LFCS Sample Practice Questions¶

Practice Resources¶

• Linux Journey
• OverTheWire Bandit
• killer.sh LFCS Simulator

Section 1: Essential Commands (25%)¶

Question 1.1¶

Find all files in /var larger than 50MB and list them with their sizes.

find /var -type f -size +50M -exec ls -lh {} \;
# Or
find /var -type f -size +50M -ls

Question 1.2¶

Replace all occurrences of "error" with "warning" in /var/log/app.log without creating a backup.

sed -i 's/error/warning/g' /var/log/app.log

Question 1.3¶

Create a compressed tar archive of /etc named etc-backup.tar.gz.

tar -czvf etc-backup.tar.gz /etc

Question 1.4¶

Set permissions on /data directory so owner has full access, group has read/execute, others have no access. Apply recursively.

chmod -R 750 /data

Section 2: Operation of Running Systems (20%)¶

Question 2.1¶

List all running services and their status.

systemctl list-units --type=service --state=running

Question 2.2¶

Configure the nginx service to start automatically at boot.

systemctl enable nginx

Question 2.3¶

Find the process using the most CPU and kill it.

# Find top CPU process
ps aux --sort=-%cpu | head -2

# Or use top/htop to identify PID, then:
kill -9 <PID>

Question 2.4¶

Schedule a script /opt/backup.sh to run every day at 2:30 AM.

crontab -e
# Add line:
30 2 * * * /opt/backup.sh

Section 3: User and Group Management (10%)¶

Question 3.1¶

Create a user "developer" with home directory /home/developer and shell /bin/bash.

useradd -m -d /home/developer -s /bin/bash developer

Question 3.2¶

Add user "developer" to the "docker" group as a secondary group.

usermod -aG docker developer

Question 3.3¶

Set password expiry for user "developer" to 90 days.

chage -M 90 developer

Section 4: Networking (12%)¶

Question 4.1¶

Display all network interfaces and their IP addresses.

ip addr show
# Or
ip a

Question 4.2¶

Add a static route to network 10.0.0.0/24 via gateway 192.168.1.1.

ip route add 10.0.0.0/24 via 192.168.1.1

Question 4.3¶

Open port 8080/tcp in the firewall permanently.

# firewalld
firewall-cmd --permanent --add-port=8080/tcp
firewall-cmd --reload

# Or iptables
iptables -A INPUT -p tcp --dport 8080 -j ACCEPT

Question 4.4¶

Configure the system to use DNS server 8.8.8.8.

# Edit /etc/resolv.conf
echo "nameserver 8.8.8.8" >> /etc/resolv.conf

# Or for permanent (systemd-resolved)
# Edit /etc/systemd/resolved.conf and add:
# DNS=8.8.8.8

Section 5: Service Configuration (20%)¶

Question 5.1¶

Configure SSH to disable root login.

# Edit /etc/ssh/sshd_config
# Set: PermitRootLogin no

sed -i 's/^#*PermitRootLogin.*/PermitRootLogin no/' /etc/ssh/sshd_config
systemctl restart sshd

Question 5.2¶

Configure NTP to sync time with pool.ntp.org.

# For systemd-timesyncd
# Edit /etc/systemd/timesyncd.conf
# NTP=pool.ntp.org

# Or for chrony
# Edit /etc/chrony/chrony.conf
# server pool.ntp.org iburst

systemctl restart systemd-timesyncd
# Or
systemctl restart chronyd

Question 5.3¶

Set up a basic Apache virtual host for domain example.com serving content from /var/www/example.

# Create /etc/apache2/sites-available/example.com.conf (Ubuntu)
# Or /etc/httpd/conf.d/example.com.conf (RHEL)

cat << EOF > /etc/apache2/sites-available/example.com.conf
<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/example
    <Directory /var/www/example>
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>
EOF

a2ensite example.com.conf
systemctl reload apache2

Section 6: Storage Management (13%)¶

Question 6.1¶

Create a new partition on /dev/sdb using all available space.

fdisk /dev/sdb
# n (new partition)
# p (primary)
# 1 (partition number)
# Enter (default first sector)
# Enter (default last sector)
# w (write)

# Or with parted
parted /dev/sdb mklabel gpt
parted /dev/sdb mkpart primary 0% 100%

Question 6.2¶

Create an ext4 filesystem on /dev/sdb1 and mount it at /data.

mkfs.ext4 /dev/sdb1
mkdir -p /data
mount /dev/sdb1 /data

# For persistent mount, add to /etc/fstab:
echo "/dev/sdb1 /data ext4 defaults 0 2" >> /etc/fstab

Question 6.3¶

Create an LVM logical volume named "data" of 10GB from volume group "vg01".

lvcreate -L 10G -n data vg01

Question 6.4¶

Extend logical volume /dev/vg01/data by 5GB and resize the filesystem.

lvextend -L +5G /dev/vg01/data
resize2fs /dev/vg01/data    # For ext4
# Or
xfs_growfs /dev/vg01/data   # For XFS

Quick Reference Commands¶

# System info
uname -a
hostnamectl
cat /etc/os-release

# Disk usage
df -h
du -sh /path

# Memory
free -h

# Processes
ps aux
top
htop

# Services
systemctl status service
systemctl start/stop/restart service
systemctl enable/disable service

# Logs
journalctl -u service
tail -f /var/log/syslog

# Network
ip addr
ip route
ss -tulpn
netstat -tulpn

Exam Tips¶

1. Know your editor: vim or nano - be fast
2. Use tab completion: Save time and avoid typos
3. Check man pages: man command is your friend
4. Verify your work: Always check if changes took effect
5. Time management: Don't spend too long on one question
6. Read carefully: Understand what's being asked

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