LFCS Certification Cheat Sheet 2026

The 30 highest-yield LFCS Certification facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which command shows which installed RPM packages have files that have been modified since installation? → rpm -Va
2. Which input must be given to ifconfig in order to turn on a network interface that was previously inactive? → up
3. In which file do you persistently add custom kernel parameters on systemd-based systems using GRUB 2? → /etc/default/grub
4. In nftables, what command adds a new table named 'mytable' with the inet family? → nft add table inet mytable
5. Which of the following is a key advantage of using a high-level package manager like `dnf` or `apt` compared to a low-level tool like `rpm` or `dpkg`? → They automatically resolve and install required software dependencies from repositories.
6. How do you stream new journal entries in real time, similar to `tail -f`? → journalctl -f
7. A process runs as UID 1001. A file has owner UID 1001 and permissions '---rwxrwx'. Can the owner read the file? → No — the kernel checks only the owner bits, which are '---'
8. After chrooting into /sysroot to reset the root password on an SELinux system, which command ensures file contexts are relabeled on next boot? → touch /.autorelabel
9. Which dpkg command extracts the contents of a .deb file without installing it? → dpkg-deb -x package.deb /target
10. Where should application-specific logrotate configuration files be placed? → /etc/logrotate.d/
11. A user's umask is 027. What permissions will a newly created regular file have? → 640
12. Which rsyslog rule forwards all facility/severity combinations to a remote UDP syslog server at 192.168.1.1? → *.* @192.168.1.1
13. What is the role of `/etc/apt/preferences` or `/etc/apt/preferences.d/` on Debian systems? → Defines package pinning rules that control which version APT installs
14. How do you configure a system to use a local directory as a YUM repository? → Create a .repo file in /etc/yum.repos.d/ with baseurl=file:///path
15. What does the `rpm -e --nodeps ` command do? → Removes a package while ignoring dependency checks
16. Which directive in an SSH server configuration (/etc/ssh/sshd_config) disables password-based logins? → PasswordAuthentication no
17. Which `dpkg` command displays the current state (installed, removed, etc.) of all packages on the system? → dpkg --get-selections
18. Which special permission bit, when set on an executable, causes it to run with the group privileges of the file's group rather than the invoking user's group? → Setgid (chmod g+s)
19. What command prints kernel ring buffer messages, often used to diagnose hardware detection during boot? → dmesg
20. Which command would set the setuid bit on an executable 'myapp' using symbolic notation? → chmod u+s myapp
21. When a `yum update` is run and a package update breaks an application, what is the correct approach to revert? → Use `yum history undo ` to roll back the specific update transaction
22. What does 'umask 0022' mean when a user creates a new directory? → The directory gets permissions 755 (777 minus 022)
23. Which systemctl command displays the current state of a service, including its active state, PID, and recent log lines? → systemctl status sshd
24. Which command would display numeric UIDs/GIDs instead of names in an ACL listing? → getfacl -n file.txt
25. Which special variable holds the exit status of the most recently executed command? → $?
26. A service unit file contains `Type=forking`. What does this mean? → The parent process exits after forking a child, and the child becomes the main process
27. Which journalctl option shows entries logged after a specified time, such as 'yesterday' or '2 hours ago'? → --since
28. How do you immediately switch to rescue.target on a running system without rebooting? → systemctl isolate rescue.target
29. Which directive in a [Service] section tells systemd to restart a service whenever it exits, regardless of exit code? → Restart=always
30. Which `rpm` command rebuilds the RPM database after it becomes corrupted? → rpm --rebuilddb