Top 25 Must-Know Ubuntu OS Programming Interview Questions in 2023

Landing a programming job working with Ubuntu OS requires strong technical skills and the ability to ace tricky interview questions. I’ve compiled this list of the top 25 Ubuntu programming interview questions to help you prepare and stand out from other candidates. Whether you’re an experienced Linux developer or just starting out, reviewing these questions can help sharpen your skills and confidence Let’s dive in!

1. What are the key differences between Debian and Ubuntu?

• Ubuntu is based on Debian but has a more frequent release schedule (every 6 months) vs Debian’s 2+ years.
• Ubuntu focuses on desktop and servers while Debian targets a universal OS.
• Ubuntu has its own Unity interface while Debian uses the GNOME desktop.
• Ubuntu has more proprietary software included by default like browser plugins.

2. How does Ubuntu handle package management and software installation?

Ubuntu uses Debian’s APT (Advanced Packaging Tool) and dpkg for package management. Key things to know:

• APT handles dependency resolution, retrieving packages from repositories, installation/removal
• dpkg is the lower level tool that unpacks and installs .deb packages
• apt-get, apt-cache, aptitude are common frontends to APT
• Snap packages provide sandboxed cross-distro apps
• PPAs (Personal Package Archives) allow installing custom software builds

3. What are some key factors to optimize performance in Ubuntu?

Some optimize tricks

• Use a lightweight desktop environment like Xfce or MATE
• Disable unnecessary startup services
• Upgrade to an SSD if using a HDD
• Add swap space if RAM is under 4GB
• Use Ubuntu’s built-in system monitor to check for resource hogs

4. How can you customize Ubuntu’s GNOME desktop environment?

Some customization options:

• Change wallpaper, themes, icon sets via Settings or Tweaks
• Install GNOME extensions to add functionality
• Modify system-wide defaults using gsettings commands
• Tweak fonts, UI animations, icon sizes in dconf-editor
• Switch to a different shell like bash, csh, zsh

5. What are some key Linux commands for managing storage?

Essential storage commands include:

• fdisk, cfdisk – Partition disks
• mkfs – Create filesystems
• mount/umount – Mount/unmount volumes
• fsck – Check and repair filesystems
• du, df – Check disk space usage
• rsync – Sync files between dirs/servers
• ln – Create hard and soft links

6. How can you obtain info about the OS, hardware, and processes in Ubuntu?

Useful info commands

• uname – Get kernel name and version
• lsb_release – Print Ubuntu version info
• lscpu – CPU architecture details
• lsusb, lspci – List USB and PCI devices
• dmidecode – BIOS and hardware details
• htop – Interactive process viewer
• ps – Snapshot of running processes

7. What are some key security measures to implement on an Ubuntu server?

Some good security practices:

• Use SSH with key-based authentication
• Setup a firewall with ufw or iptables
• Enable unattended-upgrades for security patches
• Restrict sudo access to admin users
• Install fail2ban to block brute force attacks
• Disable root login and password auth in SSH config

8. How can you debug application issues in Ubuntu?

Helpful debugging tools:

• journalctl – View logs from systemd services
• dmesg – Kernel ring buffer information
• strace – Trace system calls of a process
• lsof – List open files and processes using them
• pstack – Stack traces of all threads in a process
• gdb – Debug applications interactively

9. What are the differences between an apt repository and a PPA?

APT repositories contain Ubuntu’s officially supported packages. PPAs or Personal Package Archives contain packages built by third-party developers and organizations.

Key differences:

• Repositories are fully supported, PPAs are not
• Repos use HTTPS, PPAs use HTTP
• Repos are hosted by Canonical, PPAs are hosted elsewhere
• PPAs make it easy to install custom software builds

10. How can you modify network configurations in Ubuntu?

You can configure networking:

• Using the graphical utility nm-connection-editor
• Editing files under /etc/netplan for Netplan networks
• Modifying ifupdown files under /etc/network/ for older configs
• Using ip, ifconfig and route commands directly

The NetworkManager daemon manages connections dynamically across tools.

11. What are some standard file permissions in Linux?

Common file permissions:

• 755 for executables
• 644 for configuration files
• 600 for sensitive data files
• 775 for group-writable dirs like /var/www
• 700 for private user dirs like /home/user

Permissions are managed using the chmod command or via the file manager GUI.

12. How can you find information about a command in Ubuntu?

Find usage info with:

• man – Manual pages for commands
• info – More detailed documentation
• command –help – Quick built-in help
• which – Show full path of command binary
• type – Show whether shell builtin, alias or executable

13. What are the differences between apt and apt-get?

Both tools are frontends to APT for package management. Key differences:

• apt is the newer high-level CLI utility
• apt-get is older but still more feature rich
• apt is simpler – just apt install vs apt-get install
• apt has a progress bar and colorized output
• apt-get has more options like downloading only

14. How do you manage services in Ubuntu?

• Services can be enabled/disabled using systemctl
• service and invoke-rc.d tools can control SysV init scripts
• update-rc.d sets init scripts to start at boot
• Services can be manually started/stopped with their init script
• systemd is Ubuntu’s default init system which manages services

15. What are some key commands for user management in Linux?

User management commands:

• useradd – Create new users
• usermod – Modify users
• userdel – Delete users
• passwd – Change passwords
• chage – Modify password expiration
• gpasswd – Manage group memberships

16. How do you check the Ubuntu version you are running?

Some ways to check your version:

• lsb_release -a – Print all version info
• cat /etc/os-release – View OS release metadata
• cat /etc/lsb-release – Print LSB version info
• uname -m – Print system architecture
• hostnamectl – Show hostname, OS, kernel

17. Explain how sudo works in Ubuntu?

• sudo allows running commands as other users, by default root
• It requires the user’s password for elevated access
• /etc/sudoers file controls who can use sudo
• Users can be granted full sudo access or allowed certain commands
• sudo remembers credentials for a timeout period (15 min default)

18. How can you install Ubuntu without affecting the existing OS?

Some ways to dual boot Ubuntu:

• Install to a separate partition with manual disk partitioning
• Use a flash drive or external HDD with a “live” Ubuntu imaged
• Set up a virtual machine with VirtualBox, VMware, etc and install Ubuntu on it
• Use the Windows Subsystem for Linux to get an Ubuntu environment

19. How does Ubuntu implement process isolation and sandboxing for security?

Some isolation techniques used:

• AppArmor – Kernel enhancements like mediating syscalls
• Seccomp – Filter access to Linux syscalls
• Snappy – Next-gen Ubuntu Core uses snap packages for app isolation
• LXC – Linux containers provide lightweight virtualization
• SELinux – Implements mandatory access controls

20. Explain how to repair a corrupted filesystem in Ubuntu.

To fix filesystem errors:

• Unmount the affected partition
• Run fsck to check/repair from a live CD/USB
• Use the -y option to automatically repair issues
• Check dmesg and logs for details on the errors
• Backup data and reinstall as needed for severe corruption

21. How can you configure networking with Netplan in Ubuntu?

Netplan basics:

• Uses YAML config files under /etc/netplan
• Defines networks, interfaces, addresses, DNS, etc
• Uses renderer like NetworkManager or systemd-networkd
• netplan generate creates backend configs
• netplan apply applies the new config

22. What are some common use cases for Snappy and Snap packages?

Snaps are self-contained, auto-updating app packages. Common uses:

• Distribute desktop apps across Linux distros
• Deliver IoT and cloud apps
• Package server and CLI utilities