Red Hat Enterprise Linux Troubleshooting Guide

Identify, trap and get to the bottom of universal concerns confronted via crimson Hat company Linux directors utilizing most sensible practices and complicated troubleshooting techniques

About This Book

  • Develop a robust figuring out of the bottom instruments to be had inside of crimson Hat company Linux (RHEL) and the way to make use of those instruments to troubleshoot and get to the bottom of real-world issues
  • Gain hidden guidance and methods that can assist you quick notice the cause of terrible network/storage performance
  • Troubleshoot your RHEL to isolate difficulties utilizing this example-oriented consultant choked with real-world solutions

Who This ebook Is For

If you will have a uncomplicated wisdom of Linux from management or advisor adventure and want so as to add on your pink Hat company Linux troubleshooting talents, then this booklet is perfect for you. the power to navigate and use uncomplicated Linux instructions is expected.

What you are going to Learn

  • Identify concerns that want fast solution opposed to long-term root reason analysis
  • Discover instructions for trying out community connectivity similar to telnet, netstat, ping, ip and curl
  • Spot functionality matters with instructions corresponding to most sensible, playstation , loose, iostat, and vmstat
  • Use tcpdump for site visitors analysis
  • Repair a degraded dossier approach and rebuild a software program raid
  • Identify and troubleshoot concerns utilizing dmesg
  • Troubleshoot customized purposes with strace and data of Linux source limitations

In Detail

Red Hat company Linux is an working procedure so that it will modernize your infrastructure, enhance potency via virtualization, and eventually organize your info heart for an open, hybrid cloud IT structure. It offers the steadiness to tackle modern demanding situations and the flexibleness to evolve to tomorrow's demands.

In this e-book, you start with basic troubleshooting most sensible practices and get an summary of the Linux instructions used for troubleshooting. The e-book will hide the troubleshooting tools for internet functions and companies similar to Apache and MySQL. Then, you are going to learn how to determine process functionality bottlenecks and troubleshoot community matters; all whereas studying approximately very important troubleshooting steps comparable to knowing the matter assertion, constructing a speculation, and realizing trial, blunders, and documentation. subsequent, the publication will aid you trap and study community site visitors, use complex process troubleshooting instruments comparable to strace, tcpdump & dmesg, and detect universal matters with method defaults.

Finally, the publication will take you thru a close root reason research of an unforeseen reboot the place you are going to learn how to get well a downed system.

Style and approach

This is an easy-to-follow consultant jam-packed with examples of real-world middle Linux techniques. all of the issues are offered intimately when you are acting the particular troubleshooting steps.

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31 zero. 00 forty eight. 12 machine: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz watch for r_await w_await svctm %util sda zero. 70 zero. eighty 804. forty nine 776. eighty five 79041. 12 76999. 20 197. 35 sixty four. 26 forty-one. forty-one zero. fifty four eighty three. seventy three zero. forty two sixty six. 38 dm-0 zero. 00 zero. 00 zero. ninety zero. eighty three. fifty nine three. 19 eight. 00 zero. 08 50. 00 zero. 00 106. 25 19. 00 three. 22 dm-1 zero. 00 zero. 00 804. 29 726. 35 79037. fifty two 76893. eighty one 203. seventy five sixty four. sixty eight forty three. 03 zero. fifty three ninety. 08 zero. forty four sixty six. seventy five avg-cpu: %user %nice %system %iowait %steal %idle five. 22 zero. 00 eleven. 21 36. 21 zero. 00 forty seven. 36 equipment: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz wait for r_await w_await svctm %util sda 1. 10 zero. 30 749. forty 429. 70 84589. 20 43619. eighty 217. forty seven seventy six. 31 sixty six. forty nine zero. forty three 181. sixty nine zero. fifty eight sixty eight. 32 dm-0 zero. 00 zero. 00 1. 30 zero. 10 five. 20 zero. forty eight. 00 zero. 00 2. 21 1. 00 18. 00 1. forty three zero. 20 dm-1 zero. 00 zero. 00 749. 00 391. 20 84558. forty 41891. eighty 221. eighty seventy six. eighty five sixty nine. 23 zero. forty three two hundred. ninety five zero. 60 sixty eight. ninety seven From the output of iostat, we will be able to verify the next: The CPU of the program is presently spending quite a lot of time looking ahead to I/O, 30%–40% it seems that the dm-1 and sda units are the most-utilized units From iostat, it seems that those units are at sixty eight% usage, a bunch that turns out is kind of excessive at the foundation of those info issues, we will be able to establish that there's a strength I/O usage factor, until sixty eight% usage is predicted. utilizing iotop to figure out which techniques are eating disk bandwidth Now that we've got decided huge volume of CPU time is being spent awaiting I/O, we should always now specialize in what techniques are using disks the main. to do that, we'll use the iotop command. # iotop overall DISK learn : a hundred. sixty four M/s | overall DISK WRITE : 23. ninety one M/s genuine DISK learn: a hundred. sixty seven M/s | real DISK WRITE: 38. 04 M/s TID PRIO person DISK learn DISK WRITE SWAPIN IO> COMMAND 19358 be/4 root zero. 00 B/s zero. 00 B/s zero. 00 % forty. 38 % [kworker/u4:1] 20262 be/4 root a hundred. 35 M/s 23. ninety one M/s zero. 00 % 33. sixty five % bonnie++ -n zero -u zero -r 239 -s 478 -f -b -d /tmp 363 be/4 root zero. 00 B/s zero. 00 B/s zero. 00 % 2. fifty one % [xfsaild/dm-1] 32 be/4 root zero. 00 B/s zero. 00 B/s zero. 00 % 1. seventy four % [kswapd0] From the iotop command, we will see that approach 20262, that's working the bonnie++ command, has a excessive usage in addition to huge disk learn and write values. From iotop, we will ensure the next: The system's overall disk reads in line with moment is a hundred. sixty four MBps The system's overall disk writes in step with moment is 23. ninety one MBps method 20262 working the bonnie++ command is studying a hundred. 35 MBps and writing 23. ninety one MBps evaluating the totals, we discover that technique 20262 is almost all contributor of disk reads and writes Given the above, it appears we are going to have to determine additional info approximately procedure 20262. utilizing playstation to appreciate extra approximately procedures Now that we've got pointed out a method that's utilizing an important quantity of I/O, we will examine the main points of this technique with the playstation command. we are going to once more use the playstation command with the --forest flag to teach the father or mother and baby strategy courting. # playstation -elf --forest 1007 zero eighty zero - 32881 poll_s Feb08 ? 00:00:00 \_ sshd: vagrant [priv] five S vagrant 11242 11239 zero eighty zero - 32881 poll_s Feb08 ?

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