chmod Question

Say u use chmod -R while logged in as root and remove the execute permission
from all commands. How could this be fixed?

i start playing unix 1979
no internet, no forums, no chance to get help or teachers
the only way: READ man pages, try it!
man chmod, that's what you need.
you could try: chmod -R a-x .
don't forget: directories need the 'x' permissions!
so it's a little complicated:
find . -type f|xargs chmod 555
or a shell-script.

Yeah, well, I know that the man is supposed to be my best friend
I recently started learning UNIX System Administration and am worried that
I might acidentally mess up something, so I wanna know if something I could
mess up could be fixed and how.
That's why I posted this question.
Tnx for your help.

I hate to rain on your parade here, but about the only way to recover from something like that is to reload the OS, rebuild the filesystems, and reload the files from backup tapes. You need good backups to recover from disasters. This would be a disaster, so treat it that way.

Use the chmod command? How? It has no execute permission. Run a shell script? With what as an interpreter? The shells have no execute permission. Basicly, this box is not going to even be bootable. Being completely unable to run commands at all is simply a very big problem.

There are other approaches... You could try to boot from an install cd or something. But rebuilding a box from scratch is a skill you need. You should be good at it. And you should have current backups you trust. With most systems, I can install the os and start spinning backups tapes in less than 2 hours. The tapes will take time to read...how long depends on how much data. If you try to recover from this by booting an install cd, it will take longer than that just to get the box bootable. You will be mopping up the mess for days. And in the end you will probably wind up reinstalling anyway.

So with a disaster of this magnitude, my advice is to simply re-install.

Yep, I figured it would be the simplest thing, but just wanted to make sure if there were some other options. As I said before, I just wanna make sure I can fix things I might mess up.