Posts tagged htop

linux: systemcheck in 60 seconds

posted on 2016-01-21 00:03

This post is a completely copied from @brendangregg from here. Just in shorter and typed by me in hope I can memorize it easier that way, plus a little change with including htop.

Summary: check a linux system for problems immediatly after ssh'ing onto it.

  1. htop - uptime, core diversity, load, swap on first sight via a TUI.
  2. uptime - for load checking, likely unnnecesary after htop
  3. dmesg | tail - check for errors like out of memory
  4. vmstat 1 - check amount of processes (r) and kernel/userland distribution and swap
  5. mpstat -P ALL 1 - check for a single hot core
  6. pidstat 1 - check for high load on single process
  7. iostat -xz 1 - high r/w load? awaits? util%?
  8. free -m - memory available, likely unneded after htop
  9. sar -n DEV 1 - rxkb/s or txkb/s is 125mbytes max for 1G NICs, util% ok?
  10. sar -n TCP,ETCP 1 - act = egress, pasv = ingress traffic, retransmits = bad, usually
  11. top - zxcV and 1 and < and > are your best friends, along with knowing status indices.

Sidenotes:

At 7. buffers = block device caching, cache = page cache for file system.

At 10. just switch columns through the angle brackets keys and have a look the waits (wa) to see if there are disk related issues, after having pressed 1 to show all available cores. d with a number after changes the refresh time to x seconds. In general everything concerning top can be found in the manual.

Lastly, a list of the process states from the mentioned top man page:

D = uninterruptible sleep <<-- waiting for disk
R = running
S = sleeping
T = traced or stopped
Z = zombie

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