=/new_root
    squashimgpath=[/device/...]:[/path/to/file.squashfs]
    squashtmpsize=[number of bytes]

HOOKS="... block unsquashtmpfs filesystems ...