Intermediate Questions¶
How to use these interview questions
🧠 Read each question carefully.
Try answering it yourself before expanding the answer to compare with the ideal response.
Level: Intermediate
🟡 Practical Applications & Troubleshooting.
Focus on real-world scenarios, debugging, optimization, and deeper configuration.
1. Which command shows memory usage in Linux?
free -h.
The free command displays free and used memory. The -h flag makes it human-readable (e.g., in GB/MB).
2. How do you check disk usage of mounted filesystems?
df -h.
df (disk free) shows available disk space on file systems.
3. Which command checks the size of a directory and its contents?
du -sh [directory].
du (disk usage) estimates file space usage. -s summarizes the total, and -h makes it human-readable.
4. Which command displays running processes in real-time?
top (or htop).
top provides a dynamic view of system processes, CPU usage, and memory consumption.
5. How do you list all running processes via the command line?
ps aux.
This shows a snapshot of all potential processes (a), associated with a terminal or not (x), and the user initiating them (u).
6. Which command sends a signal to stop a process?
kill [PID].
By default, it sends SIGTERM (15) to ask the process to stop gracefully. Use kill -9 [PID] for SIGKILL (force kill).
7. What is a Zombie process?
A process that has completed execution but still has an entry in the process table.
It happens when the parent process hasn't read the child's exit status. You can see them as Z in top or ps.
8. Which command manages system services (start, stop, enable)?
systemctl.
For example: systemctl status nginx, systemctl start nginx, systemctl enable nginx.
9. How do you add a new user to the system?
useradd -m [username].
The -m flag creates the user's home directory. You should then set a password using passwd [username].
10. Which file contains user account information?
/etc/passwd.
It stores username, UID, GID, home directory, and default shell. Passwords are stored securely in /etc/shadow.
11. How do you give a user sudo privileges?
Add them to the wheel group (RHEL/CentOS) or sudo group (Ubuntu/Debian).
Command: usermod -aG sudo [username].
12. What is the difference between su and su -?
su switches user but keeps the current shell environment variables.
su - switches user and loads that user's full login environment (fresh shell).
13. Which command is used to edit the /etc/sudoers file safely?
visudo.
It locks the file and checks for syntax errors before saving, preventing you from locking yourself out of root access.
14. How do you search for a specific package to install?
yum search [package] (RedHat) or apt search [package] (Debian).
Package managers allow you to query repositories for available software.
15. Which command installs a package?
yum install [package] or apt install [package].
You typically need sudo privileges to run these commands.
16. What is the PATH environment variable?
A list of directories where the shell looks for executable commands.
When you type ls, the shell checks folders in $PATH to find the ls binary.
17. How do you make an alias for a command?
alias name='command'.
For example: alias ll='ls -la'. To make it permanent, add it to your ~/.bashrc.
18. Which command is used to identify the location of valid executables?
which [command].
For example, which python tells you the path to the python binary that will be executed.
19. Which command enables a service to start automatically at boot?
systemctl enable [service-name].
This creates a symlink in the systemd directory structure to auto-start the service.
20. How do you lock a user account?
passwd -l [username] or usermod -L [username].
This prevents the user from logging in with a password.
🧪 Ready to test yourself?¶
👉 Take the Linux File & Directory Quiz 👉 Take the Linux System & Disk Quiz 👉 Take the Linux Process Management Quiz
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