Day 1 - Shell from zero
This is Day 1 of DevOps Engineer Mastery. Today is not Kubernetes. Today is: can you say what actually ran, where you are, and whether it succeeded.
What today is for
- Honest scores in Your Starting Assessment (above). Chat is not a 5.
- Install or confirm a toolchain you can actually use (terminal, Git, editor). Do not dump company PATH or tokens into a public place.
- Write the no-AI rule in that same assessment: on write days, your first version is yours. AI may review later. AI does not author the first file.
- Interview line: what you have operated versus what you have authored.
Words
Terminal is a window. Shell is the program that reads commands. Command is a name plus arguments. A program sits on disk; a process is that program while it is running (Day 5).
pwd answers "where am I?" That directory is the current working directory. /abs is absolute. rel is relative to here.
ls answers "which names are here?" File vs directory is a real distinction. You will need it on Day 4.
PATH is a search list. command -v foo answers "which file runs when I type foo?"
stdin / stdout / stderr:
>replaces a file>>appends2>is stderr<reads stdin from a file|pipes stdout of one command into stdin of the next
$? is the last exit code. 0 means success by convention, not because Bash is magic.
Quoting:
- unquoted - the shell splits and expands
'exact'- literal"$VAR"- the value of VAR, still one word if you keep the quotes
Glob: * ? [ab].
NAME=x exists in this shell. export NAME=x is visible to children. Check with env and printenv.
Practise
- Inventory:
pwd,ls,command -v bash,echo $PATH,echo $?after a command that works and one that does not. - Start a child shell,
exportone variable and do not export another. In the child, print both. Only the exported one should appear. Write down what you saw. - Fill Your Starting Assessment. Do not inflate scores because you have used a cloud portal at work.
- Write the no-AI rule in that assessment. One paragraph. Yours.
Production constraint
No tokens, company PATH dumps, or internal hostnames in anything you publish.
AI review (reject this)
"You know Kubernetes because you have used AKS."
Using a portal is not authorship.
Interview kill
Show a file you wrote with no AI. Then say, out loud, what you have operated versus what you have authored.
Definition of done
Reading this page is not done. The day is done when your starting assessment is saved, the no-AI paragraph is in it, the child-shell export experiment has evidence, and you can explain PATH, $?, and quoting without notes.