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One of the quickest-to-use tools for a picture of the current state of a Linux system is top which displays current top processes running, system uptime, load average, CPU utilization, memory usage (real and swap), and other items.


For a quick view of the system uptime and load averages, run uptime .


iostat displays information about the current state of the disk I/O on the system


To see what network ports are currently open and listening, use netstat . For example, netstat -an | grep 80 will display what is using port 80 (and 8080, and anything else that has '80' in its port number).


lsof will show what process is holding open a network port or file. To use "list open files" to see what process is holding port 80, run lsof -i:80


To see a list of the process table, run ps . My favorite argument sequence is aux which gives lots of information back: ps aux

The similar call on a Solaris machine is: ps -ef


For a fuller diagnosis of what a given process is doing, strace can be a lifesaver. It essentially wraps around the process in question (either by running strace<program-name> , or by attaching to a running process with strace -p<pid>

On Solaris, the similar tool is truss .


The GNU debugger, gdb , is a massively-useful tool in the right hands: tracking individual calls inside a program, setting breakpoints, etc: it should be learned by every developer, and known to advanced users.

User error

"User error" is among the most commonly-cited errors with software and systems: the operator did something the creators did not expect. To use a ubiquitous car analogy, it's "user error" if the driver hits the gas instead of the brake. One interesting article makes the claim that there is [almost] no such thing as "user error", and that instead it should be the developers who make tools not resilient enough to handle any user (no, a car manufacturer can't make the gas act like the brake when you "meant to stop", but maybe software developers can make their products less error-prone, or at least have them give better errors when they do have a problem).

    A spectrum of user-initiated errors:

  • Typos (misspellings, fat-fingering, generally mistyping something)
  • External environmental problems (eg unplugging a network cable)
  • Clickos (ie, misclicks - akin to mistyping)
  • Forgetfulness
  • Etc
From personal observation, I would guess user error accounts for 70-80% of all errors seen.

Post-mortem data collection

When something has gone so awry that it has violently crashed, or even taken out its host system, it's time for some post-mortem data collection - maybe even forensic analysis.

Core dumps, log files, and even images of whole drives can be investigated during a post-mortem analysis of problems seen: as your technical acumen grows, you'll be able to investigate more parts of these prior to escalating to the tool's support or development teams.

Pro-active, preventative measures

Ideally, we would all live and work in a world where nothing ever failed, and everyone acted the way they are "supposed" to. Sadly, that world does not exist. So what can we do to help prevent issues in the first place, or respond more adeptly when they [inevitably] occur?

Some solutions are simple: add more memory to the system; increase swap space; verify storage quotas; make sure all the resources I need are available; etc. Many can be more complex.

If there is a set of "Known Issues" or release notes that come with a particular product, make sure you read and are aware of them: there is almost nothing more frustrating than finding out there is a known issue, but you didn't check the manuals first!

Asking "why"

If you're on the administrative side of the technical world, and not just the end-user side, the other big thing to remember is to always ask "why". Why did it fail? Why did we miss the known issue? Why were we not notified a necessary resource was going to be down? Why was there no alert sent about resources nearing their limits? If you can ask (and answer) those, then you should be able to reduce the number of "why" questions you need to ask in the future - because hopefully you're solving problems before they arise.

"future-proofing" - is it possible?

The idea of "Future-Proofing" is to create an environment that can survive future developments without needing to be changed itself. A common example of this would be to look at the current and expected growth needs of the email infrastructure of an organization, and then size the mail servers to handle 15-25% more than the expected growth (ie 100 users today, adding 20% per year, size the environment today for 200 users in three years (173 expected, plus ~15%). Or it could mean ensuring that data you are working with today in version 4.3 of some tool will be accessible when upgrading to 7.2 in 4 years.

When relying on external vendors, guaranteeing your environment is future-proof may not be possible - they could decide to change database schemas, file formats, etc. Likewise, when relying on expected growth patterns, you may exceed those expectations (requiring additional licenses, hardware, etc), or you may not meet those plans, and have an unnecessarily oversized environment. Several mitigating strategies exist for these eventualities, but are beyond the scope of this lesson.

Closing thoughts

You've completed this module, and so now you're ready to troubleshoot the most ornery problems in the most obscure corners of your system, right? Don't let me discourage you from that lofty goal: but the reality is that becoming a good troubleshooter takes time, practice, lots of exposure, practice, skimming skills, practice, and patience. Oh, and did I mention: practice!

Lots of professions require troubleshooting skills, and each has their own tricks and tips to follow: auto mechanics will check the OBDII and listen to a rattle; electricians look for wiring faults; doctors look at symptoms to come up with a diagnosis. Skills learned in one field may not always translate into another, but if you can learn the basics (which DO all transfer), then gleaning insights from others can only improve your own personal Bag O' Hatchets.

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Berger describes sociologists as concerned with
Mueller Reply
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Source:  OpenStax, Debugging and supporting software systems. OpenStax CNX. Aug 29, 2011 Download for free at http://cnx.org/content/col11350/1.2
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