Linux Troubleshooting and Commands
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1
What are the four main troubleshooting steps?
Identify the issue, isolate the cause, apply a safe fix, then verify and document.
2
What should you ask first when a system goes down?
What is affected, who is affected, when it started, and what changed recently?
3
Linux: What does df -h do?
Shows disk usage and available space for mounted filesystems in readable units.
4
Linux: What does du -sh /var/log do?
Shows the total disk space used by the /var/log directory.
5
What is the difference between df and du?
df checks filesystem free space; du checks how much space files or directories use.
6
How do you troubleshoot a nearly full Linux disk?
Use df -h to find the full filesystem, du to find large directories, then investigate before deleting.
7
Linux: What does free -h show?
RAM and swap usage in human-readable units.
8
Linux: What is the difference between top and ps aux?
top updates processesource usage live; ps aux displays a snapshot of processes.
9
Linux: How do you check a service status?
systemctl status <service>
10
Linux: How do you read logs for a service?
journalctl -u <service>
11
Linux: How do you find IP addresses?
ip addr
12
Linux: How do you find listening TCP/UDP ports?
ss -tuln
13
Linux: What do chmod and chown do?
chmod changes permissions; chown changes file ownership.
14
Linux: What does df -i check?
Inode usage; a filesystem can run out of inodes even with free disk space.
15
A Linux server is slow. What would you check?
Scope, top for CPU/processes, free -h for memory, df -h for disk, and relevant logs.
16
A Linux service is down. How do you troubleshoot?
Check systemctl status, journalctl logs, configuration, dependencies, and ports; fix and verify.
17
Why not restart a production server immediately?
It may interrupt users and hide the root cause; investigate and follow change procedures first.
18
Windows: What does ipconfig /all show?
IP address, gateway, DNS servers, DHCP information, and adapter configuration.
19
Windows: How do you check services with PowerShell?
Get-Service; use Get-Service -Name <name> for a specific service.
20
Windows: How do you check disk capacity with PowerShell?
Get-Volume
21
Windows: What is Event Viewer?
A tool to inspect Windows system, security, and application event logs.
22
What is Active Directory (AD)?
A directory service that centrally manages Windows domain identities and computers.
23
What is a domain controller?
A server that provides Active Directory authentication and directory services.
24
What is a Group Policy Object (GPO)?
A set of centrally managed Windows user and computer configuration settings.
25
What is an Organizational Unit (OU)?
An AD container used to organize objects, delegate management, and scope Group Policy.
26
How is AD different from Microsoft Entra ID?
AD manages Windows domains; Entra ID manages cloud identities and application access.
27
A user cannot access a shared folder. What do you check?
Connectivity, authentication, group membership, share permissions, and NTFS permissions.
28
What does DNS do?
Resolves hostnames into IP addresses.
29
What does DHCP do?
Automatically assigns IP configuration, including gateway and DNS settings.
30
What does a default gateway do?
Routes traffic from a local subnet toward other networks.
31
What is a VLAN?
A logical Layer 2 network segment that separates broadcast domains.
32
What is the difference between a switch and a router?
A switch connects devices within a LAN; a router forwards traffic between IP networks.
33
What is the difference between TCP and UDP?
TCP is reliable and ordered; UDP has lower overhead but no built-in delivery guarantee.
34
Which ports should an IT intern recognize?
SSH 22, DNS 53, HTTP 80, HTTPS 443, SMB 445, and RDP 3389.
35
A site works by IP but not by name. Suspect what?
DNS; inspect configured DNS servers and test with nslookup.
36
How do you troubleshoot a server that is unreachable?
Check scope, IP connectivity, DNS, routes, firewalls, service ports, and server health.
37
What is a firewall?
A control that permits or blocks network traffic based on rules.
38
What is hybrid infrastructure?
Infrastructure combining on-premises systems with cloud services.
39
AWS EC2 is equivalent to what in Azure?
Azure Virtual Machines; both provide virtual servers.
40
AWS S3 is most similar to what in Azure?
Azure Blob Storage; both provide object storage.
41
AWS VPC is similar to what in Azure?
Azure Virtual Network (VNet); both provide isolated virtual networking.
42
What does an AWS security group do?
Acts as a stateful virtual firewall controlling permitted traffic to AWS resources.
43
What are CloudWatch and Azure Monitor used for?
Collecting metrics, logs, and alerts to monitor and troubleshoot resources.
44
What is IAM?
Identity and Access Management: controlling identities and their permissions.
45
What is RBAC?
Role-Based Access Control: permissions assigned through roles.
46
What is least privilege?
Giving users and services only the permissions needed for their tasks.
47
What is authentication vs. authorization?
Authentication verifies identity; authorization determines allowed actions.
48
An AWS EC2 instance is unreachable. What do you check?
Instance state/status, IP and routes, security groups, NACLs, OS firewall, and services.
49
An AWS instance costs too much. What do you do?
Review utilization and billing, check sizing and idle resources, then propose approved changes.
50
What is a hypervisor?
Software that runs and manages virtual machines on physical hardware.
51
What is Nutanix AHV?
An enterprise hypervisor platform for running and managing virtual machines.
52
What is Cohesity used for?
Enterprise data protection, backups, and recovery.
53
VM vs. container: What is the difference?
A VM has a guest OS; a container isolates an app while sharing the host OS kernel.
54
What is the difference between a snapshot and a backup?
A snapshot captures a point-in-time state; a backup preserves a separately recoverable copy.
55
What does RPO mean?
Recovery Point Objective: maximum acceptable data loss, measured in time.
56
What does RTO mean?
Recovery Time Objective: maximum acceptable time to restore service.
57
What is RAID?
Combines physical disks for redundancy and/or performance; it does not replace backups.
58
What is Infrastructure as Code (IaC)?
Defining and provisioning infrastructure through code or configuration files.
59
Terraform vs. CloudFormation?
Terraform supports multiple providers; CloudFormation provisions AWS resources.
60
What does terraform plan do?
Previews proposed changes without applying them.
61
What would you automate as an infrastructure intern?
Safe repetitive tasks like disk alerts, service checks, inventory reports, or documentation.
62
How should you use AI in enterprise IT operations?
Use approved tools for scripts, log summaries, or docs; verify outputs and protect sensitive data.
63
Tell me about yourself: what 3 points matter?
Cybersecurity student with Security+/Network+; hands-on AWS/AD/Linux labs; eager to support infrastructure.
64
How would you describe your AWS Wazuh project?
Deployed Wazuh on Ubuntu EC2, configured monitoring and custom SSH/FIM rules; learned cloud and Linux operations.
65
How would you describe your Active Directory project?
Built an AD lab to learn domain authentication, service accounts, permissions, and Windows administration.
66
Why infrastructure if your degree is cybersecurity?
Security sparked my interest in how systems operate; I want practical experience maintaining them.
67
Why InterDigital?
Its wireless/video/AI research and hybrid infrastructure make cloud, troubleshooting, and automation meaningful.
68
What if you do not know an interview answer?
Be honest; explain how you would narrow the problem, consult documentation, test, and ask for help.
69
What should you ask at the end of the interview?
What would success look like in three months, and which projects could I contribute to?
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