Brennan B2 ssh login

Posted on 18 November 2020 by kosmas

Facebook

Twitter

Problem

You would like to login to your Brennan B2 using your ssh key.

Solution

Copy your public ssh key to /root/.ssh/authorized_keys file in your Brennan B2

SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch

Posted on 23 September 2020 by kosmas

Facebook

Twitter

Problem

Trying to configure and use an nginx server that uses intermediate certifcates, you get the error about values mismatch and nginx does not start

2020/09/23 09:49:38 [emerg] 20958#20958: SSL_CTX_use_PrivateKey(&quot;/etc/ssl/private/cakey.pem&quot;) failed (SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch)

				1

						2020/09/23 09:49:38 [emerg] 20958#20958: SSL_CTX_use_PrivateKey(&quot;/etc/ssl/private/cakey.pem&quot;) failed (SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch)

Solution

It seems that this is a common mistake and it is mentioned here: https://nginx.org/en/docs/http/configuring_https_servers.html. In order to fix this you will need to change/reverse the original order that you have concatenated the chain, as in:

cat certs/cacert.pem intermediate/certs/intermediate.cacert.pem &gt; intermediate/certs/ca-chain-bundle.cert_new.pem

				1

						cat certs/cacert.pem intermediate/certs/intermediate.cacert.pem &gt; intermediate/certs/ca-chain-bundle.cert_new.pem

Decode access secret key from Terraform IAM user creation

Posted on 8 September 2020 by kosmas

Facebook

Twitter

Problem

You want to use the pgp encryption when using Terraform to create an AWS IAM user, and you have the secret access token returned as an output but encoded.

Solution

Use the following to get the actual secret key decoded (after copying your encoded key to a file encrypted_key.txt:

$ cat encrypted_key.txt | base64 --decode | gpg -d

				1

						$ cat encrypted_key.txt | base64 --decode | gpg -d

Raspberry, Ubuntu and Megatools

Posted on 17 June 2020 by kosmas

Facebook

Twitter

To install megtools (command line utilities for Mega.nz), in your raspberry with ubuntu installed follow the steps below (thanks to the instructions from here: https://www.instructables.com/id/Descarga-archivos-de-Mega-con-Raspberry-Pi/)

Install the necessary packages

sudo apt-get -y install build-essential libglib2.0-dev libssl-dev libcurl4-openssl-dev libgirepository1.0-dev 

				1

						sudo apt-get -y install build-essential libglib2.0-dev libssl-dev libcurl4-openssl-dev libgirepository1.0-dev

You may also need to add some additional packages if there is an error about the documentation.

Get the latest source code from https://megatools.megous.com

wget https://megatools.megous.com/builds/megatools-1.10.3.tar.gz

				1

						wget https://megatools.megous.com/builds/megatools-1.10.3.tar.gz

Compile and install them

tar xvfz megatools-1.10.3.tar.gz
cd megatools-1.10.3
./configure
make
sudo make install
sudo ldconfig

				
					
				1
2
3
4
5
6

						tar xvfz megatools-1.10.3.tar.gz
cd megatools-1.10.3
./configure
make
sudo make install
sudo ldconfig

					

			

Add your Mega account credentials in ~/.megarc like:

[Login]
Username = my_mega@email
Password = mypassword

				1
2
3

						[Login]
Username = my_mega@email
Password = mypassword

use the mega tools commands (megacopy, megals, megaget etc.

WiFi, Raspberry Pi 4 B, Ubuntu 20.04

Posted on 10 June 2020 by kosmas

Facebook

Twitter

After installing an image of the Ubuntu server on the Raspberry 4, the wifi is not automatically configured after the initial book.

In order to be able to use the WiFi follow the steps described below for setting up your wifi in your SD card, and then reboot your raspberry (make sure that the indentation in the yaml file is correct, and also your WiFi access point is enclosed in quotes):

https://ubuntu.com/tutorials/how-to-install-ubuntu-on-your-raspberry-pi#3-wifi-or-ethernet

restarting X Window Server from command line in linux

Posted on 2 June 2020 by kosmas

Facebook

Twitter

To restart your X Window Server from the command line in linux, without affecting any non-graphical programs (but losing any unsaved information in your graphical user interface programs), you can use the following:

sudo systemctl restart display-manager

				1

						sudo systemctl restart display-manager

Find devices with their IPs in your local network

Posted on 10 March 2020 by kosmas

Facebook

Twitter

Problem

You would like to have a list of IPs or MAC address for the device in your network

Solution

Use the ARP protocol’s command:

$ arp -a

dv1.home (192.168.1.102) at 48:xx:xx:xx:xx:xx [ether] on wlp4s0
dv2.home (192.168.1.127) at a4:xx:xx:xx:xx:xx [ether] on wlp4s0
...

Find your public IP address from linux command line

Posted on 13 January 2020 by kosmas

Facebook

Twitter

Problem

You would like to find out your public IP from the command line without using an online service

Solution

Use dig like the following line (taken from https://www.cyberciti.biz/faq/how-to-find-my-public-ip-address-from-command-line-on-a-linux/):

dig +short myip.opendns.com @resolver1.opendns.com

you could also add it as an alias:

alias myip=”dig +short myip.opendns.com @resolver1.opendns.com”

Get a list for all crontab jobs in a server

Posted on 6 December 2019 by kosmas

Facebook

Twitter

To get a list of all the installed crontab jobs on a server use the following (taken from https://stackoverflow.com/a/134944)

for user in $(cut -f1 -d: /etc/passwd); do echo $user; crontab -u $user -l; done

Automatic emails using bash and sendgrid

Posted on 24 November 2018 by kosmas

Facebook

Twitter

Problem

You would like to be able to automatically send some emails (ie reports) from a linux server, using a bash script that runs in cronjob, without installing an email server on the linux server.

Solution

Create an account in Sendgrid and follow the directions for using WebAPI with curl
here

Set up your bash script to use the API key and have a script like the following. If you want to use big or multiple files you will need to use a temporary file for the base64 encoding, as in the example below, as there is a limit in curl.

#!/bin/bash

# Email setup
SENDGRID_API_KEY="your_sendgrid_api_key"
FILENAME_ATTACH="title_of_your_attachment"
FILENAME_ZIP="the_path_to_your_zip_file"
FILENAME_BASE64_TMP="the_path_to_temporary_base64_encoding"
EMAIL_TO="email_to_address"
EMAIL_SUBJECT="email_subject"
EMAIL_FROM="email_from_address"
EMAIL_MESSAGE="your_email_message"

function email_exports()
{
  FILENAME_BASE64=$(base64 -w0 $FILENAME_ZIP);

  REQUEST_DATA='{"personalizations": [{
                        "to": [{ "email": "'"$EMAIL_TO"'" }],
                        "subject": "'"$EMAIL_SUBJECT"'"
                }],
                "from": {
                        "email": "'"$EMAIL_FROM"'"
                        },
                "content": [{
                        "type": "text/plain",
                        "value": "'"$EMAIL_MESSAGE"'"
                        }],
                "attachments": [{
                        "content": "'"$FILENAME_BASE64"'",
                        "filename": "'"$FILENAME_ATTACH"'"
                        }]
  }';

  # We need to store the base64 locally as the text
  # is too big for sending directly with curl
   echo $REQUEST_DATA > $FILENAME_BASE64_TMP

   curl -X "POST" "https://api.sendgrid.com/v3/mail/send" \
        -H "Authorization: Bearer $SENDGRID_API_KEY" \
        -H "Content-Type: application/json" \
        -d "@$FILENAME_BASE64_TMP";

   rm $FILENAME_BASE64_TMP
}

email_exports

#!/bin/bash

# Email setup

SENDGRID_API_KEY="your_sendgrid_api_key"

FILENAME_ATTACH="title_of_your_attachment"

FILENAME_ZIP="the_path_to_your_zip_file"

FILENAME_BASE64_TMP="the_path_to_temporary_base64_encoding"

EMAIL_TO="email_to_address"

EMAIL_SUBJECT="email_subject"

EMAIL_FROM="email_from_address"

EMAIL_MESSAGE="your_email_message"

function email_exports()

{

FILENAME_BASE64=$(base64 -w0 $FILENAME_ZIP);

REQUEST_DATA='{"personalizations": [{

"to": [{ "email": "'"$EMAIL_TO"'" }],

"subject": "'"$EMAIL_SUBJECT"'"

}],

"from": {

"email": "'"$EMAIL_FROM"'"

"content": [{

"type": "text/plain",

"value": "'"$EMAIL_MESSAGE"'"

}],

"attachments": [{

"content": "'"$FILENAME_BASE64"'",

"filename": "'"$FILENAME_ATTACH"'"

}]

}';

# We need to store the base64 locally as the text

# is too big for sending directly with curl

echo $REQUEST_DATA > $FILENAME_BASE64_TMP

curl -X "POST" "https://api.sendgrid.com/v3/mail/send" \

-H "Authorization: Bearer $SENDGRID_API_KEY" \

-H "Content-Type: application/json" \

-d "@$FILENAME_BASE64_TMP";

rm $FILENAME_BASE64_TMP

}

email_exports

Add your script to crontab

42

Web notebook about thoughts and discoveries in DevOps, SRE, Software Engineering….

Category Archives: Bash

Brennan B2 ssh login

Problem

Solution

SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch

Problem

Solution

Decode access secret key from Terraform IAM user creation

Raspberry, Ubuntu and Megatools

WiFi, Raspberry Pi 4 B, Ubuntu 20.04

restarting X Window Server from command line in linux

Find devices with their IPs in your local network

Problem

Solution

Find your public IP address from linux command line

Problem

Solution

Get a list for all crontab jobs in a server

Automatic emails using bash and sendgrid