Master Essential Linux Commands: wget, scp, ssh-keygen, chmod, tar

The article assumes readers have basic command‑line experience and presents six useful Linux commands with practical tips, aiming to deepen command‑line proficiency.

wget

The wget utility downloads files over HTTP, HTTPS, or FTP and is included in most Linux distributions. The simplest usage is to provide the URL of the target file.

wget http://website.com/static/images/header.jpg

wget

runs non‑interactively, allowing it to continue downloading after the user logs out.

scp

scp

(secure copy) transfers files between a local machine and a remote host over SSH. It works like cp but with a remote source or destination.

Download a file from a remote server:

scp [email protected]:/path/to/foobar.txt /some/local/directory

Upload a file to a remote server:

scp /some/local/directory/foobar.txt [email protected]:/destination/path/

Use the -r option to copy directories recursively.

ssh-keygen

The ssh-keygen command creates a new SSH key pair, which can be added to services like GitLab or Bitbucket to enable password‑less authentication. ssh-keygen -t ed25519 The example uses the modern Ed25519 algorithm; users should research other available algorithms as needed.

chmod

chmod

changes file system object permissions on Unix‑like systems. Correct permission settings are crucial for security and functionality.

Example granting read/write to the owner and group for robots.txt: chmod 664 robots.txt Example granting read, write, and execute to the owner and group for a directory public/images while giving others read and execute access:

chmod 775 public/images

tar

The tar command creates and extracts archive files. It is the most common tool for bundling multiple files into a single archive.

Create an archive of a directory: tar -cvf my-archive.tar /path/to/directory Extract the archive to a specific location:

tar -xvf my-archive.tar -C /home/myfolder/

alias

Aliases let you define short shortcuts for long commands. A temporary alias works only for the current shell session.

alias short-command="your custom and very long command here"

To make an alias persistent, add it to the user’s shell configuration file (e.g., ~/.bashrc or ~/.zshrc).

Output Redirection & Command Chaining

Redirect command output to a file using >: ls -al > myfile Run multiple commands sequentially with a semicolon ( ;), regardless of success: ls -al; pwd; Execute the second command only if the first succeeds using &&: mkdir images && cd images Execute the second command only if the first fails using || (example omitted for brevity).