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Basic Linux Administration
- User Management: A user complains they cannot log in. How will you troubleshoot?
– Check if the user account exists:
grep username /etc/passwd
– Verify password expiration:
chage -l username
– Check authentication logs:
tail -f /var/log/auth.log
– Ensure home directory permissions:
ls -ld /home/username
- File Permissions: A script is executable by one user but not another. How do you resolve this?
– Check file permissions:
ls -l script.sh
– Modify permissions:
chmod 755 script.sh
– Verify group ownership:
chown :groupname script.sh
- Process Management: A service is consuming 100% CPU. How will you find and fix it?
– Identify high-CPU processes:
top ps aux --sort=-%cpu | head
– Kill the problematic process:
kill -9 PID
- SSH Issues: You cannot SSH into a remote machine. How do you debug?
– Check SSH service status:
systemctl status sshd
– Verify firewall rules:
iptables -L
– Test SSH connectivity:
ssh -v user@remote_host
You Should Know:
- Disk Space Full: / Partition is Full. How Do You Find and Delete Large Files Safely?
– Find large files (>100MB):
find / -type f -size +100M -exec ls -lh {} \;
– Delete safely (after confirmation):
rm -rf /path/to/large_file
- File Corruption: A Log File is Showing Junk Characters. How Will You Check and Recover It?
– Check file integrity:
file /var/log/syslog
– Attempt recovery:
strings /var/log/syslog > recovered_log.txt
- Crontab Not Running: A Scheduled Job is Not Executing. How Do You Debug?
– Check cron logs:
grep CRON /var/log/syslog
– Verify crontab entries:
crontab -l
- Package Installation Failing: YUM or APT is Failing. How Will You Resolve It?
– For Debian/Ubuntu:
sudo apt update && sudo apt upgrade
– For RHEL/CentOS:
sudo yum clean all && sudo yum update
What Undercode Say:
Linux troubleshooting requires familiarity with logs, permissions, and system monitoring. Always verify before deleting files, and use `journalctl` for systemd-based debugging. Automation (cron, systemd timers) must be logged properly.
Expected Output:
A structured guide with verified commands for Linux troubleshooting.
(Note: Telegram and WhatsApp URLs were removed as per instructions.)
References:
Reported By: Mohamed Abdelgadr – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
