In Part 1 you learned to find your way around: open a shell, walk the filesystem, move with cd, and read files with cat, less, and man. That is navigation. This lesson turns the shell into a working tool — the three skills that make the command line genuinely powerful for security work.
Prerequisites: linux-basics-part1 for shell navigation and file inspection. This lesson prepares you for linux-command-line-fundamentals, bash-scripting-primer, and later tool lessons that expect you to filter command output.
In this lesson you will:
- Understand the Linux permission model — read / write / execute bits for the owner, the group, and other — how to read them in
ls -l, and how to change them with **chmod** (symbolic like+x, or numeric like755) and ownership with **chown**. - Learn what **
sudois and why working as an ordinary user and only elevating when needed is the principle of least privilege**. - Install software cleanly with the **
apt** package manager (update,install,search,remove) and see why a package manager beats downloading random binaries. - Master the pipe (
|) and redirection (>,>>), the glue that joins small commands together. - Meet the text-processing toolchain — **
grep,cut,sort,uniq,wc,sed,awk** — and build a one-line pipeline that counts and ranks lines, the exact idiom the applied lessons reuse.
As in Part 1, everything you do is local to your own machine — changing permissions on your own files and filtering text you are allowed to read. That same care about authorization applies the moment you point any tool at a system you do not own; see hacking-ethics-and-authorization.
Estimated time: twelve to fifteen minutes.
When you are ready, send the Continue signal.