VI Editor Basics in Linux

Overview and context

In the DevOps and cloud world, you’ll work with Linux servers, often accessed remotely via a terminal, and you’ll modify content in many files, most of which are configuration files.
Using simple redirection with cat is basic and has limited features; it is not suitable for adding or manipulating large amounts of text or for writing code.
Mastering a console-based editor like VI is highly valuable for quickly editing files on remote servers.

There are several text editors available in Linux, such as VI, VIM, Nano, etc.
This course focuses on VI editor, which happens to be the most popular one.
VI editor comes installed by default with most operating systems.
To open a file, run the VI command and specify the filename: vi <filename>. The terminal opens the file and you are now inside the VI editor.

VI has two modes of operation: command mode and insert mode.
When you open a file in VI editor, you are by default in the command mode.
In command mode, you can issue commands to the editor (copy/paste lines, delete a line or a word, navigate between lines, etc.), but you cannot write contents to the file.
To write contents to the file, you must switch to the insert mode.
To switch to the insert mode, type lowercase i.
Once you are in insert mode, you may modify the file contents as you would normally.
To switch back from insert mode to the command mode, press the Escape key.

Move around the editor using the arrow keys or the keys k, j, h, l on your keyboard:
- K to go up
- h to left
- j to down
- l to the right
To delete a character, press x.
Typing dd deletes the entire line.
To copy a line, type yy.
To paste it, type p.
To scroll the page up or down, press Ctrl+u or Ctrl+d.

Typing colon (:) takes you to the command prompt where you can type commands.
Save the changes made to the file and write the file to disk: :w. You can optionally specify a file name as well, e.g., :w newname.txt.
Discard any unsaved changes and quit VI: :q.
Save changes and quit: :wq (or :x, which is similar in practice).

To find a word, e.g., the word off, type /off.
All occurrences of the word are highlighted, and the cursor is positioned at the first occurrence.
To move to the next occurrence, press n.
You can continue to press the n key to move to subsequent occurrences.

Default mode is command mode; to edit text, switch to insert mode with i and return to command mode with Esc.
These capabilities are essential when editing files on remote Linux servers via SSH.
Practical considerations:
- Be mindful of file permissions and ownership when editing system or configuration files.
- It’s prudent to make a backup before making large changes.
- Practice in non-critical files to gain familiarity with the commands.
Quick hypothetical workflow:
- Open a config file with vi /etc/example.conf.
- Search for a parameter with /parameter and navigate with n to the relevant line.
- Enter insert mode with i to modify the value.
- Save with :w and exit with :q once changes are validated.

VI’s two-mode design separates navigation/editing actions, reducing accidental edits and enabling efficient editing, which is crucial when working across many files on remote servers.
In practice, knowing how to quickly search, copy/paste lines, and manage simple edits can save significant time during system administration and DevOps tasks.

Open: vi <filename> — default mode is command mode.
Edit: switch to insert mode with i; return with Esc.
Move: use arrow keys or k (up), j (down), h (left), l (right); note the transcription uses K for up.
Edit commands: x (delete char), dd (delete line), yy (copy line), p (paste).
Scroll: Ctrl+u (up), Ctrl+d (down).
Save/quit: :w, :q, :wq (optionally with a filename for :w).
Search: /word; navigate with n.
Final takeaway: VI is a foundational tool for efficient remote editing, with practical implications for reliability, speed, and consistency in DevOps workflows.