Overview
This lecture provides a walkthrough of a common Linux application troubleshooting scenario, highlighting step-by-step problem-solving strategies for technical interviews.
Initial Troubleshooting Steps
- Clarify the operating system and application involved in the issue.
- Ask about the last time the application worked and if other users are affected.
- Inquire about recent updates that could have impacted the application.
Checking for Recent Updates
- Use the apt log to review recent package updates on Linux systems.
- apt is a utility for installing applications and managing updates.
- Log files for apt can be found at
/var/log/apt, specifically history.log.
- Use the grep command to filter log entries by the application's name.
Dependency and Permissions Checks
- Run
sudo apt-get update and sudo apt-get upgrade to ensure all dependencies are installed.
- Attempt to relaunch the application after updating packages.
Investigating File Permissions
- Identify the application's location (e.g., by right-clicking the desktop shortcut).
- Use the
which command to find the application’s binary path.
- Use
cd to navigate to the application's directory.
- Run
ls -l to view file permissions and ownership.
Understanding Permissions Output
- The file permission string (e.g., -rwxr-x---) shows access rights for owner, group, and others.
- Permissions are: r (read), w (write), x (execute).
- Ownership is displayed as owner and group (e.g., root root).
- Lack of execute permission for users prevents them from launching the application.
Resolving Permission Issues
- Use the
chmod command to modify file permissions appropriately.
- After adjusting permissions, test the application again to confirm it works.
Follow-up Actions
- Notify application owners about the issue and resolution to prevent widespread or recurring problems.
- Document findings and the solution process.
Key Terms & Definitions
- apt — Command-line utility for managing packages on Linux systems.
- grep — Command-line tool to search for patterns within text files.
- chmod — Command to change file permissions in Linux.
- ls -l — Command to list files with detailed permissions and ownership.
- Permissions — Access rights assigned to users (read, write, execute).
Action Items / Next Steps
- Practice using Linux troubleshooting commands (apt, grep, chmod, ls -l).
- Review how to interpret and modify Linux file permissions.
- Prepare follow-up questions for clarifying issues during interviews.