Fix "bash: command not found"

Understanding the Error

Bash cannot find the command you typed.

Fix 1: Check If Command is Installed

# Try finding it
which command_name
whereis command_name
type command_name

# Search package that provides it
# Ubuntu/Debian: apt-file search command_name
# CentOS/RHEL: yum whatprovides */command_name

Fix 2: Install Missing Package

# Common missing commands
sudo apt install curl
sudo apt install wget
sudo apt install git
sudo apt install vim
sudo apt install htop
sudo apt install net-tools   # ifconfig, netstat
sudo apt install iputils-ping  # ping

Fix 3: Fix PATH Variable

# Check current PATH
echo $PATH

# Add common directories
export PATH=$PATH:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

# Make permanent
echo 'export PATH=$PATH:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin' >> ~/.bashrc
source ~/.bashrc

Fix 4: Use Full Path

# Instead of "command", use:
/usr/bin/command
/usr/local/bin/command

Fix 5: Alias Existing Command

# In ~/.bashrc
alias python=python3
alias ll='ls -la'

Fix 6: Check for Typo

# Common typos
grep → gerp
ls → sl
mkdir → md