// eknathalabs.com · linux lab

Master Linux.
Admin with Confidence.

A structured, hands-on Linux learning lab — LFCS exam domains, AI-powered tools, 250+ commands, 100-question quiz, and full lab walkthroughs. Built by a Platform Engineer, for Platform Engineers.

▶ Start Learning ⌨ Cheatsheet ✦ Take Quiz ⚗ Practice Labs
eknatha@linuxlab ~ bash
eknatha@linuxlab $ systemctl status nginx
● nginx.service - A high performance web server Loaded: loaded (/lib/systemd/system/nginx.service) Active: failed (Result: exit-code) Process: 1234 ExecStart=/usr/sbin/nginx (code=exited) eknatha@linuxlab $ journalctl -u nginx -n 20
Aug 12 09:42:11 nginx[1234]: bind() to 0.0.0.0:80 failed Aug 12 09:42:11 nginx[1234]: (98: Address already in use) eknatha@linuxlab $ ss -tlnp | grep :80
LISTEN 0 128 0.0.0.0:80 users:(("apache2",pid=999)) # Port 80 held by apache2 — stop it first
eknatha@linuxlab $ sudo systemctl stop apache2 && sudo systemctl start nginx
✓ nginx.service started — Active: active (running) eknatha@linuxlab $
14
Modules
8
AI Tools
250+
Commands
100
Quiz Q&A
14
Labs
LFCS
Exam Ready
70+
Error Codes

// LFCS Exam Blueprint

Official Domain Coverage

Every module, quiz question, and lab maps to an official LFCS domain. 2-hour performance-based exam · 17–20 tasks · 67% passing score.

25%
Operations & Deployment
systemd, boot process, cron, package management, containers
25%
Networking
interfaces, routing, iptables, firewalld, SSH, DNS, NFS
20%
Storage
LVM, partitioning, filesystems, RAID, mounting, swap
20%
Essential Commands
find, grep, sed, awk, pipes, redirects, permissions, archives
10%
Users & Groups
useradd, sudo, PAM, passwd, groups, LDAP basics

// Learning Path

Structured Modules

14 modules from essential commands to advanced security. Click any module to deep dive.

⌨️
Beginner
Essential Commands
Navigation, file ops, find, grep, text manipulation, pipes, redirects, stdin/stdout/stderr.
findgrepsed/awkLFCS 20%
🔐
Beginner
Users, Groups & Permissions
useradd, passwd, sudo, ACLs, chmod, chown, sticky bit, SUID/SGID, umask.
useraddsudoACLLFCS 10%
⚙️
Beginner
systemd & Service Management
systemctl, journalctl, unit files, targets, boot sequence, service dependencies.
systemctljournalctlLFCS 25%
💾
Intermediate
Storage & Filesystems
Partitioning (fdisk/gdisk), mkfs, mount, fstab, swap, ext4/xfs/btrfs.
fdisklvmmountLFCS 20%
🗄️
Intermediate
LVM — Logical Volume Manager
pvcreate, vgcreate, lvcreate, resize, snapshots, thin provisioning.
pvcreatelvcreatelvextend
🌐
Intermediate
Networking Fundamentals
ip, nmcli, netplan, static IPs, routes, DNS resolution, ss, netstat, troubleshooting.
ip addrnmclissLFCS 25%
🛡️
Intermediate
Firewall — iptables & firewalld
iptables chains, rules, NAT, PREROUTING, firewalld zones, rich rules, persistence.
iptablesfirewalldnft
🔑
Intermediate
SSH & Remote Access
Key-based auth, sshd_config hardening, port forwarding, jump hosts, scp/rsync.
ssh-keygensshdrsync
📦
Intermediate
Package Management
apt/dpkg (Debian), dnf/rpm (RHEL), snap, flatpak, compiling from source.
aptdnfrpm
📊
Intermediate
Process & Resource Management
ps, top, htop, kill, nice/renice, ulimit, cgroups, load average, memory analysis.
pstopcgroups
🕐
Intermediate
Cron & Task Scheduling
crontab syntax, system cron, at, anacron, systemd timers — all approaches covered.
crontabatsystemd timer
📋
Advanced
Shell Scripting for Sysadmins
Bash scripting patterns, error handling, loops, functions, heredocs, real automation scripts.
bashscriptingautomation
🐳
Advanced
Containers & Docker Basics
docker run/build/compose, image management, networking, volumes — the LFCS container domain.
dockercontainersLFCS
🔒
Advanced
SELinux & AppArmor
Mandatory access control, contexts, booleans, audit logs, troubleshooting denials.
SELinuxAppArmorMAC

// Interactive AI Tools

Built-in Linux Tools ✦ AI Powered

Paste errors, describe tasks, generate configs — without leaving the page.

🔴
✦ AI
Error Explainer
Paste any Linux error or kernel panic. Get root cause, fix commands, and how to prevent it.
⚙️
✦ AI
systemd Unit Generator
Describe a service in plain English → get a production-ready .service unit file with explanations.
📋
✦ AI
Bash Script Explainer
Paste any shell script. Get a line-by-line breakdown, potential bugs, and safer alternatives.
🌐
✦ AI
Network Troubleshooter
Describe your networking issue. Get a step-by-step debug checklist with exact commands to run.
🛡️
✦ AI
iptables Rule Builder
Describe your firewall requirements → get working iptables/nftables rules with explanations.
💾
✦ AI
LVM Planner
Describe your storage layout → get full LVM commands: pvcreate, vgcreate, lvcreate, resize.
🔐
✦ AI
Permission Debugger
Paste a "Permission denied" error + context. Get the exact chmod/chown/ACL fix needed.
🕐
✦ AI
Cron Expression Builder
Describe your schedule in English → crontab expression. Paste expressions to get explanations.

// Quick Reference

Linux Cheatsheet

250+ commands — searchable, click any command to copy. LFCS exam shortcuts included.

250+ commands
find / -perm /4000Find all SUID files on system⎘ copy
journalctl -u nginx --since "1 hour ago"View nginx logs from last hour⎘ copy
ss -tlnpList all TCP listening ports with process⎘ copy
lvcreate -L 10G -n data vg0Create 10G LVM logical volume⎘ copy
iptables -L -n -v --line-numbersList all iptables rules with line numbers⎘ copy
grep -r "pattern" /etc/ --include="*.conf"Recursive grep in .conf files only⎘ copy
tar -czf backup.tar.gz /var/dataCreate compressed tar archive⎘ copy
rsync -avz --delete src/ user@host:/dst/Sync with delete of removed files⎘ copy
nmcli con mod eth0 ipv4.method manual ipv4.addresses 192.168.1.10/24Set static IP via NetworkManager⎘ copy
ausearch -m avc -ts recentFind recent SELinux denials⎘ copy

// Practice Questions

LFCS Quiz — 100 Questions

Scenario-based questions mapped to official LFCS domains. Filter by domain and difficulty. Track your score.

Networking · 25% Medium
You need to configure a persistent static IP of 10.0.0.5/24 on interface eth0 on an Ubuntu system using NetworkManager. Which command achieves this AND survives a reboot?
Aip addr add 10.0.0.5/24 dev eth0
Bnmcli con mod eth0 ipv4.method manual ipv4.addresses 10.0.0.5/24 && nmcli con up eth0
Cifconfig eth0 10.0.0.5 netmask 255.255.255.0
Decho "10.0.0.5/24" > /etc/network/eth0.conf && systemctl restart networking

// Hands-on Scenarios

Practice Labs

14 full step-by-step labs modelled on production incidents and LFCS exam tasks.

01
Recover a Broken Boot — GRUB Rescue
Simulate and recover from a corrupted GRUB config. Single-user mode, chroot, reinstall bootloader.
~45 minIntermediate
02
LVM Full Disk — Expand Without Downtime
Simulate a 100% disk usage alert. Add a PV, extend VG, resize LV, grow filesystem live.
~30 minIntermediate
03
Nginx Fails to Start — Port Conflict Debug
Diagnose port conflict with ss/fuser, stop conflicting service, configure nginx, persist with systemd.
~20 minBeginner
04
Set Up SSH Hardening — No-Password Auth
Key-based auth only, disable root login, change default port, configure fail2ban, test lockout.
~35 minIntermediate
05
Firewall: Isolate a Compromised Web Server
Use iptables to allow only port 443 inbound, block all outbound except DNS, persist rules.
~40 minAdvanced
06
SELinux Denial — Fix Without Disabling
App fails due to SELinux AVC denial. Use audit2allow, setsebool, restorecon — never setenforce 0.
~45 minAdvanced

// Error Encyclopedia

Linux Error Code Encyclopedia

70+ Linux errors — root cause, fix commands, and prevention. Searchable. Click any to expand.

Job for nginx.service failed because the control process exited with error code systemd
bind() to 0.0.0.0:80 failed (98: Address already in use) Network
GRUB error: unknown filesystem. Entering rescue mode... Boot
No space left on device (ENOSPC) Storage
type=AVC msg=audit: denied { read } for path=... comm="nginx" Permissions
ssh: connect to host 192.168.1.1 port 22: Connection refused Network
sudo: user not in the sudoers file. This incident will be reported. Permissions
E: Could not get lock /var/lib/dpkg/lock — open (11: Resource temporarily unavailable) Package