Top 10 Linux Commands for Monitoring and Troubleshooting Your System

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1. Disk and File System Checks

Objective:

Monitor disk usage and verify file system configurations.

Commands and Steps:

 

1.     View Disk Space Usage:

Command: df -h

Verify the available and used space in a human-readable format.

 

2.     Check File System Configurations:

Command: cat /etc/fstab

Ensure all required file systems are configured to mount at boot.

 

3.     Verify Permissions of fstab File:

Command: ls -ld /etc/fstab

Check permissions to ensure security and avoid unauthorized changes.

2. Network Configuration and Connectivity

Objective:

Validate DNS configurations and network routes.

Commands and Steps:

 

1.     Verify DNS Resolver Permissions:

Command: ls -ld /etc/resolv.conf

 

2.     Display DNS Server Configuration:

Command: cat /etc/resolv.conf

 

3.     Check Kernel Routing Table:

Command: ip route

Confirm active routes for network connectivity.

3. System Information

Objective:

Gather details about the system and verify date/time settings.

Commands and Steps:

 

1.     Detailed System Information:

Command: uname -a

2.     Kernel Version:

Command: uname -r

3.     Date and Time Verification:

Command: date

4. User and Group Configurations

Objective:

Ensure proper permissions and verify user/group details.

Commands and Steps:

 

1.     Check Permissions of Key Files:

Command: ls -ld /etc/passwd /etc/group /etc/hosts

 

2.     Display User Accounts:

Command: cat /etc/passwd

 

3.     Show Group Definitions:

Command: cat /etc/group

 

4.     Verify Host-to-IP Mappings:

Command: cat /etc/hosts

5. Scheduled Jobs

Objective:

Verify cron jobs for automation.

Commands and Steps:

 

1.     List Scheduled Cron Jobs:

Command: crontab -l

6. Process Monitoring

Objective:

Monitor critical services and processes.

Commands and Steps:

 

1.     Check for Specific Processes:

FTP: ps -ef | grep ftp

VNC: ps -ef | grep vnc

Agents: ps -ef | grep agent

Oracle PMON: ps -ef | grep pmon

Oracle Listener: ps -ef | grep tns

7. Mail Service Checks

Objective:

Ensure proper functioning of mail services.

Commands and Steps:

 

1.     Verify Postfix Permissions:

Command: ls -ld /etc/postfix

2.     List Mail Queue Files:

Command: ls -ltr /var/spool/postfix

3.     Check Postfix Service:

Command: ps -ef | grep postfix

4.     Audit Mail Directory:

Command: ls -ltr /etc/mail/

5.     Verify Sendmail Service:

Command: ps -ef | grep sendmail

8. Resource Utilization

Objective:

Monitor system resource usage.

Commands and Steps:

1.     CPU Details:

Command: lscpu

2.     Memory Usage in GB:

Command: free -g

3.     System Limits:

Hard Limits: ulimit -aH

Soft Limits: ulimit -aS

4.     Default File Permissions Mask:

Command: umask

9. Printer Services

Objective:

Monitor printer status and jobs.

Commands and Steps:

 

1.     Check Printer Status:

Command: lpstat -a

10. Library Dependencies

Objective:

Verify critical library files.

Commands and Steps:

 

1.     Check File Presence and Permissions:

Command: ls -ld /usr/lib/libgtk-x11-2.0.so.0

Related Posts:

Linux Mount and Umount file system in linux

Frequently Used Linux Commands for System & Oracle DBA Operations

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