Linux Essentials

Linux administration pathAvailable

Build a dependable Linux foundation by inspecting before changing, keeping commands reversible, and verifying results.

Difficulty: Beginner
Time: 180 min
Practice: Create and restore a small backup
Assessment: Knowledge check

Before you start

Who is this for?

For IT learners who want to administer a Linux VM or server safely from the command line.

Prerequisites

Basic computer use
A disposable Linux VM or authorised test system

What you'll be able to do

Navigate and manage files
Use pipes and redirection
Inspect processes and logs
Install packages safely
Reason about permissions
Test networking and SSH

Practical outcome

You can build a small backup script and document its permissions, restoration, and failure behaviour.

1. Linux and distributions

Linux technically refers to the kernel. A distribution combines it with user-space tools, a package system, installers, defaults, and a release policy. Debian/Ubuntu, Fedora/RHEL, openSUSE/SUSE, and Arch differ in package commands and support models. Use a disposable VM for experiments and read a command before running it, especially when it uses sudo, writes files, or acts recursively.

2. How a shell command works

The shell parses arguments, expands variables and wildcards, and starts a builtin or external program. Linux filenames and commands are case-sensitive:

name="Ada Lovelace"
printf 'Hello, %s\n' "$name"
command -v bash
man ls
ls --help

Quotes protect spaces and prevent unintended expansion. A command’s exit status is available in $?; zero conventionally means success.

3. Navigate and inspect the filesystem

The filesystem starts at /. Common paths include /home for user data, /etc for system configuration, /var for changing data and logs, /tmp for temporary files, /usr for installed programs, /dev for devices, and /proc//sys for kernel and device views.

pwd
ls -la
cd /var/log
find . -maxdepth 2 -type f -name '*.log'

Absolute paths start at /; relative paths start in the current directory. Hidden names begin with . but are not automatically protected.

4. Manage files safely

mkdir -p ~/bytepath-lab/input
printf 'sample\n' > ~/bytepath-lab/input/example.txt
cp --preserve=mode ~/bytepath-lab/input/example.txt ~/bytepath-lab/
mv ~/bytepath-lab/example.txt ~/bytepath-lab/archive.txt

Inspect a wildcard before deleting. rm has no automatic recycle bin, and rm -r is irreversible. Prefer a disposable lab and explicit paths.

5. Streams, pipes, and search

Programs have standard input, standard output, and standard error. Redirect and combine small tools:

printf '%s\n' *.txt | sort | tee file-list.txt
grep -R --line-number 'timeout' ~/bytepath-lab
command 2>errors.log

> overwrites, >> appends, and 2> redirects standard error. Use awk, cut, sort, and uniq only after confirming the input format.

6. Archives and backups

An archive groups files; compression reduces size. Inspect before extracting:

tar -czf ~/bytepath-lab/backup.tgz -C ~/bytepath-lab input
tar -tzf ~/bytepath-lab/backup.tgz
tar -xzf ~/bytepath-lab/backup.tgz -C ~/bytepath-lab/restore

A backup is trustworthy only after a restore test and an integrity check. Do not extract an unknown archive into a sensitive directory.

7. Processes, services, and logs

ps aux --sort=-%mem | head
pgrep -a ssh
free -h
df -h
systemctl status ssh
journalctl -u ssh --since '15 minutes ago'

kill sends SIGTERM by default and gives a process a chance to stop cleanly. Use SIGKILL only as a last resort. Service names differ by distribution; inspect before changing them.

8. Packages and updates

Use the distribution’s trusted repositories and understand the change before confirming it:

# Debian/Ubuntu
apt search package-name
sudo apt install package-name
# Fedora/RHEL
dnf search package-name
sudo dnf install package-name

Do not mix repositories casually. Verify package origin, signatures, and update policy for third-party software.

9. Users, groups, and permissions

id
getent passwd "$USER"
groups
ls -l file
chmod 640 file

Normal work should use an unprivileged account. sudo grants elevated rights for a specific command and should be used with a reason. For deeper mode, ACL, and special-bit practice, continue to Linux Permissions.

10. A safe Bash script

#!/usr/bin/env bash
set -euo pipefail

source_dir=${1:?usage: $0 SOURCE_DIR DESTINATION}
destination=${2:?usage: $0 SOURCE_DIR DESTINATION}
mkdir -p "$destination"
tar -czf "$destination/backup-$(date +%F).tgz" -C "$source_dir" .
printf 'Created backup in %s\n' "$destination"

set -euo pipefail makes several classes of mistakes visible, but it is not a substitute for testing. Quote variables, validate inputs, and use a temporary directory for experiments.

11. Networking and SSH

Begin with state, then test one dependency at a time:

ip address
ip route
ss -lntup
getent hosts example.test
curl --verbose https://example.test/

A successful ping, DNS lookup, TCP connection, and HTTP response test different layers. SSH is an encrypted remote shell; connect only to authorised systems:

ssh user@192.0.2.10

Verify the host-key fingerprint through a trusted channel on first connection. Protect private keys with restrictive permissions and never commit them.

Practical project: backup and restore

Create ~/linux-lab/input, archive, and restore.
Add three harmless text files and search them with grep.
Write or adapt a script that creates a dated tar.gz.
Set the archive to 640 and verify owner and group.
List the archive before extracting it.
Restore it and compare contents with diff -r.
Document what happens when the input path does not exist.

What you should be able to do now

You should be able to inspect a Linux system, make a controlled change, verify it, and explain the evidence. Continue with Linux Permissions or use the backup and restore lab.