LFCS Tips

Exam tips

• Login into the right machine before attempting to answer the questions
• Read the questions atleast twice
• Understand the copy and paste shortcut between the question pane and the virtual machine as it varies due to OS
• Use apropos, man and info command to get some initial help
• If no help found, use find by searching for a keyword (time consuming)
• If no help found, use locate by searching for a keyword (less time consuming); you may to install it first and use updatedb to update the database
• Look out for typo while naming, configuring, permission string etc.
• Use fg and bg efficiently
• Use ps and jobs to keep track of the running processes
• Use htop instead of top
• Always mark your questions for review
• Always manually navigate to each question using the prev and next buttons
• Switch to sudo whenever is necessary
• Whenever you create a file, make sure the content is properly formatted and the proper permissions have been configured
• Use git log to validate the git commit
• Use git diff to validate the git commit
• Use docker commands to validate the container/image/logs

Sample questions

• Build and install software from source
• Fix apache process to start successfully
• Find the large files recursively and delete the largest one
• Find the files based on the permissions
• Find the high CPU and high read process and kill it
• Git init, commit, and push it to remote
• Docker run command with restart policy, port, and image
• Extend LV
• Create a swap partition and add it to /etc/fstab
• Mount NFS with ro, rw w/ security options
• Create a netfilter to allow port 8080
• Enable ntp and change the timezone
• Change nproc for the user hard and soft limit
• Schedule a cron tab for the user to take a backup
• Configure sshd to allow keyboard authentication for the user
• Create a bash script and run it as a cron job
• Creae a new user and add it to the group e.g. sudo
  • Make the group as primary/secondary
• Create vm swappiness and set it to 10; make it persistent
• Create a xfs filesystem and mount it
• Create a VM using virt-install and autostart it
• Fix the high disk usage by deleting the files and by finding the mount
• Find the correct certificate and private key and delete the others
• Generate the certificate for the new CN

Useful commands

General Linux commands

• man
• info
• locate
• find
• updatedb
• htop
• top
• ps
• jobs
• fg
• bg
• sudo

find commands

• find / -name "file_name" -type f
• find / -name "file_name" -type d
• find / -name "file_name" -type l
• find / -name "file_name" -type s
• find / -name "file_name" -user "username"
• find / -name "file_name" -group "groupname"
• find / -name "file_name" -perm 777

git commands

• git init
• git add
• git commit
• git push
• git log
• git diff
• git status

docker commands

• docker run
• docker ps
• docker logs
• docker start
• docker stop
• docker restart
• docker rm
• docker rmi
• docker pull
• docker exec
• docker image

crontab commands

• crontab -l
• crontab -e
• crontab -u username -l
• crontab -u username -e

iptables commands

• iptables -L
• iptables -A INPUT -i eth0 -p tcp --dport 80 -j ACCEPT
• iptables -D INPUT -i eth0 -p tcp --dport 80 -j ACCEPT

ufw commands

• ufw status
• ufw allow 80/tcp
• ufw deny 80/tcp
• ufw delete allow 80/tcp
• ufw delete deny 80/tcp

ntp commands

• timedatectl status
• timedatectl set-timezone "Asia/Kolkata"
• timedatectl set-ntp true
• timedatectl set-ntp false

sysctl commands

• sysctl -a
• sysctl -p /etc/sysctl.conf

nproc commands

• ulimit -a
• ulimit -n 1000
• ulimit -u 1000
• ulimit -S 1000
• ulimit -H 1000

systemctl commands

• systemctl status
• systemctl start
• systemctl stop
• systemctl restart
• systemctl enable
• systemctl disable
• systemctl list-unit-files
• systemctl list-units

sshd commands

• sshd -t
• sshd -t -f /etc/ssh/sshd_config

vim commands

• :w
• :q
• :q!
• :wq
• :wq!

xfs commands

• mkfs.xfs
• mount
• umount

mkswap commands

• swapon
• swapoff

lv, pv, vg commands

• lvcreate
• lvremove
• vgcreate
• vgremove
• pvcreate
• pvremove

virt-install commands

• virt-install
• virsh list
• virsh start
• virsh stop
• virsh destroy
• virsh console
• virsh attach-device

Conclusion

Here's a summary of my experience with the LFCS exam and additional tips that might help you succeed:

1. Time Management

   • The exam is time-sensitive, so practice completing tasks quickly
   • Skip complex questions initially and return to them later
   • Allocate more time for complex tasks like storage management and container operations
   • Keep track of time - aim to spend no more than 5-7 minutes per question

2. System Navigation

   • Master keyboard shortcuts for faster navigation
   • Keep multiple terminal windows open for different tasks
   • Use tmux or screen for better terminal management
   • Create a quick reference of commonly used paths (/etc/, /var/log/, etc.)

3. Command Line Efficiency

   • Use tab completion extensively
   • Master command history (Ctrl+R for search)
   • Utilize command line aliases for frequent operations
   • Keep command syntax simple and verify before execution

4. Problem-Solving Approach

   • Always verify your work after completing a task
   • If a command fails, check logs immediately (/var/log/)
   • Have multiple approaches ready for each type of task
   • Don't hesitate to use built-in help (man, info, --help)

5. Critical Areas to Focus

   • Storage management (LVM, file systems)
   • Service management with systemd
   • Network configuration and troubleshooting
   • Container operations (especially Docker)
   • User and permission management

Remember: The exam environment is designed to test real-world scenarios. Practice in a non-GUI environment, and focus on understanding the concepts rather than memorizing commands. Good luck!