GNURoot is amazing --- it's a non-root chroot which uses ptrace to fake being in a multiuser root environment while being in a single, normal user --- but it doesn't always work. Something about the security systems of modern Androids can cause it to fail in a variety of ways.

Weirdly, the exact failure mode seems to vary from device to device, so one person's tablet will work fine, while another's will report incorrect errnos on any system call which refers to a nonexistent file, while another will fail to load binaries, etc.

I used GNURoot heavily on a Nexus 7 for a while. Worked beautifully. I used it to write on, with a USB keyboard and a word processor what I wrote myself (<plug> http://cowlark.com/wordgrinder </plug>). But then I unwisely upgraded it to Android 5.1 and everything stopped working. These days I use a Chromebook with Crouton.