What does the lightning bolt mean?
There is a lightning bolt icon flashing on the top right of my screen. What does it mean?
Here's a picture:
That's the new undervoltage symbol. Your Pi's power supply is marginal or insufficient for its requirements.
From the raspberrypi.org blog page:
Finally on the subject of icons, in the past if your Pi was working particularly hard, you might have noticed some yellow and red squares appearing in the top-right corner of the screen, which were indications of overtemperature or undervoltage. These have now been replaced with some new symbols that make it a bit more obvious what’s actually happening; there’s a lightning bolt for undervoltage, and a thermometer for overtemperature.
Official doc for the icons: https://www.raspberrypi.org/documentation/configuration/warning-icons.md And a video explaining it: https://www.youtube.com/watch?v=JadID7eRTtQ
The lightning bolt means that the Pi is not receiving the required voltage. This may be due to the power supply you are using or the cable (if seperate). You should switch to a better supply/cable as undervolting can lead to SD card corruption and other difficult to trace issues.
You don't mention what model Pi you ae using and what if anything you have plugged into the USB ports but you may be able to get by with your existing powersupply/cable if you use a powered USB hub to connect any USB device.
The lightning bolt means that you don't have enough power going to the Raspberry Pi.
Almost any standard micro USB cable will be able to power the Pi. Most of us have one or two laying around from getting them for our phones and we could easily use what we have to charge our phones to power the RPi.
However, the Raspberry Pi should have a 5 volt 2 amp USB power cable to sufficently power the the device (and not get the bolt).
Most Android/Smartphone/USB chargers though run on a 5 volt 1 amp charger, and some of the "fast chargers" are only 5 volt and less than 2 amp. These are big generalities and are constantly changing and do vary depending on how cheap you got it and where from and for what purpose.
Some of those "fast chargers" can go for up to $30, and will be a 5 volt 2 amp charger. However, you can get one from adafruit.com for just about $8, which is what a regular phone charger would cost elsewhere, see 5V 2.4A Switching Power Supply w/ 20AWG 6' MicroUSB Cable.
This amount of power, might be too much for your computing needs for the Pi. So a standard 5 volt 1 amp charger might be good enough until you decide what you are doing with it or just while you are learning and goofing with the OS and such.
I bought a 5 V 2.1 A from somewhere and it works great for my Pi, similar to the one from Adafruit.com. I forget where I got it though.
If you want some upvotes, you should edit your answer... Surely you mean 5V 1A, and 5V 2A?
It also appears if you power the Pi from the GPIO power pins.
Everything works fine but the power led will not be lit.
**Do you have a reference for this, or is it an inference?** If the later, then perhaps what it really means is you are supplying insufficient voltage via the GPIO pins. Note that the lightning bolt and the PWR led being off are just warnings. They do not not necessarily indicate anything won't work, but it might be a clue if, e.g., you suddenly drew a lot of current via the USB jacks and the pi "mysteriously" rebooted.
References? I, also, will upvote your answer - _if_ you can ameliorate your answer, and provide (substantially) more information...
In my experience, powering the Pi via GPIO can lead to serious problems if the CPU is very busy and/or USB ports suck a lot of power. We had a case where the network interfaces continuously restarted making it impossible to reach the Pi via SSH.
According to the schematic (pi v3) the +5V from the USB is attached to the +5V internal rail via a resettable fuse. So you can provide equivalent supply via the 5v header as long as you provide similar over current protection.
He is right. I just pluged a mini fan in GPIO 4-5 pins and that bolt appeared on top right of screen and power led (red) turned off, blinking randomly once in 5-10 seconds. I pulled back fan connection and restarted Pi(3B+) and everything was okay. I am supplying 5V3A via mini USB port.