clear, exit, reboot and what a reload means in TempMV

Three small commands close out the module, and they are a good excuse to be precise about what this machine is. clear wipes the screen. exit ends the shell. reboot restarts the computer. On the practice VM, each of these does slightly less — or slightly more — than you might expect.

clear

clear erases everything on the terminal and puts the prompt at the top. Nothing else changes: files, history and your working directory are untouched. It is purely cosmetic, and it is the right move whenever a wall of output makes you lose your place. Ctrl-L does the same without leaving the line you were typing.

exit

exit ends the current shell. On a desktop, that closes the terminal window; over a remote connection, it logs you out. On this machine the shell on the console is started by init, the first process, with the instruction to respawn it — so when you exit, a fresh shell appears a moment later with a new prompt. You cannot really leave, and nothing is lost by trying. Ctrl-D on an empty line is the same as exit: it sends "end of input", and a shell with no more input to read quits.

~% cd /tmp
tmp% exit

~% pwd
/root

Notice the prompt after the respawn: back to ~%. The new shell starts from scratch — home directory, empty history in memory, default settings. Anything you had set up in the old shell (lesson 69 will introduce variables and aliases) is gone. Files on disk are not affected.

reboot and poweroff

reboot asks init to shut everything down cleanly and start the kernel again; poweroff does the same and then stops. On a real server, files written to disk survive a reboot — that is what disks are for — and only running programs and unsaved work are lost. On a laptop you would be asked for a password first. Here, as root, both commands run immediately, and the next section explains why their effect is bigger than usual.

What this machine really is

The Linux Lab is a complete PC emulated inside your browser tab. The whole operating system — kernel, BusyBox, every directory you have seen — is loaded from a 7 MB image into memory when the page opens. There is no disk. The root filesystem is a RAM disk: writes go to memory and nowhere else. Consequences, stated plainly:

• reboot and poweroff discard every file you created. The machine comes back exactly as the image was built.
• Reloading the page, closing the tab, or navigating away does the same, with no warning and no undo.
• Your course progress — completed lessons, quiz scores, passed tasks — is stored by the website in your browser, not in the VM. It survives reloads.
• Every practice task stages its own files under /root/lab when you open it, so a fresh machine is never a problem: open the task, and the scenario is rebuilt.

That closes the first module. You can read a prompt, find out where you are, look around, move, ask any command for help, and type quickly. Module 2 turns to the verbs: making, copying, moving and deleting the things you have so far only looked at.