How to move /tmp to mSATA SSD?

Hi, I’m still struggling with my 1 GB RAM Omnia. Usually during updates, the memory is not sufficient. Now I figured out that although I’ve moved my whole system to SSD, /tmp still uses tmpfs. That might be the reason why updates are so memory-hungry… I quickly looked into /etc/fstab, but there is nothing there. Does anyone have an idea how to move /tmp to the SSD? Also, is there some explicit command/script I need to add to clear the contents of /tmp on boot?

Maybe relevant: Move /var to msata partition (without an answer, though…).

Normally mount should work since it is Linux system.

I’m looking for an automated solution after startup. I fear that exchanging the mount point of /tmp on a running router could end up not very well…

I don’t mean change mount point on a running router.
I mean if mount is done at boot time then it should work, but need to find which script during boot mounts tmp as tmpfs, it seems OpewWrt not doing by standart fstab file or maybe just editing fstab will work(btw mounting again another point should normally shadow it).

I found this: https://github.com/stephank/openwrt/blob/master/package/base-files/files/lib/preinit/10_essential_fs . However, it doesn’t seem like it could be configured in any way, and moreover it is in a 12 years old OpenWRT fork…

Seems script file is
/lib/functions/preinit.sh

I don’t think so. It only mounts some /tmp/root folder…

Guessing these functions, need to study script more

pivot() { # <new_root> <old_root>
	/bin/mount -o noatime,move /proc $1/proc && \
	pivot_root $1 $1$2 && {
		/bin/mount -o noatime,move $2/dev /dev
		/bin/mount -o noatime,move $2/tmp /tmp
		/bin/mount -o noatime,move $2/sys /sys 2>&-
		/bin/mount -o noatime,move $2/overlay /overlay 2>&-
		return 0
	}
}

fopivot() { # <rw_root> <work_dir> <ro_root> <dupe?>
	/bin/mount -o noatime,lowerdir=/,upperdir=$1,workdir=$2 -t overlay "overlayfs:$1" /mnt
	pivot /mnt $3
}

Edit:
Regarding script above it is still mystery how was set old root.

Don’t understand why OpenWrt makes it so complicated. In standart linux tmp is not tmpfs and simply can be mounted to any point by editin’ fstab.