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1. CPU and Memory Usage
- top
-d: Specify the delay time between screen updates.-u <user>: Display processes belonging to a specific user.
- htop
- F6: Sort by various criteria including CPU, memory.
- F5: Toggle tree view.
- vmstat
1: Display statistics every second.-s: Show event counters and memory statistics.
2. Disk Usage
- df
-h: Human-readable format, showing sizes in KB, MB, or GB.-T: Include filesystem type in the output.
- du
-h: Human-readable format.-a: Include all files, not just directories.
- iostat
-x: Display extended statistics.-d: Display disk utilization only.
3. Network
- netstat
-tuln: Display TCP/UDP listening ports.-p: Show the PID and name of the program to which each socket belongs.
- ss
-t -a: Display all TCP sockets.-u -a: Display all UDP sockets.
- iftop
-i <interface>: Specify network interface.-n: Do not resolve hostnames (faster display).
- nload
-m: Display multiple devices at once.-t <interval>: Set the refresh interval in milliseconds.
- ping
-c <count>: Number of echo requests to send.-i <interval>: Interval between sending each packet.
4. Process Monitoring
- ps
-aux: Show all processes for all users.-eH or --forest: Display processes in a hierarchy.
- pstree
-p: Show PIDs.-u: Show usernames.
5. System Activity Reporter (sar)
-r: Report memory utilization.-n DEV: Report network statistics.-d: Report disk activity.-u: Report CPU utilization.
6. Performance Analysis
- perf
stat: Gather performance counters for a command.record: Record events for later analysis.report: Analyze and report performance data.
- strace
-f: Trace child processes.-e trace=<syscall>: Trace specified system calls.
7. Monitoring Files and Directories
- inotifywait
-m: Monitor events indefinitely instead of exiting after the first event.-r: Recursively watch all directories and subdirectories.
- inotifywatch
-t <seconds>: Run for a specified number of seconds before exiting.-r: Recursively watch all directories and subdirectories.
