Linux Interview Questions — All Categories
20 questions tagged with Linux as a technology, across every category it appears in
A backup script runs perfectly when you execute it by hand, but fails silently every night when cron runs it. How would you debug it?
BeginnerBashLinux8 min
What's actually the difference between a container and a virtual machine, at the operating system level — not the marketing-slide version?
BeginnerContainersLinux7 min
What specific Linux namespace types exist, and what does each one actually isolate for a containerized process?
IntermediateLinuxContainers7 min
What actually changed between cgroups v1 and v2, and why did some container resource limit behavior change when a host migrated to a v2-only kernel/distro?
AdvancedContainersLinux7 min
A container keeps getting killed, and both the container's own memory limit and the host's overall available memory look potentially responsible. How do you determine which one actually caused it?
AdvancedContainersLinux7 min
How does a container image's layered filesystem actually work at the OS level — what makes writes inside a running container not modify the underlying image?
IntermediateContainersLinux6 min
Your containerized application's process count keeps growing over time, even though nothing appears to be leaking connections or memory. What's likely happening, and why is it specific to running in a container?
AdvancedContainersLinux7 min
How would you build automated alerting specifically for the df/du divergence pattern, rather than relying on someone noticing it during an incident?
IntermediateLinuxPrometheus6 min
df says a server's disk is 100% full, but running du -sh on every top-level directory only adds up to a fraction of that. Where did the rest of the space go?
IntermediateLinux8 min
How would you find the same df/du phantom-disk-usage issue on a containerized workload, where the culprit process might be in a different mount namespace?
AdvancedLinuxDocker8 min
Why does Unix allow you to delete a file that's still open by a running process, instead of blocking the delete like some other operating systems do?
IntermediateLinux6 min
chmod 755 vs chmod 644 — what do these numbers actually mean, and how would you figure out the right mode for a new file without guessing?
BeginnerLinux6 min
A containerized process shows only 40% average CPU usage, well under its configured limit, but application metrics show frequent latency spikes correlating with CPU throttling events. How is this possible?
AdvancedLinuxKubernetes8 min
A server's load average shows 8.0 on a 4-core machine, but CPU usage in top only shows 20%. How can load be double the core count while CPU usage looks low?
IntermediateLinux7 min
A service takes 25 seconds to shut down gracefully, but your orchestrator sends SIGKILL after a 10-second grace period, causing corrupted in-progress writes on every deploy. How do you actually fix this?
IntermediateLinux7 min
A production process appears to be running (it's in the process list, consuming no CPU) but isn't responding to any requests. How would you use strace to figure out what it's actually doing?
AdvancedLinux8 min
A misbehaving service is stuck in a rapid restart loop, consuming CPU and flooding logs, because systemd keeps restarting it immediately after every crash. How would you configure this correctly?
IntermediateLinuxSystemd6 min
A service running fine for months suddenly throws 'Too many open files' errors under increased load. How do you fix it correctly, rather than just raising the limit blindly?
IntermediateLinux7 min
How does debugging a systemd timer failure differ from debugging the same issue in cron?
IntermediateLinuxSystemd7 min
An application intermittently fails to resolve a hostname — most requests succeed, but a small percentage fail with a DNS error. How would you track this down?
IntermediateDNSLinux8 min