What to Do If a Linux Command Says Command Not Found
It's almost always a missing program install, or a typo.
"Command not found" means the system doesn't recognise that command — almost always for one of these two reasons.
1. The program isn't installed
Many commands belong to programs that don't come installed by default. Look for the corresponding package:
sudo apt install program-name
If you don't know the exact package name, search for the command name alongside your distribution in a search engine — it usually matches or is very similar.
2. A typo
Before installing anything, check you've typed the command exactly right — Linux is case-sensitive, and a single extra space or letter triggers this same message.
Tip: use the Tab key while typing —
it autocompletes commands and file names, avoiding typos and saving
you time at the same time.
3. The program is installed but not in the PATH
In less common cases, the program is installed but in a location
the system doesn't search automatically. You can run it with its full
path while you investigate why it isn't in the PATH, for example:
/opt/program/bin/program.
Frequently asked questions
Why does a command work in a tutorial but not on my system?
It's most likely that the corresponding program isn't installed by default on your distribution — install it with your system's package manager before trying to use it.
Is Linux case-sensitive for commands?
Yes, unlike Windows, Linux is case-sensitive for both commands and file names — a capitalisation mistake can cause this same message.