System Maintence Tools

1. Uptime# at 2,5,15 minutes
2. top - all about processes
3. vmstat
4. free

Uptime

top - all about processes

• us : time running un-niced user processes
• sy : time running kernel processes
• ni : time running niced user processes
• id : time spent in the kernel idle handler
• wa : time waiting for I/O completion
• hi : time spent servicing hardware interrupts
• si : time spent servicing software interrupts
• st : time stolen from this vm by the hypervisor

• PR: Priority
• NI: Nice
• VIRT: Virtual Memory Size (KiB) of task
• RES: Resident Memory Size (KiB) i.e. non swapable. A subset VIRT
• SHR: Shared Memory Size (KiB). A subset RES
• S: Process Status
  • D = uninterruptible sleep
  • I = idle
  • R = running
  • S = sleeping
  • T = stopped by job control signal
  • t = stopped by debugger during trace
  • Z = zombie
• %CPU: CPU Usage
• %MEM: Memory Usage

vmstat

• r: The number of runnable processes (running or waiting for run time).
• b: The number of processes blocked waiting for I/O to complete.
Memory
• These are affected by the --unit option.
• swpd: the amount of swap memory used.
• free: the amount of idle memory.
• buff: the amount of memory used as buffers.
• cache: the amount of memory used as cache.
• inact: the amount of inactive memory. (-a option)
• active: the amount of active memory. (-a option)
• Swap
  si: Amount of memory swapped in from disk (/s). so: Amount of memory swapped to disk
• IO
  bi: Kibibyte received from a block device (KiB/s). bo: Kibibyte sent to a block device (KiB/s).
• System
  in: The number of interrupts per second, including the clock. cs: The number of context switches per second.
• CPU
  These are percentages of total CPU time. us: Time spent running non-kernel code. (user time, including nice time) sy: Time spent running kernel code. (system time) id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time. wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle. st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown. gu: Time spent running Kernel-based Virtual Machine (KVM) guest code (guest time, including guest nice).

free