Now let's write the main JS code in order to add menu items into Chrome extension. Create background.js file in the same directory as manifest.json with the content below:

if (chrome && chrome.browserAction){
     var baseUrl = "https://www.example.com"
     chrome.runtime.onInstalled.addListener(function() {
         chrome.tabs.create({ url: baseUrl + "/extension-installed/" });
     });

     chrome.runtime.setUninstallURL(baseUrl + "/extension-uninstalled/");

     // open a new page on left clicking on the extension itself
     chrome.browserAction.onClicked.addListener(function(activeTab) {
         chrome.tabs.create({ url: baseUrl + "/my-home-page" });
     });

     chrome.contextMenus.create({
         "id": "first_item",
         "title": "This is the first item",
         "contexts": ["browser_action"]
     });

     chrome.contextMenus.create({
         "id": "second_item",
         "title": "This is the second item",
         "contexts": ["browser_action"]
     });

     chrome.contextMenus.onClicked.addListener(function(info)
     {
         urls = {
             first_item: baseUrl + "/first-item",
             second_item: baseUrl + "/second-item"
         };
         chrome.tabs.create({url: urls[info.menuItemId]});
     });
 }

There are many events that based on that event you can do an action. Let's review some of the codes above.

chrome.runtime.onInstalled.addListener: on extension installation open a url using chrome.tabs. As you recall from the previous post we have added tabs to the permission section of manifest.

chrome.runtime.setUninstallURL: open a url on extension uninstallation.

chrome.browserAction.onClicked.addListener: open a url when your extension in toolbar is clicked (at the right of the address bar).

chrome.contextMenus.create: create an item with specific id and title. contexts sections tells the browser to show the menu just when user right click on the extension in toolbar. You can add page to have the extension menu item on the main page of browser itself.

chrome.contextMenus.onClicked.addListener: When one of the menu items is clicked open the corresponding URL.

Now to test it go to chrome://extensions/. Make sure developer mode is enabled. Click on Load unpacked and select your extension folder and open it. It will be installed by now.

Enjoy working with Chrome Extension! :)

#chrome #xtension

How to check MongoDB replication lag in Icinga2 and get notified when it is over 15 seconds?

We assume here that you have a replica set in place. First download the python script for our nagios plugin:

cd /usr/lib/nagios/plugins
 git clone git://github.com/mzupan/nagios-plugin-mongodb.git

Now the Icinga2 part. You first need to create a command for replication lag check:

cd /etc/icinga2/conf.d/commands

Create a new file replication_lag.conf:

object CheckCommand "check_replication_lag" {
     import "plugin-check-command"
     command = [ PluginDir + "/nagios-plugin-mongodb/check_mongodb.py", "-A", "replication_lag" ]
     arguments = {
         "-H" = "$mongo_host$"
         "-P" = "$mongo_port$"
     }
 }

Create a new file in services folder called replication_lag.conf:

apply Service for (display_name => config in host.vars.replication) {
     import "generic-service"
     check_command = "check_replication_lag"
     vars += config
     assign where host.vars.replication
 }

This service gets enabled where it finds replication in host config. Now in secondary mongoDB hosts configuration add the below part:

vars.replication["Secondary DB"] = {
     mongo_host = "slave.example.com"
     mongo_port = 27017
 }

#sysadmin #icinga2 #mongodb #replication #replication_lag #nagios_plugin

I have a script that checks a source folder for new files in case there are files in the source folder, it will move those files to destination.

The problem I encountered recently was that files are huge and it may be in the middle of the copying into source by another process so my script tries to move an incomplete file to a destination. Let's say the file is 4GB in size and just only 1GB of the file has been copied. I have to wait until file is 4GB and other handler using that file, then I should safely move the file.

You can use lsof command in order to check which processes are using the source file:

if [[ `lsof -- /var/my-folder/my-big-file.tar.gz` ]]
then
     echo "File is being used by a process."
     exit 1
 fi

NOTE: you can give file directly to lsof using -- or you can use grep command as follow:

lsof | grep /var/my-folder/my-big-file.tar.gz

NOTE2: if you are in a loop use break instead of exit.

NOTE3: if you get command not found, install it using apt-get install lsof

#linux #sysadmin #lsof #grep

How to upgrade Axigen mail server?

The procedure is dead simple! Mail server itself notifies you about the new updates in its admin panel. Head over to the given link and download the the appropriate file related to your OS. Usually a .run file.

1- First make it executable:

chmod +x axigen-10.2.2.x86_64.rpm.run

NOTE: here my version update may differ from yours.

2- Now stop Axigen.

3- Run the installer and go in an interactive way. JUST be sure to skip the Axigen post-install configuration wizard.

4- Now start Axigen.

NOTE: in case you want to take backup copy the folder /var/opt/axigen in a safe place. This path may differ based on your OS and your distro.

#mail_server #axigen #upgrade #update

Have you heard about CORS (Cross Origin Resource Sharing)?

If you know it, but like me you don't know it as you should and every time the bowser gives you a new error in console you again get wandered in the wilderness, I'd suggest going to the awesome link below and read thoroughly line by line:

https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS

NOTE: this article is fantastic! Believe you me. You will understand eveything you need to know exactly what is CORS and how to handle it properly.


#browser #mozilla #CORS #cross_origin #cross_origin_resource_sharing

nginX by default does not set CORS headers for requests with error status codes like 401. There are 2 options here to add CORS headers:

1- If your nginX version is new you have the option of always to add to add_header:

add_header 'Access-Control-Allow-Origin' $http_origin always;

2- If you got error of invalid number of arguments in "add_header" directive, then use more_set_headers:

more_set_headers -s '401 400 403 404 500' 'Access-Control-Allow-Origin: $http_origin';

NOTE: when this error happens then in $.ajax or any similar method you wont have access to status codes. So be extremely catious!!!

#nginX #web_server #CORS #more_set_headers #add_header #ajax

How to upload a text content as a file in $.Ajax()?

FormData class is used to create a multipart/form-data inside of JS code. A sample code speaks thousand words:

var formData = new FormData();
 var blob = new Blob([YOUR_CONTENT_HERE], { type: "text/html"});
 formData.append("file", blob);

We have created a binary data from the text which is in the format of text/html, then I have appended the data as an input file with the name of file (which will be captured on server-side).

The Ajax part is utterly simple:

$.ajax({
     type: 'POST',
     url: 'https://www.example.com/storage',
     data: formData,
     processData: false,
     contentType: false
 }).done(function(data) {});

NOTE: DO NOT OMIT processData, contentType parameters.

#javascript #jQuery #ajax #FormData #Blob #upload

Does that happen for you too, to CD into a wrong directory and need to get back to the previous directory?

Let's say you are in a long path like /mnt/new_volume/backup/files/archive, now you switch to home of your directory. In order to get back to the previous directory, you just need to issue the below command:

cd -

#linux #cd

https://spyhce.com/blog/understanding-new-and-init

#python27 #python3 #__init__ #__new__ #old_style #new_style #OOP #class #super

How to convert ByteArray to PDF and then upload it via jQuery?

var docData = [ yourByteArray ];
 var blob = new Blob([new Uint8Array(docData)], { type: 'application/pdf' });

 // Now create form to upload the file
 var formData = new FormData();
 formData.append("file", blob);

 // Let's now upload the file
 $.ajax({
         type: 'POST',
         url: 'https://www.YOUR-UPLOAD-FILE-ENDPOINT.com/storage',
         beforeSend: request => set_ajax_headers(request),
         data: formData,
         processData: false,
         contentType: false
     }).done(function(data) {
         console.log('File is uploaded!');
     });

NOTE: function set_ajax_headers is a function that sets headers on the given request.

#javascript #ByteArray #PDF #Uint8Array #Blob #jQuery

How to SSH login without password?

You want to use Linux and OpenSSH to automate your tasks. Therefore you need an automatic login from host A / user a to Host B / user b. You don't want to enter any passwords, because you want to call ssh from a within a shell script.

How to do it?
First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again: 
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password:

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password:

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B

#linux #sysadmin #ssh #password_less #ssh_login

Virt-builder is a tool for quickly building new virtual machines. You can build a variety of VMs for local or cloud use, usually within a few minutes or less. Virt-builder also has many ways to customize these VMs. Everything is run from the command line and nothing requires root privileges, so automation and scripting is simple.

To see available virtual machines:

virt-builder --list

Sample command to create a debian-9 image:

sudo virt-builder debian-9 --size=50G --hostname prod.example.com --network --install network-manager --root-password password:YOUR_PASS

The above command creates a debian 9 image with disk size of 50GB and sets the hostname to prod.example.com. --network enables the networking on guest and --install installs packages on the target O
S. The last parameter sets the root password to YOUR_PASS.

To read more about the axtra parameters:
- https://libguestfs.org/virt-builder.1.html

#linux #sysadmin #virt_builder #debian #image

https://superuser.com/questions/453988/whats-the-difference-between-su-with-and-without-hyphen

#linux #su

Enable workmode in Telegram:

open settings in telegram desktop and without clicking anywhere type workmode a dialog will open to confirm that want it to be enabled. After telegram restart you willl have a new bar above chat accounts -> Hide muted chats click on it to hide muted chats from the left pane.

Spread your love for m2sh :)

#telegram #trick #fun #workmode #work_mode

https://hackernoon.com/python-3-7s-new-builtin-breakpoint-a-quick-tour-4f1aebc444c

#python #python37 #breakpoint #pdb #set_trace

https://realpython.com/python-data-classes/

#python #python37 #data_classes #dataclasses

For prometheus you can use an alert manager, it has a docker file in the link below:
- https://hub.docker.com/r/prom/alertmanager

Awesome Prometheus alerts:
- https://github.com/samber/awesome-prometheus-alerts

alertmanager has rules, you can see sample rules here in the following link:
- https://awesome-prometheus-alerts.grep.to/rules

So to add alertmanager service:

alertmanager:
    image: prom/alertmanager:latest
    restart: always
    command: --config.file=/etc/alertmanager/alertmanager.yml
    volumes:
      - ./alert/config/alertmanager.yml:/etc/alertmanager/alertmanager.yml
    dns:
      - 8.8.8.8

You alert manager configuration may look something like below:

global:
  resolve_timeout: 5m

route:
  # When a new group of alerts is created by an incoming alert, wait at
  # least 'group_wait' to send the initial notification.
  # This way ensures that you get multiple alerts for the same group that start
  # firing shortly after another are batched together on the first
  # notification.
  group_wait: 10s

  # When the first notification was sent, wait 'group_interval' to send a betch
  # of new alerts that started firing for that group.
  group_interval: 5m

  # If an alert has successfully been sent, wait 'repeat_interval' to
  # resend them.
  repeat_interval: 30m

  # A default receiver
  receiver: "slack"

  # All the above attributes are inherited by all child routes and can
  # overwritten on each.
  routes:
    - receiver: "slack"
      group_wait: 10s
      match_re:
        severity: error|warning
      continue: true

#    - receiver: "sms"
#      group_wait: 10s
#      match_re:
#        severity: error
#      continue: true

receivers:
  - name: "slack"
    slack_configs:
      - api_url: 'YOUR-WEBHOOK-URL'
        send_resolved: true
        channel: 'monitoring'
        text: "{{ range .Alerts }}<!channel> {{ .Annotations.summary }}\n{{ .Annotations.description }}\n{{ end }}"

#  - name: "sms"
#    webhook_config:
#      - url: https://a.b.c:8080/send/sms
#        send_resolved: true

You should be up & running with this sample configurations.
Spread your love for M2SH :)

#prometheus #prom #alert #alert_manager #docker #dockerfile #slack

Echo: High performance, minimalist Go web framework
- https://echo.labstack.com
- https://github.com/labstack/echo

A sample hello-world web server using Echo:

package main

import (
  "net/http"
  "github.com/labstack/echo/v4"
  "github.com/labstack/echo/v4/middleware"
)

func main() {
  // Echo instance
  e := echo.New()

  // Middleware
  e.Use(middleware.Logger())
  e.Use(middleware.Recover())

  // Routes
  e.GET("/", hello)

  // Start server
  e.Logger.Fatal(e.Start(":1323"))
}

// Handler
func hello(c echo.Context) error {
  return c.String(http.StatusOK, "Hello, World!")
}