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PoE (Power over Ethernet)

NO, NO, NO!!! Absolutely not!!! Very dumb idea!!! If used to transport power (or phone signals, a setup I fixed at one location), those "unused pairs" will induce noise into the signal pairs (two of 'em, coming and going) and the result will be a lot of packet errors. Whomever thought up this idea is a blithering idiot! Are they that hard up for cable that they have to usurp pairs for non-network purposes? Besides, there are instances where the unused pairs are internally grounded in some network gear. Put voltage to that and something's gonna go up in smoke. At the risk of being repetitious, really lame idea!

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Unix and Linux Troubleshooting E-Book  
- My Unix and Linux Troubleshooting E-Book is ready to go -

Power failures and IP addresses  
- Why should a power failure have reset ip addresses? That printer definitely has a static address; so did the server. -

Dial-up and Broadband  
- dial-up Earthlink with Verizon Broadband. Back when DSL was all the rage, we'd have to put DSL filters on any modem or fax lines -

- Verizon said that they'd have the same IP, and the same type of T1, so all they had to do was unplug their router(s), move them, replug and all would be fine.. -

It's OK to use your brain when I'm talking to you  
- Customer called saying that program foobar32 would not run, complaining of missing library foolib32.so. Given the naming of the library, I suggested that foobar32 probably needed to be reinstalled and she agreed. -

A Golf Cart is not a Computer   2015/03/29 anonymous
- You can't let batteries discharge over the winter, so when it got cold I moved it out back near an electrical outlet where I could plug the charger in. -

Installation and light training Boston and New England  
- Computer hardware and software installation service -experienced, punctual, reliable -

SCO Compiling error  
- On an hp Netserver Lc3 server (SCO 5.0.5) I'm trying to reconfigure the backup device using "mkdev tape" but at the end of the wizard I'm returned the following "recompiling kernel error" -

Accidental lockout  
- I'm beginning to really hate the old SCO systems that are left out there. However, when they call with a problem, I have to help, right? -

Wrong DNS causes interesting glitch  
- An incorrect old DNS server in /etc/resolv.conf causes interesting behavior -

Strange Linux Tar problem  
- Tar run from inittab script produces corrupt files, but cpio does not. What on earth is causing this? -

A Change of Address  
- The caller had a downed Unix machine. Big crash, dead hardware, but he had a backup machine that he had restored backups to and had changed the IP to match the old server -

I can't get to the Internet!  
- You can't trust what people say, because their ability to describe a problem accurately depends upon their general understanding of technology. -

Router down  
- Network down and then again.. and again.. Normally I don't like to see WiFi in a business environment, and if it must be there, I like to see it locked down very securely: -

Lazy DNS  
- I had a call this morning from a customer who wanted me to come down because their mail server was broken. They had experienced an ISP outage, which subsequently was fixed, but their mail server wasn't getting anything still. I was actually ready to go out the door when I thought to just double check reality, and that check kept me sitting right here: -

Invalidating the Linux buffer cache   2012/08/01 SimonL
- How to actually test the disk drive to know that data really has gotten to the disk drive. This could be because you want to test the performance of the drive, but could also be when you suspect a drive is malfunctioning: if you just write and read back, you'll be reading from cache, not from actual disk platters. -

Phantom Connections  
- Mysterious typing: I had coffee with Mark Jones of Micronet Network Services, Inc this morning. The purpose was to discuss some Unix and Linux customers he has, but of course we started swapping stories and I liked this one so much I had to share it with you -

Mysterious lockups  
- Dead in the water hangs are the most annoying; There's no crash, no panic: everything just stops dead. -

Plastering your printer  
- Back in the computer room again. I looked at the printer, it was fairly new: in fact I had installed it not very long ago. It certainly didn't have a worn out feed mechanism and obviously it had just printed several pages. As I thought about that, I became aware that the room seemed humid - much more so than it should have been given the temperature. I then noticed the elephant: a freshly plastered wall. I put my hand on it, it wasn't damp, but it was still fairly cold. The manager had followed me. I turned and asked the obvious: "Was this done recently?". She responded affirmatively. -

Troubleshooting Mistakes  
- The very first part of troubleshooting is identifying the problem. That's not always easy even for skilled professionals. -

Debugging a network failure  
- A heat wave can cause electrical problems: This morning I had a call from a Boston customer. "Everything's down", he said, "Internet and our servers. We can't get to anything. But.. the guys who came in early are still working." -

Legacy ISA  
- I found a professed "competent" student at the local university who spent a couple of hours destroying the setup in one of the machines. We now have one machine working.. -

Geek Wiring  
- Our phones went dead yesterday. That has caused us to be very ticked off at Comcast because we've been without service a lot. -

Net:FTP $ftp->put problem!  
- using ftp->put to upload file to ftp server: I am using $ftp->put to upload file to ftp server but it is not working... -

Apache and PHP killed by thttpd  
- OK, I thought, let's kill off all the current httpd processes and start up manually. Maybe that would give us a clue. I asked him to run "killall httpd" -

Maximun number of socket connections  
- 100 connections hangs server.. configuration? Possible tuning limits on SCO Unix that might cause this. -

New Dell machine kills server  
- A new machine kills an old server (network problem). Her email said the machine was getting an ip address, but just wasn't accessing network resources. -

The Art of Troubleshooting  
- Yes, troubleshooting is an art!. The key points to mastering this art is knowing the system in and out, using the right tools and, of course, googling. -

SCO unixware 2.1.3  
- ftp from win 98 m/c to SCO unixware 2.1.3 server: when iam doing ftp from win 98 m/c to SCO unixware 2.1.3 server, server network card stop responding it doesn't ping.finally i have to restart the server,then network card start working. -

Print copies problem  
- multiple copies with lpr: When attempt to remote print several copies of a document with the command 'lp -n2 -d printer file', leaves printed one copies. -

When all other explanations fail..  
- Creative thinkers don't react to problem solutions with 'That's impossible!'. We construct theories as to the cause of our observed problem. -

C Pointer Problems   2011/04/18 TonyLawrence
- If a program works under a debugger but crashes otherwise, the problem is almost always an uninitialized pointer. -

Troubleshooting Skills  
- For at least some of the people asking 'dumb' questions, they may have little choice, or rather this may be their deliberate choice because they know from bitter experience that they can't do much better no matter how they try. -

Tape Errors - Openserver 5.0.7  
- Having trouble with an IDE tape drive - Dell Powervault 100T (Travan 20/40 Gb drive). -

cache data corruption   2012/02/12 TonyLawrence
- The symptoms were occasional data corruption but only in frequently used files. All the usual suspects were hauled out and examined; everything passed muster. -

2038 time overflow  
- Sheesh, you think so? No, it's not "may": if current Unix and Linux OSes are still running in 2038, yes, they WILL overflow their time counters. -

PoE (Power over Ethernet)  
- Isn't this just looking for trouble? Won't this induce noise -

Email and Phone Support  
- I am not doing as much SCO or Linux support as I used to. However, I used to do a LOT of SCO work. I MAY be able to help with some Unix/Linux things. Please send email first, describing your needs -

Email and Phone Support  
- If you are a consultant or MIS manager and primarily support Windows but need Unix or Linux help now and then, one of the phone or email support options may be just what you need. -

g++ not working  
- How not to ask a technical question - hint: you need to say a little more than 'it doesn't work'. -

Simplified SCO_OSR5 Printing  
- Although this article strongly references SCO Unix printing, the background and trouble-shooting tips are valuable on any Unix/Linux platform. -

Troubleshooting: Preserve the scene  
- You've seen it on television or in the movies: important evidence is lost at a crime scene because someone wasn't careful enough to preserve it. Computer troubleshooting is no different. -

Troubleshooting: Try something different  
- I'm also full of horse manure. To this day, I have no idea why that server was causing everything to reboot. I have no idea why I yelled at the three Mac experts (as it turned out, all three were Mac consultants) to shut that server down. -

Interesting thread (ls vs. ls -l) - lessons for newsgroups  
- ls vs. ls -l - Why did "ls" work but "ls -l" hung and froze? There are a lot of bad guesses and poor troubleshooting techniques to be seen in the thread. -

Dead Rat fixes computer problem  
- This is a story of how a dead rat solved a problem. I still don't know what the problem is, but, thanks to a dead rat or two, I do know what the problem isn't. -

Mac OS X Power Hound  
- 0ob Griffiths is the creator of Macosxhints.com and you could describe this book as a loosely organized version of the better hints and tips you'll find there. -

Linux|Unix Trace Toolkit: Tech Words the Day  
- Sometimes you want to trace a specific process, and strace does that nicely. But other times you want to see more about the whole system; that's LTT. -

strace, trace: Tech Words the Day  
- System Call Trace, strace on Linux, often just trace on other Unixes. I have used this tool many times to track down baffling application problems. For example, I recently had a client transfer Cobol programs from an old SCO system to Linux. -

Debugging Facetwin Remote Printing Connections  
- I got a call today from one of my customers complaining that their remote printer was no longer printing. 'What changed?', I asked. 'Nothing at all!', she replied in her charming southern drawl, 'It just stopped printing!'. -

Setting up a new firewall  
- I double checked my work, didn't see anything wrong. Checked it again, power cycled this hardware and the DSL device. Still couldn't ping the gateway. -

LOD Communications, Inc.
- Computers screw up. You can have meaningless instructions, attempts to divide by zero, attempts to access non-existent memory, and more. -

I don't know Unix   2012/06/15 TonyLawrence
- When people say 'I don't know Unix (or Linux), what they really mean is usually 'I don't know much about computing, period'. -

Bootable Utility CD  
- There are many useful tools on this CD, to help you solve just about any PC problem -

- It's also handy while writing code: stash samples from data files or read in code you want to cut and paste from. -

Open Source Network Administration  
- Many tools for monitoring, and troubleshooting networks are included; Sysmon, Oak, Neo, MRTG, tcpdump, netstat, traceroute, etc.. are all covered. -

SCO's custom problems  
- SCO's custom is amazingly bad software. "Unable to start software manager. Possibly because it is already in use" -

- That's a boot after powering the machine off as opposed to just rebooting. It's not a 'power cycle' (just shutting the poor thing off because it is unresponsive and then immediately back on). -

clfree panic and no logins at console  
- All serial printers suddenly stopped workingand a 'PANIC: clfree - Free block ' message appeared on the console screen. They power cycled; system 'went dead' after the fsck - no logins. -

- List Open Files. This is much more than it sounds like. It is similar to 'fuser', but has much more power. I often use it to find processes using specific network ports -

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