Linux 'command not found': Install the Package or Fix PATH

Debian / Ubuntu — apt

1. sudo apt update
2. sudo apt install [command-name]
3. [command-name] --version

RHEL / CentOS / Fedora — dnf

1. sudo dnf install [command-name]
2. [command-name] --version

Fix PATH — add directory permanently

1. which [command]
2. echo 'export PATH="$PATH:/path/to/directory"' >> ~/.bashrc
3. source ~/.bashrc
4. [command-name] --version

• If which [command] returns a path but shell still says not found → Open a new terminal — the PATH change may not have been loaded in the current session
• If Command works as root but not as your user → The binary is in /sbin or /usr/sbin which is in root's PATH but not the user PATH. Add /usr/sbin to your PATH.
• If Command exists on another machine but not this one → Check the distro-specific package name: apt-cache search [keyword] or dnf search [keyword]

• snap/flatpak installs use different paths not in default PATH — check with 'snap list' or 'flatpak list' if the command was installed that way
• Python on Ubuntu 20.04+: 'python' is not installed by default, only 'python3'. Install the alias: sudo apt install python-is-python3
• Scripts with #!/usr/bin/env python shebang will fail if only python3 is installed. Update the shebang line to #!/usr/bin/env python3

# Step 1: check if the binary exists anywhere
which [command]
find /usr /usr/local /opt -name "[command]" 2>/dev/null

# Step 2: install it (Ubuntu/Debian)
sudo apt update && sudo apt install [command]

# Step 3: if found but PATH is wrong
echo 'export PATH="$PATH:/path/to/bin"' >> ~/.bashrc
source ~/.bashrc

# Step 4: verify
which [command]
[command] --version