How to Send an Email using Telnet

We’ll be using telnet to connect to a mail server and send ourselves an email.

The parts in bold are the commands to enter.

[bob@linux ~]$ telnet mail.website.com 25
Trying mail.website.com...
Connected to mail.website.com.
Escape character is '^]'.
220-mail.website.com ESMTP Exim 4.85 #2 Mon, 09 May 2022 22:12:59 
220-We do not authorize the use of this system to transport unsolicited, 
220 and/or bulk e-mail.
HELO domainto.sendfrom.com
250 mail.website.com Hello domainto.sendfrom.com [192.168.1.2]
MAIL FROM: <bob@incredigeek.com>
250 OK
RCPT TO: <bob@incredigeek.com>
250 Accepted
DATA
354 Enter message, ending with "." on a line by itself
Subject: Test Message

This is a test

.
250 OK id=5a1g7i-1347MT-1p
QUIT
221 mail.website.com closing connection
Connection closed by foreign host.

Further links to read

https://github.com/maildev/maildev/issues/212

Bob lost sudo access on Fedora

Bob has a computer running Fedora. When he installed Fedora he didn’t setup the root password and locked the root account. That is best practice. Right? Then one day he goes to upgrade to the latest version of Fedora and types in

sudo dnf update

and is greeted with

sudoers. This incident will be reported.

What happened? I had access before? Bob thinks to himself. Seems like I am not in the wheel group anymore. Bob being a smart person decides to attempt recovery mode. He’ll boot up and just readd his user to the wheel group.

Recovery mode starts up and then fails due to the root account being locked. What?!

Bob then starts talking to himself as he is in need of some expert advice. What other options do I have. I know! He runs to find his handy dandy Live Fedora pen drive. Plugs it in and boots up into a live version of Fedora. Now I can mount and access the main drive.

But wait, I can’t run “usermod -G wheel bob” because that will only affect the Live System. I could chroot into the drive. That would require mounting some extra mount points. Is there a faster way? We could maybe edit the /etc/group and add “wheel:x:10:bob”. That should add bob back to the wheel group. Right?

Wait, what about the sudoers file. We are normally supposed to use “sudo visudo” command to modify the file. Let’s check the file and see if we can just manually edit it.

$ stat -c "%n %a" /etc/sudoers
/etc/sudoers 440
$
Permissions on /etc/sudoers file

Hmm, okay I am going to need to change permissions to save the file. Let’s chmod that to 644 temporarily

$ sudo chmod 644 /etc/sudoers 

Alright now I should be able to edit it.

$ sudo vi /etc/sudoers

Okay, now I need to explicitly give myself permission to use sudo. Where is that line. Ah-ha!

root    ALL=(ALL)       ALL

Lets duplicate that with yy and p, replace root with my username.

root    ALL=(ALL)       ALL
bob     ALL=(ALL)       ALL

Save that with esc then :wq enter

Now change the file permissions back

sudo chmod 400 /etc/sudoers

Reboot the system and now lets login and test sudo.

$ sudo whoami 
root

Success!

Bob, satisfied that the problem is resolved, rewards himself by getting a sandwich.

sudo make me a sandwich

https://docs.fedoraproject.org/en-US/quick-docs/root-account-locked/

Add directory to path in Linux

Adding a directory to your path is really easy.

The following command adds the ~/script_folder to our PATH paths. Once run, we’ll be able to call any script in the script folder like it was a system utility.

PATH="$HOME/script_folder/:$PATH"

If you would like to always be able to call any file in your scripts folder, add the above command to your ~/.bashrc file.

You may need to restart your session for it to work.

Fix Peertube youtube-dl not Downloading

Issue was not being able to import a video into Peertube using a URL.

Peertube was set up to use youtube-dl which is in /var/www/peertube/storage/bin/youtube-dl. Further investigation showed that Peertube calls it with python.

For example

python youtube-dl video-to-download

Usually Python refers to Python 2 where as Python3 refers to Python 3.

We can create a symlink so that python = python3

sudo ln -s /usr/bin/python3 /usr/bin/python

This way when Peertube runs python, it technically will run it with python3.

Note you will probably run into issues if you do have Python 2 installed and need it. In my case, python was not installed and didn’t reference anything.

Searching for devices in UniFi via command line / MongoDB

While the UniFi controller is nice and everything, it does make it hard to see if a device is already adopted. At least if you have a ton of sites. Fortunately, we can search the database directly to find out if a UniFi is already adopted and which site it is assigned to.

Connect to Mongo DB

First we need to connect to MongoDB. And then we need to use the ace database.

mongo -port 27117
use ace

List all the devices on the controller

This command will list all the devices on the controller. Regardless of which site they are assigned to.

db.device.find({}, { site_id:"", ip : "", name :"", mac:""})

Example output

{ "_id" : ObjectId("563a4d94e4b054e5376fc600"), "mac" : { "_id" : ObjectId("563a4d94e4b054e5376fc600"), "mac" : "44:d9:e7:34:d1:08", "ip" : "192.168.1.200", "name" : "Main_WiFi", "site_id" : "39485e9abf0e9a047bcded96" }
{ "_id" : ObjectId("9873b39ed1f5d30a6738abe"), "mac" : "44:d9:e7:01:a3:d4", "ip" : "192.168.1.201", "name" : "Testing_Wifi", "site_id" : "39485e9abf0e9a047bcded96" }

Each UniFi will have a “site_id”. You can use that ID to figure out which site it is assigned to.

List all the sites on the controller

db.site.find()

Example output

{ "_id" : ObjectId("39485e9abf0e9a047bcded96"), "name" : "default", "desc" : "Testing Site", "attr_hidden_id" : "default", "attr_no_delete" : true, "anonymous_id" : "83ae20ba-2948-458e-fd0a-1320583ecb04" }

Using our “site_id” from above, we see that the Testing_Wifi device is assigned to the “Testing Site” on the controller.

Something else to look at would be to use the UniFi controller API.

https://ubntwiki.com/products/software/unifi-controller/api

Using ADB to Pull APKs off Device

ADB Help for pull and shell

It is sometimes helpful to pull an APK from a working device so you can install it on a different device. These commands should work on an emulator, phone, tablet, or other Android device. You just need to be able to connect with ABD.

  • Connect to device with ADB
  • View installed apps
  • Find path for APK
  • Pull/Download APK

View Installed Apps

This will display a list of all the installed packages.

adb shell pm list packages 

Find path for specific App/APK

Replace com.android.apk with the app of interest.

adb shell pm path com.android.apk

Pull APK to local machine

Pull/Download the APK of interest to your local machine with the following command. Change the path “/data/app/…” to the path returned from the previous command.

adb shell pull /data/app/info/base.apk

You can view the following link for more information.

https://stackoverflow.com/questions/4032960/how-do-i-get-an-apk-file-from-an-android-device

Advanced Tricks

What if you need to get an APK off a secondary profile, or would like to download all the APKs off a system? And what about split APKs?

Multiple User Profiles

Run the following command to list the users.

adb shell pm list users

Example return

Users:
        UserInfo{0:User:a41} running
        UserInfo{11:User:439} running

In this case our second user id is 11. To get a list of APKs installed for our second user we would specify the –user= option

adb shell pm list packages --user=11

To get the path for the app we would run it with

adb shell pm path --user=11 com.android.apk

Split APKs

Split APKs can be slightly more difficult to manage, mainly due to the fact that there are multiple APKs to keep track of.

When you run the “pm path” command, it should return multiple APKs. Use the pull command like normal, but download each APK.

You’ll need to use a split APK installer to install all the APKs.

PowerShell script for Pulling/Downloading all APKs on Device

The following PowerShell script will download all APKs for a specific user and put them in their own folders.

  • Copy the contents to a .ps1 file
  • Enable ps1 execution policy if not already enabled
  • Run PowerShell script.

This script will pull all the APKs off of a device and put them in the current folder.
It will also download split APKs.

# adbapkbackup uses adb to get a list of all the APKs you have on a phone and then
# Creates folders for each app and downloads the APKs for those apps.

# Copy and save code as a ps1 file

# Enable ps1 scripts to run on your computer by launching an Admin promopt and running
# set-executionpolicy remotesigned

# If you are in a secondary profile, add and/or modify
#  "--user 15"
# to your user id
# adb shell pm list users

# If in secondary profile, add "--user 15" after packages before > apklist.txt
adb shell pm list packages --user 15 > apklist.txt

 $apks = ((Get-Content .\apklist.txt)) -replace 'package:',''

 ForEach ($apk in $apks) {
    echo "APK is $apk"
    md $apk
    # If in secondary profile, add "--user 15" after path, before $file
    adb shell pm path $apk
    $filepath = ((adb shell pm path --user 15 $apk | % {$_.replace("package:","")}))
    ForEach ($lapk in $filepath | % {$_.replace("package:","")}) {
        echo "pulling $lapk $apk"
        adb pull $lapk $apk
    }
 }

Identify “Magic Bytes” for Mikroitk Backup File

the “magic bytes” are the first few bytes of a file that can tell you what format the file is.

https://en.wikipedia.org/wiki/List_of_file_signatures

Mikrotik Backup file magic bytes

File typeMagic bytes
RC4 EncryptedEFA89172
AES EncryptedEFA89173
Not Encrypted88ACA1B1

Using the above list, we can view a Mikrotik .backup file in a hex editor like GHex or dump it with xxd.

Setting up Graphana on LibreNMS

Thanks to the guys who put together the information at the following links.

https://wadman.co.nz/2021/01/02/Viewing-LibreNMS-data-in-Grafana/
https://www.reddit.com/r/LibreNMS/comments/ojc8cc/how_to_almost_natively_integrate_librenms_and/

I ran into some issues trying to get this to work. So here are some of my notes. I already had a LibreNMS installation set up.

  1. Install RRDReST
    1. Install Docker
    2. Configure Docker compose file
  2. Configure LibreNMS API User and Key
  3. Set up and Configure Grafana
    1. Install Grafana
    2. Install JSON Data Source Plugin
    3. Add LibreNMS API Data Source
    4. Add RRDReST Data Source
    5. Import Dashboard into Grafana
  4. View graphs

Installing RRDReST

I had issues installing RRDReST. I am guessing it had to do with it accessing files. I was able to install it in a docker container.

  1. Install Docker
  2. Create a compose file
  3. Install container

Install docker

sudo yum install -y docker docker-compose
sudo systemctl enable docker

Create docker compose file with the following options

vi docker-compose.yml

Change the TZ to your time zone. If you have issues with the graphs, most likely something is off with the time zone between this container and Grafana/LibreNMS server

version: "3.5"

services:

  rrdrest:
    image: michaelwadman/rrdrest:latest
    container_name: rrdrest
    restart: always
    volumes:
      - "/opt/librenms:/opt/librenms"
    environment:
      - TZ=America/Denver

Save the file and start and setup the container with

sudo docker-compose up -d

You will need your docker container IP address to setup the connection in Grafana

sudo docker exec -it rrdrest ip addr | grep eth0

Congratulations. You should now have a RRDReST docker container that will auto start on system boot and has the correct time zone.

Configure LibreNMS API User and Key

  1. Create a Grafana user in LibreNMS. (Settings Gear -> Manage Users -> Add Users)
    You could technically skip this step and use an existing user.
  2. Create API token for the newly created user (Setting Gear -> API -> API Settings)
Create a Grafana user in LibreNMS
Setup API Key for Grafana in LibreNMS

Set up and Configure Grafana

Basic steps are as follows

  1. Install Grafana
  2. Install JSON Data Source Plugin
  3. Configure Data Sources
    1. LibreNMS API
    2. RRDRest API
  4. Import Dashboard into Grafana

Install Grafana

There is not anything special with installing Grafana on the same server as LibreNMS. You can follow the official guide to install it

https://grafana.com/docs/grafana/latest/installation/

After Grafana is installed, install the JSON API data source. You can do this using the grafana-cli

grafana-cli plugins install marcusolsson-json-datasource

A note on SSL/TLS certificates. If you have an SSL certificate for LibreNMS, you can use it for grafana. If you run into issues, try copying the cert (fullchain.pem, privkey.pem) to /etc/grafana/

You’ll most likely need to change owner

sudo chown root:grafana /etc/grafana/*.pem

And maybe the file permissions.

sudo chmod 640 /etc/grafana/*.pem

Install JSON Data Source Plugin

This is fairly straight forward.

grafana-cli plugins install marcusolsson-json-datasource

Add LibreNMS API Data Source

In Grafana, go to Configuration -> Data Sources -> Add data source

  • Set Name for Data Source
  • URL should be https://your_librenms_url/api/v0
  • Add Custom HTTP Header
    • Header field should be “X-Auth-Token”
    • Value field should contain the API token we created in LibreNMS
  • Save and Test
    If you receive any errors, refer to the Troubleshooting part at the end.
Adding LibreNMS API Data Source in Grafana

Add RRDReST Data Source

In Grafana, go to Configuration -> Data Sources -> Add data source

  • Set Name for Data Source
  • URL needs to be your docker container IP address (Steps above)
  • Save and Test (Should return “Unprocessable Entity”)
Adding RRDReST API Data Source in Grafana

Import Dashboard into Grafana

Now we need a dashboard to present our data.

  • Go to Create -> Import
  • Upload JSON file (Download from here or PasteBin )
  • Under RRDReST API , select our RRDReST Data Source
  • Under LibreNMS API , select our LibreNMS Data Source
  • Click Import

You should now be able to view your dashboard and use the drop down menus to select devices

Grafana viewing bandwidth on device being monitored by LibreNMS

Troubleshooting

There were a couple of issues I ran into while trying to get everything working together.

RRDReST shows 404 Not Found

Issue: When trying to run RRDReST with uvicorn, I was never able to access the rrd files, even the test rrd files that are included when installing RRDReST. I am guessing it is either a permisions issue, or something unable to access the files.
Work around: Install RRDReST via Docker container.

Error Running uvicorn RRDReST

Error Adding LibreNMS API

Issue: Get a “JSON API: Bad Request” when trying to set up the LibreNMS API Data Source in Grafana.

Work around: Install a valid SSL Certificate and set up a DNS record so you can access LibreNMS at librenms.yourdomain.com.

More info: I would assume that “Skip TLS Verify” would work with or without a valid certificate, but it would not work for me. There are potentially some other options with modifying how Nginx or Apache is set up that would get this working. If you setup Grafana to use a SSL certificate, you may need to copy the certificate files (fullchain.pem, privkey.pem) to /etc/grafana/ and run “chown root:grafana *.pem” to let grafana have access to the files.

Grafana LibreNMS API JSON API: Bad Request

LibreNMS – Package not found: The ‘command_runner>=’

The Problem

Running the ./validate.php script returns the following error

[FAIL]  Python3 module issue found: 'Required packages: ['PyMySQL!=1.0.0', 'python-dotenv', 'redis>=3.0', 'setuptools', 'psutil>=5.6.0', 'command_runner>=1.3.0']
Package not found: The 'command_runner>=1.3.0' distribution was not found and is required by the application
'
        [FIX]:
        pip3 install -r /opt/librenms/requirements.txt

Running the [FIX] throws an error saying gcc failed with exit status 1.

The Solution

Fortunately this issue is easy to resolve.

First we need to install python3-devel

sudo yum install python3-devel

Next, as the librenms user, run the pip command to install the requirements.

pip3 install --user -U -r /opt/librenms/requirements.txt

Run ./validate.php to verify that everything is working.

librenms validate.php results

UniFi UNVR – Recover from Failed USB Drive

Some of the UniFi UNVR’s have system files on a USB drive. There seem to be a number of the drives failing recently, rendering the UNVR inoperable. Fortunately it is easy to replace. The following steps should preserve the video recordings.

https://community.ui.com/questions/UNVR-stopped-responding-just-white-flashing-light/a051f869-8349-4a2a-a72a-ce3a8aa8c759

Steps to recover UNVR

  1. Power off the UNVR
  2. Remove the USB drive (use a heat gun or screw driver to break the glue that is holding the USB drive)
  3. Install new USB drive
  4. Temporarily remove UNVR HDDs (this may not be necessary, but rather be safe then sorry.)
  5. Boot UNVR with new USB drive. (Give it a little time to format and copy contents to the new USB drive. Should not take more then 30 minutes.)
  6. Setup the UNVR like it was before
  7. Power off the UNVR again
  8. Reinstall the HDD’s
  9. Power on the UNVR
  10. Log in and reconfigure the users

Note on Recovery

You could potentially mount the failed or failing USB drive on a Linux machine copy off a UniFi backup. Unfortunately, the UniFi Protect backup does not preserve the users. Just the video groups. You will probably have to resend invites to users.

Note on the video storage drives

It sounds like the UniFi Protect system will try to read the drives and if it can preserve the data or read the raid information it will try to use that. That is what it sounds like at least from the forums. More info on drive management.

https://help.ui.com/hc/en-us/articles/360037340954-UniFi-Hard-drive-compatibility-and-management#h_01F8QE56P7EY1P9FMTZHFZD463