SD card - root dir almost full(?)

[TomS]

I am ssh'ed into my rPi Meteohub (5.1a). It has a 16 gb SD card. The /data filesystem has 10 gigs free (out of 12), but the root filesystem is at 88% full, it's only 1.6 gb and it is using 1.4, 200 mb free.

There is 225 MB in /var/cache/apt/archives, which is an archive of all the installed sw/libraries.

So questions:

-can I delete these archives? Googling suggest perhaps I can?
-do I even need to or is this build stable (i.e. never changing) such that I don't have to worry about this?

(there is also 257 mb in /usr/lib, but that seems like it shouldn't be touched).

Thoughts?

Thanks,

TomS.