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🐧 Linux Troubleshooting Scenarios 🐧

🐧 Linux Troubleshooting Scenarios 🐧

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muhammad zubair
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3 min read

Table of contents

When it comes to troubleshooting on Unix/Linux systems, having the right approach is key. Whether you're a Software Developer, DevOps Engineer, or Architect, understanding the problems and their resolutions is vital in this widespread environment.

Let's dive into some common scenarios and their solutions:

Issue 1: Server Connectivity Problem 🔍 Approach / Solution:

  • ✅ Ping server by Hostname and IP Address.

  • ✅ Check if Hostname/IP Address is pingable.

    • ❗ If only IP is pingable, it might be a DNS issue.

      • 📌 Check /etc/hosts, /etc/resolv.conf, and /etc/nsswitch.conf.

      • 📌 Optionally, check DNS in /etc/sysconfig/network-scripts/ifcfg-<interface>.

    • ❗ If neither is pingable, investigate network side or server-specific problems.

      • 📋 Check uptime, IP status, routes, Selinux, and Firewall rules.

      • 🔌 Examine physical cable connections.

Issue 2: Unable to Connect to Website/Application 🔍 Approach / Solution:

  • ✅ Ping server by Hostname and IP Address.

  • ❗ If pingable, use telnet to check service availability.

    • ✅ If service is running, inspect firewall, logs, and configuration.

Issue 3: Unable to SSH 🔍 Approach / Solution:

  • ✅ Ping server by Hostname and IP Address.

  • ❗ If pingable, use telnet to check service availability.

    • ✅ If service is running, verify user status, shell, and root login.

  • 📋 Check service status, firewall, logs, and configuration.

Issue 4: Full Disk Space or Disk Extension 🔍 Approach / Solution:

  • ✅ Detect system performance degradation.

  • ❗ Identify space issues with df and find large files with du.

    • 🗜 Compress/remove large files, move items, check disk health.

    • 📁 Add new disk, create partitions (LVM), extend filesystems.

Issue 5: Corrupted Filesystem 🔍 Approach / Solution:

  • ✅ Check logs for errors causing boot failure.

  • ❗ Run fsck for bad sectors.

    • 🔧 Reboot into rescue mode, fix filesystem, edit fstab entries.

Issue 6: Fstab File Errors 🔍 Approach / Solution:

  • ✅ Check logs for boot errors.

  • ❗ Run fsck for bad sectors.

    • 🔧 Reboot into rescue mode, fix filesystem, edit fstab entries.

Issue 7: Can't cd to Directory 🔍 Approach / Solution:

  • 📋 Check directory existence, path conflicts, permissions, and executability.
  • 📋 Check target existence, path conflicts, permissions, ownership.

Issue 9: Running Out of Memory 🔍 Approach / Solution:

  • 📈 Monitor cache and RAM usage with commands like free -h.

  • ❗ Identify memory-hungry processes, adjust priorities, extend swap space.

Issue 10: Add/Extend Swap Space 🔍 Approach / Solution:

  • ❗ Create swap file, set permissions, enable swap with swapon.

  • 📋 Update fstab for persistence.

Issue 11: Unable to Run Commands 🔍 Approach / Solution:

  • ❗ Troubleshoot permission, sudo access, paths, installation issues.

Issue 12: Unexpected System Reboot and Process Restart 🔍 Approach / Solution:

  • 🔄 Investigate system crash reasons (CPU, RAM, kernel, hardware).

  • 🔁 Understand process restart methods and watchdog applications.

Issue 13: Unable to Get IP Address 🔍 Approach / Solution:

  • 🔌 Check IP assignment methods (DHCP, Static).

  • ❗ Troubleshoot network settings, NIC status, and restart network service.

Issue 14: Backup and Restore File Permissions 🔍 Approach / Solution:

  • 📋 Create ACL file before changing permissions, restore with setfacl.

  • 📸 Consider VM snapshots or rebuilds for restoring permissions.

💡 Useful Disk Partition Tip 💡:

  • 📊 Rescan new disk status with echo 1 > /sys/block/sda/device/rescan.

  • 📝 Expanding existing disks appends space, doesn't affect existing data.

  • 🔄 Recreate filesystems to format old data, share .vmdk for replication.

Mastering Linux troubleshooting helps ensure smooth operations and efficient problem-solving in your IT journey! 🚀🔧

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