System Logs and Performance Tuning

System Logs Analysis

• Location of Logs:

  • /var/log/: Primary directory for system logs.
  • Common log files:
    • syslog: General system messages.
    • dmesg: Boot and kernel messages.
    • auth.log: Authentication logs.
    • kern.log: Kernel messages.

• Log Management Tools:

  • journalctl: Command to query and display logs from systemd journal.
  • logrotate: Tool to manage log file sizes and archival.

• Analyzing Logs:

  • Use grep for searching specific entries.
  • tail -f: Monitor log files in real-time.
  • Check for patterns indicating issues (e.g., repeated errors).

Performance Tuning

• Monitoring Tools:

  • top: Displays real-time system statistics.
  • htop: Enhanced version of top with a user-friendly interface.
  • vmstat: Reports on virtual memory, processes, and CPU activity.
  • iostat: Monitors input/output device and CPU performance.

• Common Tuning Techniques:

  • Adjust swappiness: Controls the balance between RAM and swap usage.
  • Optimize file system: Use tune2fs for ext2/3/4 filesystems.
  • Configure caching: Adjust settings for cachepressure and dirty_ratio.

• CPU and Memory Management:

  • Use nice and renice to prioritize processes.
  • Monitor memory usage with free and adjust applications accordingly.

Package Management

• Package Managers:

  • apt: Used in Debian-based distributions (e.g., Ubuntu).
  • yum/dnf: Used in Red Hat-based distributions (e.g., CentOS, Fedora).

• Common Commands:

  • Install: apt install package_name or yum install package_name.
  • Update: apt update and apt upgrade or yum update.
  • Remove: apt remove package_name or yum remove package_name.

• Dependency Management:

  • Package managers handle dependencies automatically but may require manual resolution in some cases.

Network Troubleshooting

• Basic Tools:

  • ping: Tests network connectivity.
  • traceroute: Traces the path packets take to a network destination.
  • ifconfig/ip addr: Displays and configures network interfaces.
  • netstat: Shows active connections and routing tables.

• DNS Troubleshooting:

  • nslookup/dig: Queries DNS records.
  • Check /etc/resolv.conf for DNS server configuration.

• Firewall Configuration:

  • iptables/firewalld: Tools to manage firewall rules and network traffic.

Backup And Recovery

• Backup Tools:

  • rsync: Efficient file transfer and synchronization tool.
  • tar: Archive and compress files.
  • dd: Used for disk cloning and backup.

• Backup Strategies:

  • Full Backup: Complete system backup.
  • Incremental Backup: Backs up only the changes since the last backup.
  • Differential Backup: Backs up changes since the last full backup.

• Recovery Process:

  • Ensure backup integrity by regularly testing recovery procedures.
  • Use live CD/USB for recovery in case of system failure.
  • Keep backups in a separate location to protect against hardware failure or disasters.

System Logs Analysis

• System logs are primarily located in the /var/log/ directory, which includes essential log files:
  • syslog for general system messages
  • dmesg for boot and kernel messages
  • auth.log for authentication logs
  • kern.log for kernel messages
• journalctl is used to query logs from the systemd journal, while logrotate helps manage log sizes and archival.
• Analyzing logs can involve:
  • The grep command for searching specific entries
  • tail -f for real-time log monitoring
  • Identifying patterns that indicate recurring issues, such as repeated error messages

Performance Tuning

• Monitoring system performance can be accomplished using:
  • top for real-time system statistics
  • htop for a user-friendly interface version of top
  • vmstat for insights on virtual memory, processes, and CPU activity
  • iostat to monitor device and CPU performance
• Common tuning techniques include:
  • Adjusting swappiness to balance RAM and swap usage
  • Optimizing the file system with tune2fs for ext2/3/4 filesystems
  • Modifying caching settings like cachepressure and dirty_ratio
• CPU and memory management can be handled with:
  • nice and renice for prioritizing processes
  • free command to monitor memory usage and adjust application resource utilization

Package Management

• Key package managers include:
  • apt for Debian-based distributions (e.g., Ubuntu)
  • yum and dnf for Red Hat-based distributions (e.g., CentOS, Fedora)
• Essential commands for package management:
  • Installation: apt install package_name or yum install package_name
  • Updates: apt update and apt upgrade or yum update
  • Removal: apt remove package_name or yum remove package_name
• Package managers typically handle dependencies automatically but may require manual intervention in some instances.

Network Troubleshooting

• Basic networking tools include:
  • ping for testing network connectivity
  • traceroute to identify the path packets take to a destination
  • ifconfig or ip addr for displaying and configuring network interfaces
  • netstat to show active connections and routing tables
• For DNS troubleshooting:
  • nslookup and dig are used to query DNS records
  • Verify DNS server configurations in /etc/resolv.conf
• Firewall configuration can be managed with:
  • iptables or firewalld for setting firewall rules and controlling network traffic

Backup And Recovery

• Key backup tools consist of:
  • rsync for efficient file transfer and syncing
  • tar for archiving and compressing files
  • dd for disk cloning and backup
• Common backup strategies include:
  • Full Backup: Comprehensive system backup
  • Incremental Backup: Captures only the changes since the last backup
  • Differential Backup: Backs up changes since the last full backup
• Recovery processes should ensure backup integrity through regular testing of recovery procedures, utilizing live CD/USB for recovery efforts, and storing backups in separate locations to mitigate risks of hardware failures or disasters.