Categories
Network Technologies

How to force snmpwalk to convert strings to numeric OIDs

Intro

It’s a little hard to find this information on the Internet, so I’m amplifying the correct answer here by using my blog.

The details

I’m not super-competent with MIBs and such, but I manage for my purposes with my basic understanding. I have access to an F5 bigip with various IPSEC tunnels on it. I want to use Zabbix to check the status of those tunnels. So I do an SMPwalk like this:

snmpwalk -v3 … -c public 127.0.0.1 F5-BIGIP-SYSTEM-MIB::sysIpsecSpdStatTunnelState

which produces output like this line:

F5-BIGIP-SYSTEM-MIB::sysIpsecSpdStatTunnelState.”/Common/tunnel-01″.58401 = STRING: up

But I cannot take that as it is and use it in an snmpget like this:

snmpget -v3 … -c public 127.0.0.1 F5-BIGIP-SYSTEM-MIB::sysIpsecSpdStatTunnelState.”/Common/tunnel-01″.58401

That produces an error like this:

Unknown Object Identifier (Index out of range: /Common/tunnel-01 (sysIpsecSpdStatTrafficSelectorName))

So we need to convert the string into a numeric OID. But how?

The answer

Use the -On switch as an additional argument in your snmpwalk.

You will get a scary long OID, but it will at least be numeric.

Gonig further

You can then deconstruct the response and reconstitute the section at the beginning with a nice name. For my F5 example

.1.3.6.1.4.1.3375.2.1.2.17.1.3.1.14

becomes

F5-BIGIP-SYSTEM-MIB::sysIpsecSpdStatBytes

I think. Then preserve the following digits as is.

Conclusion

We have shown how to output a numeric OID from an snmpwalk. This, specifically, is sueful in converting a string embedded in the output into a numeric OID, which may then be used by other SNMP applications such as Zabbix which may or may not have the MIB file loaded. The secret is simply to use the -On switch in snmpwalk.

References and related

My Zabbix FAQ – questions you wish they had answered, can be very helpful

Categories
Admin Network Technologies TCP/IP

Verizon Airspeed Hotspot uses ipv6 and interferes with VPN client Global Protect

Intro

The headline says it all. I got my shiny brand new Verizon hotspot from Walmart. I managed to activate it and add it to my Verizon account (not super easy, but after a few stumbles it did work.) I tried it out my home PC – works fine. I tried it out on my work PC. No good. My Global Protect connection was unstable. It connects for about a minute, then disconnects, then connects, etc. Basically unusable.

The details

I have heard of possible problem with the GP client (version 5.2.11) and IPv6. So I looked to see if this hotspot could be handing out IPv6 info. Yes. It is. But is that really making a difference? I concocted a simple test. I disabled IPv6 on my Wi-Fi adapter, then re-tested the GP client. The connection was smooth as glass! No disconnects!

Disable ipv6 on your Wi-Fi adapter

Bring up a powershell as administrator. Then:

get-netadapterbinding -componentid ms_tcpip6

will show you the current state of ipv6 on your adapters.

disable-netadapterbinding -Name “Wi-Fi” -ComponentID ms_tcpip6

will disable ipv6 on your Wi-Fi. And

enable-netadapterbinding -Name “Wi-Fi” -ComponentID ms_tcpip6

will re-enable it.

ipconfig /all output

For the record, here are some interesting bits from running ipconfig /all:

Wireless LAN adapter Wi-Fi:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) Dual Band Wireless-AC 8265
Physical Address. . . . . . . . . : 0C-BD-94-98-11-5B
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Temporary IPv6 Address. . . . . . : 2600:1001:b004:2b78:8ab:145c:d014:2edd(Deprecated)
IPv6 Address. . . . . . . . . . . : 2600:1001:b004:2b78:2cc0:71b0:7f1e:a973(Deprecated)
Link-local IPv6 Address . . . . . : fe80::2cc0:71b0:7f1e:a973%30(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.103(Preferred)

Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Thursday, April 21, 2022 4:54:04 PM
Lease Expires . . . . . . . . . . : Friday, April 22, 2022 4:54:04 AM
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DHCPv6 IAID . . . . . . . . . . . : 302832932
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-28-89-F6-8E-B0-5C-DA-E6-09-0A
DNS Servers . . . . . . . . . . . : fe80::50ae:caff:fea8:1dbc%30
192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled

But, having done all that, I can only occasionally connect to GP. It seems to work slightly better at night. ipv6 does not seem to be the sole hiccup. No idea what the recipe for reliable success is. If I ever learn it I will publish it. Meanwhile, my phone’s hotspot, also VErizon, also handing out ipv6 info, usually permits me to connect to GP. It’s hard to see the difference.

Conclusion

The Verizon Airspeed Hotspot sends out a mix of IPv6 and IPv4 info to dhcp clients. Palo Alto Networks’ Global Protect client does not play well with that setup and wil not have a stable connection.

I do not think there is a way to disable IPv6 on the hotspot. However, for those with admin access it can be disabled on a Windows PC. And then GP will work just fine. Or not.

Oh, and by the way, otherwise the Airspeed works well and is an adequate solution where you need a good reliable hotspot. Well, in fact, don’t expect reliability like you have from a wired connection. After a couple hours, all users just got dropped for no apparent reason whatsoever.

Categories
Consumer Tech

Consumer Tech: Setting up an Echo Dot while staying at a hotel

Intro

I’m sure many people have faced this. You like to query your Echo Dot for basic information and you’d like to take it with you and work in your hotel room so you can get the local weather, etc. But then you are foiled by the setup process until you finally give up after trying to discover it as a new device numerous times.

I was in that exact situation last week. Finally I thought of something that broke me out of the discover device loop, so I wanted to share that.

The details

A hotel will typically offer Internet, but through a “captive portal.” This means, technically, the password they provide you at the front desk is not the SSID password, but a password to their portal’s web site. So it is technically not part of the WiFi information. That’s what makes it so hard for dumb devices like the Echo Dot to get past that page.

Normally you go to your room after checking in, and you perhaps set your phone to use their WiFi after dutifully logging in to the portal page. Then you get around to setting up your Echo device. I could not manage to finish the Echo Dot configuration under those conditions last week, though I tried many times over, including manual setup.

What I realized, though, is that it might help to start clean. So I “forgot” the hotel’s SSID (WiFi) on my phone. Then I was only using 4G communication. Then I went through the Device Setup in the Alexa App on my phone. At some point you get asked which WiFi to connect to, and you get redirected to the captive portal, where you put in the information. In other words I stumbled my way through it. But then it did work.

So I’d say the upshot is to configure the Echo Dot first before setting up your phone to use the hotel’s WiFi. I’m not sure it will always work, but at least it did work once! But if you did things in the wrong order go to your WiFi settings and “forget” the hotel’s WiFi – it may have the same effect.

2nd test – successful

Since I’m supposed to be the expert I had the opportunity to try my own technique at another hotel. It was about 10 minutes of stumbling, but then it did work in the end. Maybe my tip helped, maybe not.

As I do not have the straight recipe, you have to be willing to try different things. Pay special attention to whether or not your setup device is connected to the Dot’s WiFi (amazon-dkd or something like that) or not. That’s generally a good thing. Then you have it (the Dot) search for available WiFi networks. I guess. It’s confusing. You’ll probably need to put your Dot into setup mode mulitple times. Esimated time to stumble your way through it: 10 minutes. You can decide if it’s worth it or not.

Other ways

I’m thinking about mac address emulation, i.e., temporarily emulate the MAC address of the Echo device with a more amenable device, and do the poral login. But I haven’t had time to research it. I will post it here if I ever figure that out.

Categories
Linux

Install WSL2 for Windows 10 Home Edition: not as easy as they say, but not impossible either, and definitely worth it

Intro

I installed WSL2 on my work laptop a couple weeks ago. It didn’t go terribly smoothly but now that I have it, I love it. I had been using a Cygwin environment, but I fear that is looking a little long in the tooth. WSL2 is fast to start up. But the main contrast is that while Cygwin is an emulator, WSL2 is a true hypervisor so you get a full-fledged linux VM, right on your PC. Of course this was always possible with products like VirtualBox or whatnot, but Microsoft has sort of built in this capability with newer versions of Windows 10, so there’s no mussing with external software any longer.

But at work I have Windows 10 Professional, of course. What about at home where I have Windows 10 Home Edition like most of us? My understanding is that you could not run a hypervisor with Windows 10 Home Edition. And I was probably right, until recently. But now you can. I know because I just managed it tonight.

None of the tutorials out there were exactly right, but they all contained pieces of the truth. So my contribution is to add weight to the correct steps you’ll need to take. Unfortunately I only get to do it once so my notes aren’t the best. Still, I may be able to spare you some pitfalls.

Why you should want WSL2

If you love linux command-line, then I would say this is a must-have.

What doesn’t work

You’ll see suggestions to fire up powershell and simply run

wsl –install

Chances are about 95% that that won’t work if you are reading this article – would that it would be so simple.

Instead, do this

Open a powershell window as administrator. To do that type powershell in the start menu, and look around at all the options. Pick out the one that mentions Run as administrator.

Running Powershell as Administrator

Then enter this command into the PS window.

dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart

Then this.

dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart

Then this.

wsl --set-default-version 2

You need to update your kernel. Download this WSL2 kernel update file and install it: https://wslstorestorage.blob.core.windows.net/wslblob/wsl_update_x64.msi

A reboot at this point is probably a good idea.

Now you need to get yourself a linux distro to install.

There are certain wsl commands you can issue which will helpfully give you the URL to the Debian distro: You put the URL into the browser and it redirects you to the MS Store. But I forget what that is. perhaps wsl -d Debian. But I suppose you can simply go to the MS Store directly and search for Debian and install it.

Enhance your experience with Windows Terminal

One good suggestion out of Windows Central is to use Windows Terminal. At least it looks good. I haven’t had time to try it myself. I normally just fire up a CMD window and type wsl. My Debian starts immediately and I have a satisfactory command-line environment. But working with multiple windows will be nice so I have to check it out.

Just look for Windows Terminal in the MS Store.

Windows Central suggestions

A web site called Windows Central has a pretty good stepwise guide. But their advertising is so obnoxious, I’m afraid to accidentally touch any part of the page for fear of getting sent to one of their many advertisers. Even still it probably happened about five times. So I won’t make the link to them too prominent. And, anyway, their guide is a little oversimplified.

My equipment

I have a four-year old HP Pavilion laptop running Windows 10 2021 H2 if I remember correctly. It has solid state drives so it’s not too slow, and it boots pretty quickly.

BIOS – basically impossible to get into these days

I’m sure people who do this for a living will disagree, but for ordinary people it’s basically impossible to disrupt the boot process to modify the BIOS settings. And you may need to do that. In fact that was the hardest thing of all for me. Pressing F10 or delete or Escape or F2 – and does that mean hold the FN key down first?? No one explains that, and I don’t have patience to watch a YouTube video. But after trying a bunch of combinations and booting a bunch of times, and never getting into the BIOS settings, I was really glad to learn Windows 10 offers an alternate way! And it works…

Access BIOS settings from Windows 10

Very briefly, the steps are:

Windows Settings > Update & Security > Recovery > Restart Now > Advanced Startup -> Restart Now > Reboot > select Troubleshoot > Advanced Options > UEFI Firmware Settings > (BIOS menu) enable virtualization > Save.

To see the details, go to this HP article: How to Enter BIOS Setup on Windows PCs | HP® Tech Takes

Why you may need to alter the BIOS settings

Well, on my laptop my installation of Debian kept failing with this error. Error: 0x80370102 The virtual machine could not be started because a required feature is not installed. I read on a Microsoft site that could be because the ability to run virtual servers was not enabled in the BIOS. And, yes, that turned out to be absolutely true. It was disabled. So I enabled it and bam, the Debian install started asking me for a username and password, and I was running a Debian VM!

To be fleshed out as my time permits…

But, I love my Debian linux. It’s just like Raspberry Pi OS Lite. I just install packages as I need them: python, pip, curl, bind9-dnsutils, ssh, etc.

Operating inbound TCP services

After the initial thrill wears off, you realize you may need practical things that you have on your Raspberry Pi such as an ssh server or a web server. I believe this will be possible. Still working on it. After installing ssh you can fire it up:

$ sudo service ssh start

This post describes some of those service commands which you have under a WSL linux install: [3 Fixes] System Has Not Been Booted With Systemd as Init System (partitionwizard.com)

If you ignore that article you may see this error! System has not been booted with systemd as init system (PID 1). Can’t operate.

Back to your ssh server. Now you can already connect to it from the Windows system itself, e.g., from a CMD window:

C:\Users\me> ssh user@localhost

user is the Debian user you set during initial setup. So, anyway, that works and that’s cool. But you’re still locked out from the outside.

This helpful Microsoft article discusses networking for WSL2. Apparently it is still evolving and so it’s a bit primitive right now: Accessing network applications with WSL | Microsoft Docs

From a CMD Window launched as administrator:

netsh interface portproxy add v4tov4 listenport=22 listenaddress=0.0.0.0 connectport=22 connectaddress=172.22.167.12

But this does not work in my case. Firewall thing, I’m sure. Yes! for me, where I also run Mcafee, I needed to go to their firewall settings > Ports and system services. Then I had to add a service for TCP port 22 – the ssh default port. Then it began to work and my RPi could ssh and sftp to my Debian VM! sftp kind of hanged a bit. Have to see how bad that is.

References and related

That obnoxious Windows Central article I mentioned above with a lot of the WSL2 installation information. It’s a veritable minefield of links to irrelevant stuff, so you’ve been warned: How to install Linux WSL2 on Windows 10 and Windows 11 | Windows Central

WSL2 kernel update.

Seeing Error: 0x80370102? Try Troubleshooting Windows Subsystem for Linux | Microsoft Docs A whole host of other WSL2 errors are addressed in this article as well.

This article purports to be for servers, but I think it’s applicable to PCs as well. It gets pretty technical. System requirements for Hyper-V on Windows Server | Microsoft Docs

About starting system services such as the ssh daemon: [3 Fixes] System Has Not Been Booted With Systemd as Init System (partitionwizard.com)

A good overview of WSL2 networking: Accessing network applications with WSL | Microsoft Docs

How to Enter BIOS Setup on Windows PCs | HP® Tech Takes

Categories
Python

My favorite Python tips

Intro

I mostly transitioned from perl to python programming. I resisted for the longest time, but now I would never go back. I realized something. I was never really good at Perl. What I was good at were the regular expressions. So Perl for me was just a framework to write RegExes. But Perl code looks ugly with all those semicolons. Python is neater and therefore more legible at a glance. Python also has more libraries to pick from. Data structures in Perl were just plain ugly. I never mastered the syntax. I think I got it now in Python, which is a huge timesaver – I don’t have to hit the books every time I have a complex data structure.

I will probably find these tips useful and will improve upon them as I find better ways to do things. It’s mostly for my own reference, but maybe someone else will find them handy. I use maybe 5% of python? As I need additional things I’ll throw thm in here.

What is this object?

Say you have an object <obj> and want to know what type it is because you’re a little lost. Do:

print(<obj>.__class__)

Check if this key exists in this dict

if “model” in thisdict:

Remove key from dict

if “model” in thisdict: del thisdict[“model”]

Copy (assign) one dict to another

Do not use dict2 = dict1! That is accepted, syntactically, but won’t work as you expect. Instead do this:

dict2 = dict1.copy()

Multiple assignments in on line

a,b,c = “hi”,23,”there”

Key and value from a single line

for itemid,val in itemvals.items():

Formatting

I guess it is pretty common to use a space-based (not tab) indent of four spaces for each subsequent code block.

Initializing lists and dicts

alist = []

adict = {}

Test for an empty list

if not alist: print(“empty list”)

Merge two lists together

for elmnt in list2: list1.append(elmnt)

Conditional operators

if a == b: print(“equals”)

Ternary operator

I don’t think is well-developed in Python and shouldn’t be used (my opinion).

++ operator? Doesn’t exist. += and its ilk does, however.

Boolean variables + multiple assignment example

a, b=True, False

if a==b: print(“equals”)

if a: print(“a is true”)

Reduce number of lines in the program

for n in range(12): colors[n] = ‘red’

if not mykey in mydict: mydict[mykey] = []

Printing stuff while developing

print(“mydict”,mydict,flush=True)

Python figures it out how to print your object, whatever type it is, which is cool. That flush=True is needed if you want to see our output which you’ve redirected to a file right away! Otherwise it gets buffered.

Reading and writing files – prettyify.py
                    

import requests, json, sys, os
import sys,json

from pathlib import Path
aql_file = sys.argv[1]
aql_path = Path(aql_file)
json_file = str(aql_path.with_suffix('.json'))

# Script path
dir_path = os.path.dirname(os.path.realpath(__file__))
dir_path_files = dir_path + "/files/"

# make ugly json file prettier    
# this is kind of a different example, mixed in there
file = sys.argv[1]
f = open(file)
# return json obj as dict
fjson = json.load(f)
nicer = json.dumps(fjson,indent=4)
print(nicer,flush=True)
# back to original example
f = open(dir_path_files + json_file,'w+')
f.write(body)
f.close()

Reading in command-line arguments

See Reading and Writing files example.

Command line tips

The command line is your friend and should be used for little tests. Moreover, you can print an object without even a print statement.

>>>a =[1,’hi’,3]

>>>a

Going from byte object to string

s_b = b’string’

s = s_b.decode(‘utf-8’)

Test if object is a string

if type(thisobject) == str: print(“It is a string”)

Python as a calculator

I always used python command line as a calculator, even ebfore I knew the language syntax! It’s very handy.

>>> 5 + 6/23

Breaking out of a for loop

Use the continue statement after testing a condition.

Executing shell commands

import os

os.system(“ls -l”)

But, to capture the output, you can use the subprocess package.

Accessing environment variables

os.environ.get(‘ENV_TOKEN’)

Handling glob (wildcards) in your shell command

import glob

for query_results_file in glob.glob(os.path.join(dir_path_files,OSpattern)): print(“query_results_file”,query_results_file)

But, if you want the results in the same order as the shell gives, put a sorted() around that. Otherwise the results come out randomly.

JSON tips

Python is great for reading and writing JSON files.

# Load inventory file

with open(dir_path_files + inventory_file) as inventory_file:
inventory_json = json.load(inventory_file)

sitenoted={'gmtOffset':jdict["gmtOffset"],'timezoneId':jdict["timezoneId"]}

# update inventory with custom field Site Notes – put GMT

sitenote=json.dumps(sitenoted)
print("sitenote",sitenote)

Test for null in JSON value

You may see “mykey”:null in your json values. How to test for that?

if my_dict[mykey] == None: continue

RegExes

Although supported in Python, seems kind of ugly. Many RegExes will need to prefaced with r (raw), or else you’ll get yourself into trouble, as in

r'[a-z]{4}.\s*\w(abc|def)’

Function arguments: are they passed by reference or by value?

By reference. But python doesn’t use that terminology. But it means you can pass your complex data structure, say a list of dicts of dicts, start appending to the list in your function, and the calling program has access to the additional members.

Excel files

I’ve been using the package openpyxl quite successfully to read and write Excel files.

Math

numpy seems to be the go-to package.

Python and self-signed certificates, or certificates issued by private CAs

I updated this blog article to help address that: Adding private root CAs in Redhat or SLES or Debian.

Write it with style

Use flake8 to see if your python program conforms to the best practice style. In CentOS I installed flake8 using pip while in Debian linux I installed it using apt-get install flake8.

Can I modify a Python script while its running?

Sure. No worries. It is safe to do so.

Create virtual environment for portability

I like to call my virtual environment venv.

virtualenv venv

Use this virtual environment

source ./venv/bin/activate

List all the packages in this virtual environment

Good portable development style would have you install the minimal set of packages in your virtual environment and then build a requirements.txt file:

pip3 freeze > requirements.txt

Leave this virtual environment

deactivate

Conclusion

I’ve written down some of my favorite tips for using python effectively.

References and related

Adding private root CAs in Redhat or SLES or Debian.

Categories
Consumer Tech

Book Review: extraterrestrial The First Sign of Intelligent Life Beyond Earth

Intro

I don’t normally do book reviews but since someone wanted to get my thoughts on this one, I thought I would share with a broader community.

Source material

Extraterrestrial: The First Sign of Intelligent Life Beyond Earth: Loeb, Avi: 9780358278146: Amazon.com: Books

Let’s get into it

This book is mainly about what to make of the very unusual sighting of an object which came from outside our solar system in 2017, dubbed ‘Oumuamua.

This book is written at a very simple level – perhaps fifth grade or sixth grade? So I guess it’d be a great addition to a middle school library. I was aching for some more details.

I’m actually ready and willing to ‘believe.” For me the main thing was the paucity of facts presented.

The biggest failing of the author is to fail to be so guarded! Professor Avi, you are uniquely qualified to spin any plausible story about this object. Surely you have thought of many origin stories for this thing. Why not share them? This is a book, after all, not a scientific publication. We won’t peer review you for daring to create a plausible backstory for this object.

For me to make my points I have to give some background so everyone sees what I am seeing.

Professor Avi has this super cool lightsail project. Something like 10 GigaWatt lasers are required to send a super slender light sail up to 1/10th the speed of light.

An aside. Wouldn’t a multi Gigawatt blast create a plasma out of the atmosphere, thereby transferring its power to the air rather than the target lightsail? Maybe you overcome that by spreading the laser over a wide area. or using micosecond blasts. Not sure. And what about the reflecting rays? Can they be adequately disbursed to avoid singeing the earth?

But I digress. Sending any macro object to any fraction of the speed of light is wondrous. And dangerous. By conservation of energy I have to assume the thing at that speed would have 10? 100? gigajoules of energy (I will do the math later). Imagine the consequences of an earth-like planet being “visited” by one of those things. Either cataclysmic, or at least terrifying to those lifeforms. Yes, I know the odds of collision are infinitesimal. But they are not zero. And no way can these things be aimed with such precision to avoid that scenario altogether. Not to mention the idea is to send thousands or millions of them out. Welcome to mankind, extraterrestrials, we like to announce our entrance with a bang!

For instance, ‘Oumuamua, though it comes from outside our solar system, is at the local system of rest of the nearby stars. So that is pretty remarkable, and it means its speed is not anywhere close to a fraction of the speed of light, unlike Prof Avi’s lightsails. Why is that? This particular civilization felt they could wait around thousands of years?? Or did it start out at a fraction of the speed of light and then get decelerated as it neared its target? And if so, by what force?

And when I learned it sped up as it zoomed around the sun, I immediately thought of the analogy of our space missions which sometimes use giant planets like Jupiter to pick up speed and slingshot away faster than they had been going. Was ‘Oumuamua purposely aimed near to our sun for its boomerang effect? But it was tumbling like every eight hours. Should lightsails do that? Or does that show if it was a lightsail, it was no longer fit for purpose – inactive space junk? ‘Oumuamua trajectory deviated in the manner a lightsail might. But if it was slowly tumbling, how is that compatible with that statement? Aren’t lightsails only good for catching rays from one orientation? I actually don’t know but that’s what I would naively assume.

And it came from somewhere. if you reverse its trajectory, where did it come from? Was it an area with an inhabitable exoplanet?? Is that area receiving heightened scrutiny from SETI and company??

Going back to these lightsail things travelling at a good fraction of the speed of light, if one were to whip past us, would we even have a chance to see it? I believe it would be effectively invisible to us. How would they fare when colliding with space dust?

A manufactured lightsail would have great symmetry. The brightness profile was not a nice sine function, though close. What is the lightsail shape we can assume given the observed brightness profile fluctuation? A partially destroyed lightsail, perhaps? Where is the artist’s rendering of that?

So you see my point now? Don’t make me speculate. You’re the expert. Your speculations will be grounded in better science than anything I can dream up. So I guess Prof Avi, despite being a maverick in many ways and bucking current scientific thinking in promoting this as a thing created by alien life, reverted to the usual scientist’s conservatism in not making unprovable statements. And we are worse off because of it.

The great filter

And this term bothers me. It reads poorly. The first I heard it was from a fellow reader, and, even though I was familiar with the concept, I had to ask for a definition. A good term of art is self-explanatory. This is not a good term. Advanced civilizations probably last for only a few hundred or at best a few thousand years before they self-destruct. Looking at ourselves, we’re probably only going to get a few hundred the way we’re going. And this is supposed to be the great filter or something? I don’t have a better term, but far more clever people could come up with one I am sure. Like inevitable self-destruction, except something with more of a ring to it.

So I was asked, if this comes from an advanced civilization, is this a cause for hope, or a cause for despair? To argue the despair first, we got space junk from an advanced civilization. Probably they died out and we are left to do astroarchaeology on their junk. Not so great. But I am more hopeful. It’s incredibly difficult to target another star, they managed to do it. Maybe their lightsail had an accident or something. No worries because they sent out millions more like Prof Avi proposes to do. And, the main thing, we overlapped with them! We were advanced enough to detect another’s technology. Mostly because of the self-destruction tendencies, and the randomness of when advanced life forms, we’re not going to have any overlap with the vast majority of our fellow aliens. Their time in the sun was either way in the distant past, or will occur way in the future. That we overlapped in any way at all, probably means there are very, very many advanced civilizations, even in our stellar neighborhood, such that we had decent odds of intercepting and overlapping with one. And that gives me awe and excitement to learn about this advanced life. The hope comes from the viewpoint that these beings aren’t threatening to us. I have a naive belief that they would be trained in cultural sensitivities a la Star Trek The Next Generation or something as opposed to Independence Day, and decide not to wipe us out, nor to alter our technology (much), but more to observe us from afar. So on balance this encounter makes me hopeful.

Any insight if this was a civilization which reached the singularity? I.e., where it transferred its organic intelligence to a program in silicon or some other infinitely long-lasting, purpose-built medium??

So yes I am convinced the simplest explanation is the best one, and prof Avi’s hypothesis is by far the simplest. It raises a few questions which I would have preferred answered. And I was dying for more speculations. The speculations of an insider is worth 100 times the speculations of an outsider such as myself who doesn’t know what they don’t know!!

Philosophy

Prof Avi devotes a lot of time to philosophy. That’s all good. I didn’t learn too much from it, but I suppose others could find it useful. I don’t have an issue with it.

Resources

If I were really responsible, I’d do research, or at least read the darn book reviews on Amazon or get an answer to some of my questions on Quora or something. Probably a lot of my questions are addressed. But my time is not infinite and I’m not trying to impress anyone. As I learn more in the course of my ad hoc reading I will revise this blog with better information. And one more thing about my personal philosophy, I am writing this based solely on self-reflection and readings I’ve absorbed from years ago. I consider active research “cheating” in this regard, and I will inevitably be swayed and biased by the first educated opinion I come across.

Before reading this book, I was aware of this object from 2017 and that it was special, just based on my general reading of science news. It was only from this book that I realized how compelling the extraterrestrial case was.

Prof Avi took a few facts and made a book out of it. He should probably create a fictional but plausible back story for this object and make another book that addresses some of these basic questions.

February 2022 update

They have just discovered signs of a third exoplanet around Proxima Centauri, our nearest neighbor in the galaxy! That’s exciting. The place is only four light years away. Maybe a lightsail craft will visit it within our lifetimes.

Reference and related

Extraterrestrial: The First Sign of Intelligent Life Beyond Earth: Loeb, Avi: 9780358278146: Amazon.com: Books

My cheese grater image of the 2017 eclipse.

Categories
Raspberry Pi

Raspberry Pi Display blanks out after a few seconds

Intro

If you’ve seen any of my many Raspberry Pi photo frame posts, you’ve seen me mention the Pi Display. I recently began having problems with my setup, after many months. I didn’t know if it was the RPi or the display. My display was cracked from abuse anyway so I took the plunge and got a new one. And I re-imaged my micro SD card. I’ll be danged if my brand new display wasn’t blanking out, even as the RPi was still booting! That was frustrating. Here’s how I resolved that. I felt I should publish this article because it’s a little hard to find this exact problem with solution described on the Internet.

The details

The good news is that the Pi Display is still available, incredibly. It comes with absolutely zero documentation. It refers you to element14 or newark web sites, I forget. But those sites just display very generic pages and I couldn’t manage to find any real documentation. I assume the product is considered too old or unsupported or whatever. But since I had bought it already and it seems exactly like the one I was replacing, I went ahead and connected it as before.

Note that the display did not blank out during the installation of Raspbian Lite. That’s a strong hint as to where the problem lies. But after installing that and rebooting, the Pi Display shows bland and white horizontal lines, becomes fainter, and then just blanks out altogether. Rather distressing. I don’t recall this problem from the older versions.

Equipment

I’m still using an old RPi model 3 I have laying around. I guess the new RPi 4 is OK, too. I believe it draws more power though so I actually kind of prefer the old RPi 3’s. You can manage to power both RPi 3 + the PiDisplay from a single power plug if you do it right.

The OS image is Raspberry Pi OS Lite, “bullseye.”

7″ Pi Display – see references.

Random power plug from Amazon. 1.8 amps.

The solution

First, note that I had installed Raspbian bullseye – the latest image as of January 2022. Also note that when connected to an HDMI display, this screen blank-out never occurs! What I needed to do was to connect the RPi to an HDMI display (my TV in my case) and do the sudo apt-get update and sudo apt-get upgrade commands. That recommendation you will find everywhere. In addition, I needed to run raspi-config. In there you navigate to do this navigation:

Display Options > Screen blanking > Would you like to enable screen blanking?

Choose No

I held my breath as I rebooted, and it seemed to want to blank, but then came back a half second later and the display has been illuminated ever since. Now it seems every time I reboot it blanks out as before, during boot, but then “remembers” it’s not supposed to do that and recovers within a second!

How to power both RPi and Pi Display from a single power source

You can connect a short micro USB cable from the USB output of the display to the power input of the RPi – that’s what I do. You could also use the included leads, but I haven’t messed with it.

However, note that – as I found out the hard way – not just any power adapter will do! I started with an Amazon adapter rated for 1 amp. Everything fired up fine, and even ran the slideshow for a bit, but then I guess the power demands were too great and the RPi spontaneously rebooted. So then I switched the system to a larger adapter, also from Amazon – 1.8 amps. So far so good with that one. If that failed, I was prepared with a 2 amp adapter – from a Samsung Galaxy phone. But it seems that will not be necessary.

And this is kind of the beauty of the RPi 3 – you can get away with stuff like that. Your RPi 4 could never do that. It’s a power hog.

Conclusion

The Pi Display is still viable! The price has gone up, but it works. As far as I know in fact it is the “official” display for an RPi. The RPi has a special tab to receive a ribbon cable that connects the two together.

The Pi Display will blank out after a few seconds with newer Raspberry Pi OS images, it seems, even though when paired with an HDMI display this never happens. But it’s easy enough to fix this frustrating problem. Just set screen blanking to No in raspi-config. This ought to better documented on the Internet.

References and related

The Pi Display is a 7″ touch-sensitive LCD display. Its cost is now up to $90. I don’t recommend using its touch capability, but then I don’t like that feature on any display, come to think of it: Amazon.com: Raspberry Pi 7″ Touch Screen Display : Electronics But this latest Pi Display is brighter than my older one. That makes it more visible and enjoyable to watch.

One of my very many posts on creating a photo frame with an RPi and the PiDisplay (but also works fine on HDMI TV’s – I tested it!): https://drjohnstechtalk.com/blog/2021/01/raspberry-pi-photo-frame-using-the-pictures-on-your-google-drive-ii/

Categories
Python Raspberry Pi

Solution to NPR’s puzzle using python

Intro

Of course I’m using my Raspberry Pi. I installed a free dictionary (sudo apt-get install wamerican).

I wanted to practice python, but to not go crazy, so I cheated with some grooming with simple shell commands, e.g.,

$ egrep ‘^[a-z]{5}$’ /usr/share/dict/words > words

That plucks out all the five-letter words and stores them in a local file called words. The original dictionary had about 100,000 “words.” There are about 4000 five-letter words left.

I called the python program v.py. Here it is

                    

import sys,os,re
input = sys.argv[1]
output = []
for character in input:
    number = ord(character) - 96
    output.append(number)
#print(output)
sum=0
for character in input:
    number = ord(character) - 96
    sum += number
#print(sum)
newsum = 0
ends = ''
if sum == 51:
    #print(input)
    for i in input[3:]:
        number = ord(i) - 96
        newsum += number
        ends = ends + i
        #print(i,number,newsum,ends)
    if newsum < 27:
        newl = chr(newsum+96)
        newword = re.sub(ends,newl,input)
        print(input,newword)

I ran it like this:

$ cat words|while read line; do python3 v.py $line >> all-possibilities; done

This plucks out all the five-letter words whose characters add up to 51, and adds the value of the last two letters and creates a new word from them. replacing the last two letters with the new letter.

Drumroll

The results are in.

$ cat all-possibilities

allay allz
avoid avom
bergs berz
beset besy
blocs blov
bombs bomu
broke brop
bused busi
comas comt
condo cons
cribs criu
crude crui
cured curi
dines dinx
elite eliy
erect erew
fates fatx
files filx
flies flix
fluff flul
...
thick thin

Now, go write your own program. I will share the answer when it's too late to submit - it comes towards the end of the list. It sticks out like a sore thumb - nothing else comes close. So if you just persist you'll see it.

Conclusion

I learned a teensy bit of python, my motivation being to solve the current npr puzzle. And it worked! But my program was surprisingly slow. I guess I wrote it in an inefficient manner.

Categories
Admin Linux Raspberry Pi

Scripts checker

Intro

Imagine an infrastructure team empowered to create its own scripts to do such things as regularly update external dynamic lists (EDLs) or interact with APIs in an automated fashion. At some point they will want to have a meta script in place to check the output of the all the automation scripts. This is something I developed to meet that need.

I am getting tired of perl, and I still don’t know python, so I decided to enhance my bash scripting for this script. I learned some valuable things along the way.

checklogs.sh

I call the script checklogs.sh Here it is.

                    

#!/bin/bash
# DrJ 12/2021
# it is desired to run this using the logrotate mechanism
#
# logrotate invokes with /bin/sh so we have to do this trick...
if [ ! "$BASH_VERSION" ] ; then
  exec /bin/bash "$0" "$@"
  exit
fi
DIR=$(cd $(dirname $0);pwd)
INI=$DIR/log.ini
DAY=2 # Day of week to analyze full week of logs. Monday is 1, Tuesday 2, etc
DEBUG=0
maxdiff=10
maxerrors=10
minstarts=10
TMPDIR=/var/tmp
cd $TMPDIR
recipients="john@drjetc.com"
#
checklog2() {
  [[ "$DEBUG" -eq "1" ]] && echo ID, $ID, LPATH, $LPATH, START, $START, ERROR, $ERROR, END, $END
  LPATH="${LPATH}${wildcard}"
  zgrep -Ec "$START" ${LPATH}|cut -d: -f2|while read sline; do starts=$((starts + sline));echo $starts>starts; done
  zgrep -Ec "$END" ${LPATH}|cut -d: -f2|while read sline; do ends=$((ends + sline));echo $ends>ends; done
  zgrep -Ec "$ERROR" ${LPATH}|cut -d: -f2|while read sline; do errors=$((errors + sline));echo $errors>errors; done
  exampleerrors=$(zgrep -E "$ERROR" ${LPATH}|head -10)
  starts=$(cat starts)
  ends=$(cat ends)
  errors=$(cat errors)
  info="${info}===========================================
$ID SUMMARY
  Total starts: $starts
  Total finishes: $ends
  Total errors: $errors
  Most recent errors: "
  info="${info}${exampleerrors}
==========================
"
  unset NEW
# get cumulative totals
  starttot=$((starttot + starts))
  endtot=$((endtot + ends))
  errortot=$((errortot + errors))
  [[ "$DEBUG" -eq "1" ]] && echo starttot, $starttot, endtot, $endtot, errortot, $errortot
  [[ "$DEBUG" -eq "1" ]] || rm starts ends errors
} # end of checklog2 function

checklog() {
# clear out stats and some variables
starttot=0;endtot=0;errortot=0;info=""
#this IFS and following line is trick to preserve those darn backslash charactes in the input file
IFS=$'\n'
for line in $(<$INI); do
  [[ "$line" =~ ^# ]] || {
  pval=$(echo "$line"|sed s'/: */:/')
  lhs=$(echo $pval|cut -d: -f1)
  rhs=$(echo "$pval"|cut -d: -f2-)
  lhs=$(echo $lhs|tr [:upper:] [:lower:])
  [[ "$DEBUG" -eq "1" ]] && echo line is "$line", pval is $pval, lhs is $lhs, rhs is "$rhs"
  if [ "$lhs" = "identifier" ]; then
    [[ "$DEBUG" -eq "1" ]] && echo matched lhs = identifer section
    [[ -n "$NEW" ]] && checklog2
    ID="$rhs"
  fi
  [[ "$lhs" = "path" ]] && LPATH="$rhs" && NEW=false
  [[ "$lhs" = "error" ]] && ERROR="$rhs"
  [[ "$lhs" = "start" ]] && START="$rhs"
  [[ "$lhs" = "end" ]] && END="$rhs"
  }
done
# call one last time at the end
checklog2
} # end of checklog function

anomalydetection() {
# a few tests - you can always come up with more...
  diff=$((starttot - endtot))
  [[ $diff -gt $maxdiff ]] || [[ $starttot -lt $minstarts ]] || [[ $errortot -gt $maxerrors ]] && {
    ANOMALIES=1
    [[ "$DEBUG" -eq "1" ]] && echo ANOMALIES, $ANOMALIES, starttot, $starttot, endtot, $endtot, errortot, $errortot
  }
} # end function anomalydetection

sendsummary() {
  subject="Weekly summary of automation scripts - please review"
  [[ -n "$ANOMALIES" ]] && subject="${subject} - ANOMALIES DETECTED PLEASE REVIEW CAREFULLY!!"

  intro="This summarizes the results from the past week of running automation scripts on script server.
Please check that values seem reasonable. If things are out of range, look at the script server.

"

  [[ "$DEBUG" -eq "1" ]] && echo subject, $subject, intro, "$intro", info, "$info"
  [[ "$DEBUG" -eq "1" ]] && args="-v"
  echo "${intro}${info}"|mail "$args" -s "$subject" $recipients
} # end function sendsummary

# MAIN PROGRAM
# always check the latest log
checklog
anomalydetection

# only check all logs if it is certain day of the week. Monday = 1, etc
day=$(date +%u)
[[ "$DEBUG" -eq "1" ]] && echo day, $day
[[ $day -eq $DAY ]] || [[ -n "$ANOMALIES" ]] && {
  [[ "$DEBUG" -eq "1" ]] && echo calling checklog with wildcard set
  wildcard='*'
  checklog
  sendsummary
}

[[ "$DEBUG" -eq "1" ]] && echo message so far is "$info"

log.ini
                    

# The suggestion: To have a configuration file with log identifiers
#(e.g. “anydesk-edl”) and per identifier: log file path (“/var/log/anydesk-edl.log”),
# error pattern (“.+\[Error\].+”), start pattern (“.+\[Notice\] Starting$”) end pattern (“.+\[Notice\] Done$”).
#Then just count number of executions (based on start/end) and number of errors.

# the start/end/error values are interpreted as extended regular expressions - see regex(7) man page
identifier: anydesk-edl
path: /var/log/anydesk-edl.log
error: .+\[Error\].+
start: .+\[Notice\] Starting$
end: .+\[Notice\] Done$

identifier: firewall-requester-to-edl
path: /var/log/firewall-requester-to-edl.log
error: .+\[Error\].+
start: .+\[Notice\] Starting$
end: .+\[Notice\] Done$

identifier: sase-ips-to-bigip
path: /var/log/sase-ips-to-bigip.log
error: .+\[Error\].+
start: .+\[Notice\] Starting$
end: .+\[Notice\] Done$

What this script does

So when the guy writes an automation script, he is so meticulous that he follows the same convention and hooks it into the syslogger to create uniquely named log files for it. He writes out a [Notice] Starting when his script starts, and a [Notice] Done when it ends. And errors are reported with an [Error] details. Some of the scripts are called hourly. So we agreed to have a script that checks all the other scripts once a week and send a summary email of the results. I look to see that the count of starts and ends is roughly the same, and I report back the ten most recent errors from a given script. I also look for other basic things. That's the purpose of the function anomalydetection in my script. It's just basic tests. I didn't want to go wild.

But what if there was a problem with one of the scripts, wouldn't we want to know sooner than possibly six days later? So I decided to have my script run every day, but only send email on the off days if an anomaly was detected. This made the logic a tad more complex, but nothing bash and I couldn't handle. It fits the need of an overworked operational staff.

Techniques I learned and re-learned from developing this script

cron scheduling - more to it than you thought

I used to naively think that it suffices to look into the crontab files of all users to discover all the scheduled processes. What I missed is thinking about how log rotate works. How does it work? Turns out there is another section of cron for jobs run daily, weekly and monthly. logrotate is called from cron.daily.

logrotate - potential to do more

The person who wrote the automation scripts is a much better scripter than I am. I didn't want to disappoint so I put in the extra effort to discover the best way to call my script. I reasoned that logrotate would offer the opportunity to run side scripts, and I was absolutely right about that! You can run a script just before the logs rotate, or just after. I chose the just before timing - prerotate. In actual fact logrotate calls the prerotate script with all the log files to be rotate as arguments, which you notice we don't take advantage of, because at the time we were unsure how we were going to interface. But I figure let's just leave it now. man logrotate to learn more.

By the way although I developed on a generic Debian system, it should work on a Raspberry Pi as well since it is Debian based.

BASH - the potential to do more, at a price

You'll note that I use some bash-specific extensions in my script. I figure bash is near universal, so why not? The downside is that when logrotate invokes an external script, it calls is using old-fashioned shell. And my script does not work. Except I learned this useful trick:

if [ ! "$BASH_VERSION" ]; then
  exec /bin/bash "$0" "$@"
  exit
fi

Note this is legit syntax in SHELL and a legit conditional operator expression. So it means if you - and by you I mean the script talking about itself - are invoked via SHELL, then invoke yourself via BASH and exit the parent afterwards. And this actually does work (To do: have to check which occurs first, the syntax checking or the command invocation).

More

Speaking of that conditional, if you want to know all the major comparison tests, do a man test. I have around to use the double bracket expressions [[ more and more, though they are BASH specific I believe. The double bracket can be followed by a && and then an open curly brace { which can introduce a block of code delimited of course by a close curly brace }. So for me this is an attractive alternative to SHELL's if conditional then code block fi syntax, and probably just slightly more compact. Replace && with || to execute the code block when the condition does not evaluate to be true.

zgrep is grep for compressed files, but we knew that right? But it's agnostic - it works like grep on both compressed and uncompressed files. That's important because with rotated logs you usually have a combination of both.

Now the expert suggested a certain regular expression for the search string. It wasn't working in my first pass. I reasoned that zgrep may have a special mode to act more like egrep which supports extended regular expressions (EREs). EREs aren't really the same as perl-compatible regular expressions (PCREs) but for this kind of simple stuff we want, they're close enough. And sure enough zgrep has the -E option to force it to interpret the expression as an ERE. Great.

RegEx

So in the log.ini file the regular expression has a \[...\] syntax. The backslash is actually required because otherwise the [...] syntax is interpreted as a character class, where all the characters between the brackets get tried to match a single character in the string to be matched. That's a very different match!

My big thing was - will I have to further escape those lines read in from log.ini, perhaps to replace a \[ with a \\[? Stuff like that happens. I found as long as I used those double quotes around the variables (see below) I did not need to further escape them. Similarly, I found that the EREs in log.ini did not need to be placed between quotes though the guy initially proposed that. It looks cleaner without them.

Variable scope

I wasted a lot of time on a problem which I thought may be due to some weird variable scoping. I've memorized this syntax cat file|while read line; do etc, etc so I use it a lot in my tiny scripts. It's amazing I got away with it as much as I have because it has one huge flaw. if you start using variables within the loop you can't really suck them out, unless you write them to a file. So while at first I thought it was a problem of variable scoping - why do my loop variables have no values when the code comes out of the loop? - it really isn't that issue. It's that the pipe, |, created a forked process which has its own variables. So to avoid that I switched to this weird syntax for line in $(<$INI); do etc. So it does the line-by-line file reading as before but without the pipe and hence without the "variable scope" problem.

But in another place in the script - where I add up numbers - I felt I could not avoid the pipe. So there I do write the value to a file.

The conclusion is that with the caveat that if you know what you're doing, all variables have global scope, and that's just as it should be. Hey, I'm from the old Fortran 66/77 school where we were writing Monte Carlos with thousands of lines of code and dozens of variables in a COMMON block (global scope), and dozens of contributors. It worked just fine thank you very much. Because we knew what we were doing.

Adding numbers in bash

Speaking of adding, I can never remember how to add numbers (integers). In bash you can do starts=$((starts + sline)) , where starts and sline are integers. At least this worked in Debian linux Stretch. I did not really get the same to work so well in SLES Linux - at least not inside a loop where I most needed it.

When you look up how to add numbers in bash there are about a zillion different ways to do it. I'm trying to stick to the built-in way.

Sending mail in Debian linux

You probably need to configure a smarthost if you haven't used your server to send emails up until now. You have to reconfigure of the exim4 package:

dpkg-reconfigure exim4-config

This also can be done on a RPi if you ever find you need for it to send out emails.

Variables

If a variables includes linebreaks and you want to see that, put it between double-quotes, e.g., echo "$myVariableWithLineBreaks". If you don't do that it seems to remove the linebreaks. Use of the double quotes also seems to help avoid mangling variables that contain meta characters found in regular expressions such as .+ or \[.

Result of executing the commands

I grew up using the backtick metacharacter, `, to indicate that the enclosed command should be executed. E.g., old way:

DIR=`dirname $0`

But when you think about it, that metacharacter is small, and often you are unlucky and it sits right alongside a double quote or a single quote, making for a visual trainwreck. So this year I've come to love the use of $(command to be executed) syntax instead. It offers much improved readability. But then the question became, could I nest a command within a command, e.g., for my DIR assignment? I tried it. Now this kind of runs counter to my philosophy of being able to examine every single step as it executes because now I'm executing two steps at once, but since it's pretty straightforward, I went for it. And it does work. Hence the DIR variable is assigned with the compound command:

DIR=$(cd $(dirname $0);pwd)

So now I wonder if you can go more than two levels deep? Each level is an incrementally bad idea - just begging for undetectable mistakes, so I didn't experiment with that!

By the way the reason I needed to do that is that the script jumps around to another directory to create temporary files, and I wanted it to be able to reference the full path to its original directory, so a simpler DIR=$(dirname $0) wasn't going to cut it if it's called with a relative path such as ./checklogs.sh

Debugging

I make mistakes left and right. But I know what results I expect. So I generously insert statements as variables get assigned to double check them, prefacing them with a conditional [[ $DEBUG -eq 1 ]] && print out these values. As I develop DEBUG is set to 1. When it's finally working, I usually set it to 0, though in some script I never quite reach that point. It looks like a lot of typing, but it's really just cut and paste and not over-thinking it for the variable dump, so it's very quick to type.

Another thing I do when I'm stuck is to watch as the script executes in great detail by appending -xv to the first line, e.g., #!/bin/bash -xv. But the output is always confusing. Sometimes it helps though.

Techniques I'd like to use in the future

You can assign a function to a variable and then call that variable. I know that will have lots of uses but I'm not used to the construct. So maybe for my next program.

Conclusion

This fairly simple yet still powerful script has forced me to become a better BASH shell scripter. In this post I review some of the basics that make for successful scripting using the BASH shell. I feel the time invested will pay off as there are many opportunities to write such utility scripts. I actually prefer bash to perl or python for these tasks as it is conceptually simpler, less ambitious, less pretentious, yes, far less capable, but adequate for my tasks. A few rules of the road and you're off and running! bash lends itself to very quick testing cycles. Different versions of bash introduced additional features, and that gets trying. I hope I have found and utilized some of the basic stuff that will be available on just about any bash implementation you are likely to run across.

References and related

The nitty gritty details about BASH shell can be gleaned by doing a man bash. It seems daunting at first but it's really not too bad once you learn how to skim through it.

Categories
Consumer Interest Consumer Tech Uncategorized

Screen Mirroring to Your Smart TV

With the advancements in technology, there are now many features that allow for seamless connection between devices using wireless connections. One of the things that allow this is smart TVs. Currently, the market for them is dominated by South Korean company Samsung. 39% of all sales come from them, which is a huge number in comparison to the 19% from LG and 9.3% from Sony.

There are also devices you can attach to your traditional TV to give it the functions of a smart one, so you won’t have to spend too much to upgrade. With this kind of TV, you can do many different things like stream from platforms like Netflix or Hulu, or even mirror the screen of a mobile device.

What is screen mirroring?


Screen mirroring is basically the ability to project what is on one device to a TV display. This is normally done through the internet and is comparable to connecting a laptop to a monitor using an HDMI cable. As mentioned earlier, there are different ways you can do this. Some TVs have built-in software that allows you to do this, while some use different hardware attachments.

Examples of these accessories are the Amazon Firestick, Apple TV, and Google Chromecast. The last two are some of the most popular ones on the market right now and they both have their own pros and cons. For those already in the Apple ecosystem, using the attachment from the same company will make connecting them easier. If you are looking for a cheaper alternative that can work on almost any device, the Chromecast is your best bet.

These accessories work because of their internet connection. The circuitry is specially designed to deliver signal integrity which ensures that digital and analog signals do not become distorted during propagation. Moreover, this guarantees that the signal can be recovered if temporarily lost, and that screen mirroring is smooth and won’t experience delays.

How to mirror your screen

Make sure your devices are connected to the same internet source


As the feature heavily relies on connection, the only way you can display what is on your other device is by being on the same internet source. Go to the settings of both of your gadgets and connect them to the same wi-fi line. This will make them identifiable to each other and make mirroring possible.

Read the instructions


If you are using a TV box or tool like the Apple TV or Chromecast, make sure to read the connection instructions on the manual. For example, the former requires you to use AirPlay and the manual should teach you which buttons to press on your phone or laptop. For the latter device, you might need a third-party app like the Google Home One to be able to get the accessory to mirror. Be sure to check the instructions given so you can make it a more seamless experience.

Check your Wi-Fi’s integrity


Because mirroring heavily relies on your internet, if the integrity (or speed) that your Wi-Fi is giving out is not enough or lacks bandwidth, you will have a lagging experience. Before you start, try to check the speed of your internet to be sure that it is strong enough. You can simply go on speed test sites on your browser. A good speed would be at least 25mbps, so if it is lower than that, you might not be able to connect or mirror easily.

Screen mirroring is just one-way technology has made life more connected. Gone are the days when other wires and connections were needed. The internet now enables you to perform tasks like projecting from a smaller device to a bigger one, hassle-free.

References and related

Some Firestick problems I’ve encountered are discussed in this post.