While Kobo does use a Linux kernel, it does not include a full Linux environment. For instance the shell and many of the standard executables are implemented using busybox
https://busybox.net/
Kobo only includes binaries / commands for what they need.
Additionally the Kobo Wifi is a very VERY old device using (in your case) f/w 1.9 from 2011. I'd normally suggest checking pgaskin's list of firmwares for an upgrade but I think you're SOL
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