How can I make a shell to show up in my own distro (linux)? [closed]

Question

I am interested in Linux and been digging it for a while. I just learnt to compile a Linux kernel from source and boot it with Grub which lands you with the shell of the kernel.

Now as soon as the kernel is loaded into memory it searches for the init to load it. My agenda is to bring up a shell (which a normal user can use - like bash).

So, How can I bring it in?

Do I need to configure init to load the bash shell or is there something I could do?

I am building my own distro and I just need the distro to have a shell (bash) and nothing else.

Answer 1

Hmm. This should not be complicated to achieve, but it's also very complex :)

You can simply do what Alexander suggested (init=/bin/bash), and you'll do fine.

The init process is what the kernel calls, and it kicks off all of your userland. Login terminal included. If your init just spawns that bash terminal, you're fine. But if that terminal crashes, or exits, init is supposed to clean up. If some of the processes you launch from terminal die, you need to clean up. If they die, then their children need a new parrent process, it'll be your init.

I highly recommend dedicating 10 minutes to read this, it's very friendly overview of what init does:

http://tilde.town/~elly/userland.txt

Then you'll get closer to understand what it entails to run your own init.

A relevant part of that link says:

There is only one thing we need to do: provide an initial binary to launch at any of these paths: /sbin/init, /etc/init, /bin/init, or /bin/sh. This process (init) is run as pid 1.

The init process needs to do two things:

• Never exit (if init exits, the kernel panics)

• Reap zombie processes

The rest of the text then implements a simple init.

Answer 2

"terminal" (a physical computer) and "bash" (a shell) are completely different. I'm not entirely sure what you are asking, but you can add init=/bin/bash to the kernel command line in order to boot straight into bash.

Answer 3

bash isn't a terminal, is a shell.

The init process, once the boot process has finished and if the machine is running in a text-only runlevel (so without X Windows), calls eventually getty which in turn calls login. That's the process responsible for presenting the login prompt and allowing users to log in. This is what happens in all Linux distros.

What you want to do is simply to define bash as the default login shell for users (assuming you want a multi-user environment).