Are there cases where vi is the only option?

Inside the Ubuntu ecosystem, I do not think this case can even exist, as vi would at least be a vim-tiny, which is already a “real vim” far from “real vi.”

In the context of resource limited embedded systems, which are not normally Ubuntu, you may just have a vi that turns out to be a link to busybox. And not space left. Then, vi is the only option.

Apart from that, I think situations where vi the only option are not very common at all today, even outside the Linux world.

But there can easily be situations where vi is the only option you can plan for, the only option that certaily will exist in some future situation — which will happen inside a customer’s over-chilled server room, most probably.

Imagine you are called by a customer:

Customer: I need to get this configuration fixed! Now!! I don’t know how, but I can tell you where the configuration file is. Can you help me!?!

You: Ok, what kind of system is that running on?

Customer: Oh, it's on server foo, ahh... it's running... can't remember, something with "ix" in the end, or mayeb with "ux"...

No problem, by now, you know there will be vi!

Vi is never the only option; you can always use ed instead.

Well, there is one case where you need the vi editor, lets assume:

• there is not graphical interface
• you're on some strange unknown *nix system
• your terminal look like this:

• you have enough of guys like this:

As you can see there is no numerical keypad. With the old vi (and I mean the original traditional vi, not vim, vim.tiny, or vim.basic) you can edit a file with this keyboard. Without arrow keys? Yes, when you're in command mode you moved through the file with h, j, k and l, like a pro. h was left, j was down, k was up and l was right.