adb-shell : /sbin/sh: command: not found I've managed to root Google Nexus 7 (2013 Wi-Fi) and now I have CyanogenMod 10.2-20130919-NIGHTY-grouper running on it and Clockworkmod recovery v6.0.1.9 following this guide.

Then I downloaded and installed Thinktube image-file to allow ad-hoc networking. 

I am now able to create ad-hoc network in my tablet (not yet tested with other same-model tablets) and I can see the adhoc network from other iOS phones and adnroid 2.1 only. However, I want to make sure that:

does Thinktube image-file actually support OLSR rooting protocol or not ?

if not, then I am already following this guide to download, install and enable OLSR mode. 

But, when I am in the Recovery-mode in my tablet, and when i open the adb-shell from my PC, I can list files and browse folders in my tablet normally. But I cannot run any other command on the adb-shell. it always gives me this error:

/sbin/sh: "any-command-rather-than-ls-&amp;-cd": not found


what is this error ?  what did I do wrong ? and what I should do to fix it?
Unlike a desktop GNU/Linux system, Android isn't designed for command-line use, so it doesn't come with the full set of command-line programs that a GNU system would have. It only has the most basic commands (like the ones you've already seen working), and Android-specific utilities such as am, pm, bmgr.

You can get access to the basic POSIX commands (such as less and grep) by installing Busybox. There are several installers for it on Google Play. For any more specialist programs like make, you'll need to find an Android port of the particular program and install it.