Section 5: Troubleshooting

- change control, formal process for managing change
- avoids downtime, confusion, and mistakes
- corporate policy and procedures
- plan for a change
- estimate risk associated with change
- recovery plan if change doen't work
- test before making the change
- document everything and get approval, finally make change

- info gathering, get as many details as possible and duplicate the issue if possible
- identify symptoms, may be more than one sympton
- question users as it is the best source of details
- determine if anything has changed
- approach multiple problems individually
- back up everything
- identify environmental/infrastructure changes
- check OS log files

- theorize what the root cause might be
- Occam's razor: the simplest explanation is often the most likely
- make a list of all possible causes, start with easy theories and the least difficult to test
- research the symptoms

- confirm the theory
- determine next steps to resolve problem
- if theory didn't work, re-establish new theory or call an expert
- if theory works then make a plan

- build the plan, correct issue with minimum of impact
- refer to knowledge base, support articles, or other documentation/manuals
- identify potential effects, have a plan B and a plan C

- fix the issue, implement during change control window
- may need help from a 3rd party

- double check for functionality
- have customer confirm the fix
- implement preventative measures

- build knowledge base
- what did you do, what outcome?
- help desk case notes, searchable database

identify problem >> establish theory >> test theory >> evaluate results >> establish a plan >> implement the plan >> verify full system functionality >> document findings

- Power On Self Test
- test major system components before booting the OS: main systems, video, memory
- failures are usually noted with beeps and/or codes
- know what to do when you hear beep codes based on manufacturers

- blank screen on boot, listen for beeps
- could mean bad video, bad ram, bad CPU, BIOS configuration issue
- check BIOS time and setting, maintained with the motherboard battery, may need to replace battery
- could attempt to boot to incorrect device: set boot order in BIOS configuration, confirm startup device has a valid OS, check for media in a startup device

- Windows Stop Error, blue screen of death
- contains important info, written to event log
- useful when tracking down problems, may need to contact manufacturer support

- startup and shutdown BSOD
- bad hardware, bad drivers, or bad application
- use last known good configuration, run system restore, rollback driver, or safe mode
- reset or remove the hardware if possible
- run hardware diagnostics provided by the manufacturer, BIOS may have hardware diagnostics

- macOS X Spinning Wait Cursor
- spin starts and never stops
- application bug, bad hardware, slow paging to disk
- restart the computer, may be details in the console logs

- is monitor connected?
- check input selection on monitor: HDMI, DVI, VGA, etc
- image may be dim, check brightless controls
- try swapping the monitor or try monitor on another computer
- no video after windows load, use VGA mode (F8)

- no power at the source or from the power supply, try multimeter
- fans spin but no power to other devices, where is fan power connected?
- no POST, bad motherboard?
- case fans may have lower voltage requirements
- check the power supply output

- task manager, check for high CPU utilization and input/output
- windows update, check for latest patches and drivers
- disk space, check for available space and defrag
- laptops may be using power-saving mode, throttles the CPU
- anti-virus and anti-malware to check for bad guys

- heat generation by CPUs, video adapters, and memory
- cooling systems: fans, airflow, and heat sinks help cool down the computer but need to be cleaned
- verify with monitoring software, could be build into the BIOS or try HWMonitor

- electrical problems, always disconnect power immediately
- locate bad components even after the system has cooled down
- replace all damaged components

- no warning and immediate black screen
- may have some details or error message in your event viewer
- heat-related issue: high CPU or graphics, check all fans and heat sinks, BIOS may show fan status and temps
- failing hardware: check device manager, run diagnostics
- could be anything, eliminate whats working to narrow down

- application stops working, may provide an error message and may just disappear
- check the event log
- check the reliability monitor, a history of application problems, checks for resolution
- reinstall the application, contact application support

- computers should hum, not grind
- rattling could mean loose components
- scraping could mean hard drive issues
- clicking could mean fan problems
- pop could mean blown capacitor

- system completely stops, usually not much shown in the event log
- similar to unexpected shutdowns
- check for any activity: hard drive, status lights, try Ctrl-Alt-Del
- update drivers and software patches
- could be caused by low RAM/storage resources
- hardware diagnostics may be helpful

- how far does the boot go before rebooting: BIOS only? OS splash screen?
- bad driver or configuration: F8, "boot from last known working configuration"
- F8 ~ safe mode, if system starts, disable automatic restarts in system properties
- bad hardware: try removing or replacing devices

- bad motherboard battery, often looks like a button
- bad battery will require a BIOS configuration or date/time configuration on every boot
- older systems can reset BIOS configuration by removing the battery
- newer computers use a jumper

- read/write failure, "cannot read from the source disk"
- slow performance, constant LED activity, retry...retry...retry
- loud clicking noise, the click of death, may also include grinding/scraping

- get a backup
- check for loose or damaged cables, overheating, and power supply
- run hard drive diagnostics

- drive not recognized, boot device not found, check lights, beeps, error messages
- OS not found, drive is there but windows is not

- check your cables, physical problem
- check boot sequence in BIOS, check for removable disks, check for disabled storage interfaces
- for new installation, check hardware configuration, check data and power cables, try different SATA interfaces
- try the drive in a different computer

- hard drives will eventually fail
- repairs are difficult and expensive
- SSD may simply stop working, sometimes can read but not write
- data becomes unavailable or corrupted, can be impossible to recover
- always have a backup

missing or faulty RAID controller

each RAID is different, check console before pulling drives

- RAID 0: 2+ disks, single drive failure breaks the array with data loss
- RAID 1: 2+ disks, array will work as long as one drive is operational
- RAID 5: 3+ disks, need all drives operational but one
- RAID 10: 4+ disks, can lose all but one from each set of mirrors

- Self-Monitoring, Analysis, and Reporting Technology
- third party utilities
- avoid hardware failure, look for warning signs
- schedule disk checks, built-in to most drive arrays
- warning signs, replace a drive

- memory access, communication across the bus, spinning drive access, writing and reading data to the storage device
- delays can occur anywhere along the way, need a way to measure storage device access
- IOPS(I/O operations per second), broad metric of maximum performance
- useful for comparing storage devices, hardware: 200 IOPS, SSD: 1,000,000 IOPS

- OS boots normally, other drives not shown, check the BIOS
- internal drives: bad drive or disconnected cable
- external drives: no power to the drive or bad cable connection
- network shares: shared drives can be connected during startup, option to reconnect at sign-in, connected with login script

- check for connected power and signal cable
- input selection on monitor: HDMI, DVI, VGA, etc
- swap monitor or try monitor on another computer
- no video after windows loads, use VGA mode (F8)

- flickering, color patterns incorrect
- check cable pins, especially if missing a color
- distorted image and geometry, check OS refresh rate and resolution settings, make sure display specifications match, check or replace cable
- disable hardware acceleration, troubleshoot with software drivers

- an LCD display is fixed, number of pixels doesn't change
- match a display's native resolution for best video settings
- try using a multiple of native resolution, 2560x1600 is the same as 1920x1200

- some displays will pixel-shift, across all monitors
- LCDs have "image sticking", try to remove by displaying a white screen for an extended period

- always black, manufacturing defect
- usually isn't a problem on your side, not a cable or power issue
- clean the mintor screen with a damp cloth
- replace the monitor, no other option

- check video cable connections
- replace the video cable, usually a quick fix
- try switching display
- confirm display settings in OS, may not match monitor

- too much red, green, blue, yellow, etc
- monitor settings: tint, custom color presets, factory reset
- driver configuration: color tint
- OS configuration: very blue, night light settings

- many monitors include speakers, no sound and/or low volume
- confirm audio input over HDMI, DisplayPort, or Thunderbolt
- check HDMI audio output in the OS
- monitor may support other audio input interfaces, check for audio jacks

- monitor video settings: brightness, contrast
- check the OS: auto-dimming, dim on battery power, driver settings
- backlight failure: some or all of the light, may only be a section of the screen

- large screen projection for conference rooms or large gatherings
- not always LCD, but very common
- metal-halide lamp: very bright/hot light, relatively expensive
- always let bulbs cool, fan will run after shutting off, keep it plugged in
- intermittent project shuts down: no light output, fans may continue to run
- cooling issue: fans constantly cool the bulb, shuts down if temperatures are high
- check airflow, remove blockages, clean dust from air filters

- replacing aging battery
- bad reception, can save battery by going airplane mode
- disable unnecessary features: wifi, bluetooth, GPS
- check application battery usage: settingsattery

- buildup of gas, designed to self contain
- do NOT open the battery packet/container, significant fire risk
- faulty battery, stop using immediately, dispose of properly
- device can be damaged

- backup immediately
- replace screen, no easy fixes
- glass is sharp, screen protectors can help, use clear tape until repaired

- check cables and interfaces, remove any obstructions
- don't use damaged cables, try known-good cable
- verify power adapter, check with a multimeter

- cellular: check signal strength, location matters, outdoor connectivity may be better
- Wi-Fi: limited range, interference can limit throughout, may need a channel/frequency configuration change

- many phones have a LCI(Liquid Contact Indicator), turns color when liquid has been present
- power down phone
- remove case, cards, back, and battery if possible
- bag of rice doesn't actually work well, silica gel is better
- leave phone alone, power off, don't turn it on, don't charge, connect or press any keys, don't heat the phone, don't even move it around
- wait at least a day

- phone will automatically shut down
- charging battery/CPU usage/display light all create heat
- check app usage, some apps use a lot of CPU

- touchscreen completely black or not responding to input
- apple IOS reset, hold down power button and Home|Volume for 10 seconds
- android device restart, remove battery, put back in and power on, or hold down power|volume down until restart

- external interface, charging and data transfer
- not charging?
- not modular, requires a system board replacement

- always a concern
- look for symptoms: unusual apps, large data transfers, pop up messages, high CPU usage, device overheating, excessive battery use
- try a security app or scanner, identify malware infections

- random input or cursor moves without input, common on older screens
- use a touch calibration app, requires user input and touch certain areas of the screen
- system will adjust to the new calibration parameters with no more drift

- print/scan a test page from windows
- use diagnostic tools: web-based utilites built into printer

- lines down the printed page
- inkjet: clean print heads
- laser: check for scratched photosensitive drum
- faded prints, blank pages: lower toner or ink
- double/echo images or speckling: laser printer optical drum not cleaned, ghost from previous drum rotation

- bad printer driver/wrong model
- incorrect page description language(PCL or PostScript?)
- verify printer functionality by printing a test page
- bad application: check the output, upgrade the application

- laser printer output smudges everywhere, toner sticks to everything
- toner not fused to the paper, toner should be permanently melted and pressed, may not be hot
- fuser problem, replace the fuser assembly

- print a letter size page, accidentally send it to a legal size paper tray
- printer stops and shows a message, gives you a chance to fix the issue
- tray selection is provided during the printing process, try printing again, change the defaults in the printer configuration

- careful when removing, don't rip the paper, don't damage internal components
- paper not feeding or misfeeds multiple pages: check the tray, pickup rollers
- creased paper: problems in the paper path, check the paper weight

- corrupted print jobs: print spooler will crash and restart
- problems are logged in windows event viewer and windows-PrintService
- one job may be causing the issue, monitor the queue for details

- output colors aren't same as the display, important for publishing and color printing
- calibrate the monitor, a 3rd party calibration tool will help
- check the paper, white paper is good
- calibrate the printer with proper amount of ink and toner

- something is not operating properly, paper jam or carriage is stalled/jammed
- each printer has a different process, check manuals for removing paper jam
- could be as simple as making sure ink cartridges are installed properly
- may require additional maintenance or replace the printer

- happens after ink or toner has been applied, collate or binding
- staple jams: larger printers will collate and staple groups of paper, each printer manufacturer has a different removal process
- incorrect hole punch location: verify with the printer driver, may require a driver update

- print a portrait page but get a landscape print or vice versa
- check the settings when printing: controlled by the print driver, may require a driver update
- printer has a default setting, check the settings on the printer console

- is there a link light? is it plugged in?
- ping loopback(127.0.0.1), is the protocol stack working?
- ping local IP address, checks local configuration, adapter, and link signal
- ping default gateway, connectivity on the local network
- ping devices on router's outer side, 8.8.8.8 or 9.9.9.9

- interference, something else is using our frequency
- check signal strength: transmitting signal, transmitting antenna, receiving antenna, etc
- incorrect channel: usually automatic, look for manual tuning
- bounce and latency: multipath interference, flat surfaces
- incorrect access point placement: locate close to the users

- predictable: fluorescent lights, microwave ovens, cordless telephones, high-power sources
- unpredictable: multi-tenant building
- measurements: SNR(signal to noise ratio), performance monitor

- Signal, what you want
- Noise, what you don't want: interference from other networks and devices
- Ratio, you want a large ratio, 1:1 is bad

- windows alert in the system tray: "limited or no connectivity" or "no internet access"
- check the local IP address, an APIPA address will only have local connectivity
- if DHCP address is obtained, perform the ping tests

- most real-time media is sensitive to delay, voice communication or live video
- if you miss a packet, there's no retransmission
- jitter is the time between frames, excessive jitter can cause you to miss information, choppy voice calls

- high speed and low latency
- check the internet connection
- verify the local netowrking equipment, old router can cause significant problems
- view the network performance, a packet capture would be useful

- a delay between the request and response, waiting time
- examine the response times at every step along the way, may require multiple measurement tools
- packet captures can provide detailed analysis, microsecond granularity, get captures from both sides

- network interface goes up and down, over and over again
- verify the cable, check wiring
- move between switch interfaces, is the flapping associated with the switch interface or the device?
- replace bad hardware or cables, may require additional purchases