Use Mailx to send emails using office 365

just something that came up while setting up a monitoring script using mailx, figured ill note it down here so i can get it to easily later when I need it 😀

Important prerequisites

  • You need to enable smtp basic Auth on Office 365 for the account used for authentication
  • Create an App password for the user account
  • nssdb folder must be available and readable by the user running the mailx command

Assuming all of the above prerequisite are $true we can proceed with the setup

Install mailx

RHEL/Alma linux

sudo dnf install mailx

NSSDB Folder

make sure the nssdb folder must be available and readable by the user running the mailx command

certutil -L -d /etc/pki/nssdb

The Output might be empty, but that’s ok; this is there if you need to add a locally signed cert or another CA cert manually, Microsoft Certs are trusted by default if you are on an up to date operating system with the local System-wide Trust Store

Reference – RHEL-sec-shared-system-certificates

Configure Mailx config file

sudo nano /etc/mail.rc

Append/prepend the following lines and Comment out or remove the same lines already defined on the existing config files

set smtp-auth-user=###[email protected]###
set smtp-auth-password=##Office365-App-password#
set nss-config-dir=/etc/pki/nssdb/
set ssl-verify=ignore
set smtp-use-starttls
set from="###[email protected]###"

This is the bare minimum needed other switches are located here – link


echo "Your message is sent!" | mailx -v -s "test" [email protected]

-v switch will print the verbos debug log to console

Connecting to . . . connected.
220 Microsoft ESMTP MAIL Service ready at Sun, 6 Aug 2023 22:14:56 +0000
>>> EHLO vls-xxx.multicastbits.local Hello []
250-SIZE 157286400
220 2.0.0 SMTP server ready
>>> EHLO vls-xxx.multicastbits.local Hello []
250-SIZE 157286400
334 VXNlcm5hbWU6
>>> Zxxxxxxxxxxxc0BmdC1zeXMuY29t
334 UGsxxxxxmQ6
>>> c2Rxxxxxxxxxxducw==
235 2.7.0 Authentication successful
>>> MAIL FROM:<###[email protected]###>
250 2.1.0 Sender OK
>>> RCPT TO:<[email protected]>
250 2.1.5 Recipient OK
>>> DATA
354 Start mail input; end with <CRLF>.<CRLF>
>>> .
250 2.0.0 OK <[email protected]> []
>>> QUIT
221 2.0.0 Service closing transmission channel 

Now you can use this in your automation scripts or timers using the mailx command


recipient="[email protected]"
subject="Log file from /etc/app/runtime.log"

# Check if the log file exists
if [ ! -f "$log_file" ]; then
  echo "Error: Log file not found: $log_file"
  exit 1

# Use mailx to send the log file as an attachment
echo "Sending log file..."
mailx -s "$subject" -a "$log_file" -r "[email protected]" "$recipient" < /dev/null
echo "Log file sent successfully."

Secure it

sudo chown root:root /etc/mail.rc
sudo chmod 600 /etc/mail.rc

The above commands change the file’s owner and group to root, then set the file permissions to 600, which means only the owner (root) has read and write permissions and other users have no access to the file.

Use Environment Variables: Avoid storing sensitive information like passwords directly in the mail.rc file, consider using environment variables for sensitive data and reference those variables in the configuration.

For example, in the mail.rc file, you can set:

set smtp-auth-password=$MY_EMAIL_PASSWORD

You can set the variable using another config file or store it in the Ansible vault during runtime or use something like Hashicorp.

Sure, I would just use Python or PowerShell core, but you will run into more locked-down environments like OCI-managed DB servers with only Mailx is preinstalled and the only tool you can use 🙁

the Fact that you are here means you are already in the same boat. Hope this helped… until next time

Solution – RKE Cluster MetalLB provides Services with IP Addresses but doesn’t ARP for the address

I ran in to the the same issue detailed here working with a RKE cluster

After looking around for a few hours digging in to the logs i figured out the issue, hopefully this helps some one else our there in the situation save some time.

Make sure the IPVS mode is enabled on the cluster configuration

If you are using :

RKE2 – edit the cluster.yaml file

RKE1 – Edit the cluster configuration from the rancher UI > Cluster management > Select the cluster > edit configuration > edit as YAML

Locate the services field under rancher_kubernetes_engine_config and add the following options to enable IPVS

        ipvs-scheduler: lc
        proxy-mode: ipvs


After changes

Make sure the Kernel modules are enabled on the nodes running control planes


Example Rancher – RKE1 cluster

sudo docker ps | grep proxy # find the container ID for kubproxy

sudo docker logs ####containerID###

0313 21:44:08.315888  108645 feature_gate.go:245] feature gates: &{map[]}
I0313 21:44:08.346872  108645 proxier.go:652] "Failed to load kernel module with modprobe, you can ignore this message when kube-proxy is running inside container without mounting /lib/modules" moduleName="nf_conntrack_ipv4"
E0313 21:44:08.347024  108645 server_others.go:107] "Can't use the IPVS proxier" err="IPVS proxier will not be used because the following required kernel modules are not loaded: [ip_vs_lc]"

Kubproxy is trying to load the needed kernel modules and failing to enable IPVS

Lets enable the kernel modules

sudo nano /etc/modules-load.d/ipvs.conf


Install ipvsadm to confirm the changes

sudo dnf install ipvsadm -y

Reboot the VM or the Baremetal server

use the sudo ipvsadm to confirm ipvs is enabled

sudo ipvsadm


kubectl get svc -n #namespace | grep load
arping -I ens192
ARPING from ens192
Unicast reply from [00:50:56:96:E3:1D] 1.117ms
Unicast reply from [00:50:56:96:E3:1D] 0.737ms
Unicast reply from [00:50:56:96:E3:1D] 0.845ms
Unicast reply from [00:50:56:96:E3:1D] 0.668ms
Sent 4 probes (1 broadcast(s))
Received 4 response(s)

If you have the service type load balancer on a deployment now you should be able to reach it if the container is responding on the service

helpful Links

How to extend root (cs-root) Filesystem using LVM Cent OS/RHEL/Almalinux

This guide will walk you through on how to extend and increase space for the root filesystem on a alma linux. Cent OS, REHL Server/Desktop/VM

Method A – Expanding the current disk

Edit the VM and Add space to the Disk

install the cloud-utils-growpart package, as the growpart command in it makes it really easy to extend partitioned virtual disks.

sudo dnf install cloud-utils-growpart

Verify that the VM’s operating system recognizes the new increased size of the sda virtual disk, using lsblk or fdisk -l

sudo fdisk -l
Notes -
Note down the disk id and the partition number for Linux LVM - in this demo disk id is sda and lvm partition is sda 3

lets trigger a rescan of a block devices (Disks)

#elevate to root
sudo su 

#trigger a rescan, Make sure to match the disk ID you noted down before 
echo 1 > /sys/block/sda/device/rescan

Now sudo fdisk -l shows the correct size of the disks

Use growpart to increase the partition size for the lvm

sudo growpart /dev/sda 3

Confirm the volume group name

sudo vgs

Extend the logical volume

sudo lvextend -l +100%FREE /dev/almalinux/root

Grow the file system size

sudo xfs_growfs /dev/almalinux/root
Notes -
You can use this same steps to add space to different partitions such as home, swap if needed

Method B -Adding a second Disk to the LVM and expanding space

Why add a second disk?
may be the the current Disk is locked due to a snapshot and you cant remove it, Only solution would be to add a second disk/

Check the current space available

sudo df -h 
Notes -
If you have 0% ~1MB left on the cs-root command auto-complete with tab and some of the later commands wont work, You should clear up atleast 4-10mb by clearing log files, temp files, etc

Mount an additional disk to the VM (Assuming this is a VM) and make sure the disk is visible on the OS level

sudo lvmdiskscan


sudo fdisk -l

Confirm the volume group name

sudo vgs

Lets increase the space

First lets initialize the new disk we mounted

sudo mkfs.xfs /dev/sdb

Create the Physical volume

sudo pvcreate /dev/sdb

extend the volume group

sudo vgextend cs /dev/sdb
  Volume group "cs" successfully extended

Extend the logical volume

sudo lvextend -l +100%FREE /dev/cs/root

Grow the file system size

sudo xfs_growfs /dev/cs/root

Confirm the changes

sudo df -h

Just making easy for us!!

#Method A - Expanding the current disk 
sudo dnf install cloud-utils-growpart

sudo lvmdiskscan
sudo fdisk -l                          #note down the disk ID and partition num

sudo su                                #elevate to root
echo 1 > /sys/block/sda/device/rescan  #trigger a rescan
exit                                   #exit root shell

sudo lvextend -l +100%FREE /dev/almalinux/root
sudo xfs_growfs /dev/almalinux/root
sudo df -h

#Method B - Adding a second Disk 

sudo lvmdiskscan
sudo fdisk -l
sudo vgs
sudo mkfs.xfs /dev/sdb
sudo pvcreate /dev/sdb
sudo vgextend cs /dev/sdb
sudo lvextend -l +100%FREE /dev/cs/root
sudo xfs_growfs /dev/cs/root
sudo df -h


sudo lvmdiskscan
sudo fdisk -l
sudo vgs
sudo mkfs.xfs /dev/sdb
sudo pvcreate /dev/sdb
sudo vgextend almalinux /dev/sdb
sudo lvextend -l +100%FREE /dev/almalinux/root
sudo xfs_growfs /dev/almalinux/root
sudo df -h

Setup guide for VSFTPD FTP Server – SELinux enforced with fail2ban (RHEL, CentOS, Almalinux)

Few things to note

  • if you want to prevent directory traversal we need to setup chroot with vsftpd (not covered on this KB)
  • For the demo I just used Unencrypted FTP on port 21 to keep things simple, Please utilize SFTP with the letsencrypt certificate for better security. i will cover this on another article and link it here

Update and Install packages we need

sudo dnf update
sudo dnf install net-tools lsof unzip zip tree policycoreutils-python-utils-2.9-20.el8.noarch vsftpd nano setroubleshoot-server -y

Setup Groups and Users and security hardening

if you want to prevent directory traversal we need to setup chroot with vsftpd (not covered on this KB)

Create the Service admin account

sudo useradd ftpadmin
sudo passwd ftpadmin

Create the group

sudo groupadd FTP_Root_RW

Create FTP only user shell for the FTP users

echo -e '#!/bin/sh\necho "This account is limited to FTP access only."' | sudo tee -a /bin/ftponly
sudo chmod a+x /bin/ftponly

echo "/bin/ftponly" | sudo tee -a /etc/shells

Create FTP users

sudo useradd ftpuser01 -m -s /bin/ftponly
sudo useradd ftpuser02 -m -s /bin/ftponly
user passwd ftpuser01 
user passwd ftpuser02

Add the users to the group

sudo usermod -a -G FTP_Root_RW ftpuser01
sudo usermod -a -G FTP_Root_RW ftpuser02

sudo usermod -a -G FTP_Root_RW ftpadmin

Disable SSH Access for the FTP users.

Edit sshd_config

sudo nano /etc/ssh/sshd_config

Add the following line to the end of the file

DenyUsers ftpuser01 ftpuser02

Open ports on the VM Firewall

sudo firewall-cmd --permanent --add-port=20-21/tcp

#Allow the passive Port-Range we will define it later on the vsftpd.conf
sudo firewall-cmd --permanent --add-port=60000-65535/tcp

#Reload the ruleset
sudo firewall-cmd --reload

Setup the Second Disk for FTP DATA

Attach another disk to the VM and reboot if you haven’t done this already

lsblk to check the current disks and partitions detected by the system


Create the XFS partition

sudo mkfs.xfs /dev/sdb
# use mkfs.ext4 for ext4

Why XFS?

Create the folder for the mount point

sudo mkdir /FTP_DATA_DISK

Update the etc/fstab file and add the following line

sudo nano etc/fstab
/dev/sdb /FTP_DATA_DISK xfs defaults 1 2

Mount the disk

sudo mount -a


mount | grep sdb

Setup the VSFTPD Data and Log Folders

Setup the FTP Data folder

sudo mkdir /FTP_DATA_DISK/FTP_Root -p

Create the log directory

sudo mkdir /FTP_DATA_DISK/_logs/ -p

Set permissions

sudo chgrp -R FTP_Root_RW /FTP_DATA_DISK/FTP_Root/
sudo chmod 775 -R /FTP_DATA_DISK/FTP_Root/

Setup the VSFTPD Config File

Backup the default vsftpd.conf and create a newone

sudo mv /etc/vsftpd/vsftpd.conf /etc/vsftpd/vsftpdconfback
sudo nano /etc/vsftpd/vsftpd.conf
#KB Link - ####

ftpd_banner=Welcome to multicastbits Secure FTP service.




Add the FTP users to the userlist file

Backup the Original file

sudo mv /etc/vsftpd/user_list /etc/vsftpd/user_listBackup
echo "ftpuser01" | sudo tee -a /etc/vsftpd/user_list
echo "ftpuser02" | sudo tee -a /etc/vsftpd/user_list
sudo systemctl start vsftpd

sudo systemctl enable vsftpd

sudo systemctl status vsftpd

Setup SELinux

instead of putting our hands up and disabling SElinux, we are going to setup the policies correctly

Find the available policies using getsebool -a | grep ftp

getsebool -a | grep ftp

ftpd_anon_write --> off
ftpd_connect_all_unreserved --> off
ftpd_connect_db --> off
ftpd_full_access --> off
ftpd_use_cifs --> off
ftpd_use_fusefs --> off
ftpd_use_nfs --> off
ftpd_use_passive_mode --> off
httpd_can_connect_ftp --> off
httpd_enable_ftp_server --> off
tftp_anon_write --> off
tftp_home_dir --> off
[lxadmin@vls-BackendSFTP02 _logs]$ 
[lxadmin@vls-BackendSFTP02 _logs]$ 
[lxadmin@vls-BackendSFTP02 _logs]$ getsebool -a | grep ftp
ftpd_anon_write --> off
ftpd_connect_all_unreserved --> off
ftpd_connect_db --> off
ftpd_full_access --> off
ftpd_use_cifs --> off
ftpd_use_fusefs --> off
ftpd_use_nfs --> off
ftpd_use_passive_mode --> off
httpd_can_connect_ftp --> off
httpd_enable_ftp_server --> off
tftp_anon_write --> off
tftp_home_dir --> off

Set SELinux boolean values

sudo setsebool -P ftpd_use_passive_mode on

sudo setsebool -P ftpd_use_cifs on

sudo setsebool -P ftpd_full_access 1

    "setsebool" is a tool for setting SELinux boolean values, which control various aspects of the SELinux policy.

    "-P" specifies that the boolean value should be set permanently, so that it persists across system reboots.

    "ftpd_use_passive_mode" is the name of the boolean value that should be set. This boolean value controls whether the vsftpd FTP server should use passive mode for data connections.

    "on" specifies that the boolean value should be set to "on", which means that vsftpd should use passive mode for data connections.

    Enable ftp_home_dir --> on if you are using chroot

Add a new file context rule to the system.

sudo semanage fcontext -a -t public_content_rw_t "/FTP_DATA_DISK/FTP_Root/(/.*)?"
    "fcontext" is short for "file context", which refers to the security context that is associated with a file or directory.

    "-a" specifies that a new file context rule should be added to the system.

    "-t" specifies the new file context type that should be assigned to files or directories that match the rule.

    "public_content_rw_t" is the name of the new file context type that should be assigned to files or directories that match the rule. In this case, "public_content_rw_t" is a predefined SELinux type that allows read and write access to files and directories in public directories, such as /var/www/html.

    "/FTP_DATA_DISK/FTP_Root/(/.)?" specifies the file path pattern that the rule should match. The pattern includes the "/FTP_DATA_DISK/FTP_Root/" directory and any subdirectories or files beneath it. The regular expression "/(.)?" matches any file or directory name that may follow the "/FTP_DATA_DISK/FTP_Root/" directory path.

In summary, this command sets the file context type for all files and directories under the "/FTP_DATA_DISK/FTP_Root/" directory and its subdirectories to "public_content_rw_t", which allows read and write access to these files and directories.

Reset the SELinux security context for all files and directories under the “/FTP_DATA_DISK/FTP_Root/”

sudo restorecon -Rvv /FTP_DATA_DISK/FTP_Root/
    "restorecon" is a tool that resets the SELinux security context for files and directories to their default values.

    "-R" specifies that the operation should be recursive, meaning that the security context should be reset for all files and directories under the specified directory.

    "-vv" specifies that the command should run in verbose mode, which provides more detailed output about the operation.

"/FTP_DATA_DISK/FTP_Root/" is the path of the directory whose security context should be reset.

Setup Fail2ban

Install fail2ban

sudo dnf install fail2ban

Create the jail.local file

This file is used to overwrite the config blocks in /etc/fail2ban/fail2ban.conf
sudo nano /etc/fail2ban/jail.local
enabled = true
port = ftp,ftp-data,ftps,ftps-data
logpath = /FTP_DATA_DISK/_logs/vsftpd.log
maxretry = 5
bantime = 7200

Make sure to update the logpath directive to match the vsftpd log file we defined on the vsftpd.conf file

sudo systemctl start fail2ban

sudo systemctl enable fail2ban

sudo systemctl status fail2ban
journalctl -u fail2ban  will help you narrow down any issues with the service


sudo tail -f /var/log/fail2ban.log

Fail2ban injects and manages the following rich rules

Client will fail to connect using FTP until the ban is lifted

Remove the ban IP list

#get the list of banned IPs 
sudo fail2ban-client get vsftpd banned

#Remove a specific IP from the list 
sudo fail2ban-client set vsftpd unbanip <IP>

#Remove/Reset all the the banned IP lists
sudo fail2ban-client unban --all

This should get you up and running, For the demo I just used Unencrypted FTP on port 21 to keep things simple, Please utilize SFTP with the letsencrypt certificate for better security. i will cover this on another article and link it here

External Pi-hole with IPv6 – Setup a secured Pi-hole DNS service on Docker using Linode/AWS

Let me address the question of why I decided to put a DNS server (Pihole) exposed to the internet (not fully open but still).

I needed/wanted to set up an Umbrella/NextDNS/CF type DNS server that’s publicly accessible but secured to certain IP addresses.

Sure NextDNS is an option and its cheap with similar features, but i wanted roll my own solution so i can learn a few things along the way

I can easily set this up for my family members with minimal technical knowledge and unable to deal with another extra device (Raspberry pi) plugged into their home network.

This will also serve as a quick and dirty guide on how to use Docker compose and address some Issues with Running Pi-hole, Docker with UFW on Ubuntu 20.x

So lets get stahhhted…….


  • Setup Pi-hole as a docker container on a VM
  • Enable IPV6 support
  • Setup UFW rules to prune traffic and a cronjob to handle the rules to update with the dynamic WAN IPs
  • Deploy and test

What we need

  • Linux VM (Ubuntu, Hardened BSD, etc)
  • Docker and Docker Compose
  • Dynamic DNS service to track the changing IP (Dyndns,no-Ip, etc)


Setup Dynamic DNS solution to track your Dynamic WAN IP

for this demo, we are going to use DynDNS since I already own a paid account and its supported on most platforms (Routers, UTMs, NAS devices, IP camera-DVRs, etc)

Use some google-fu there are multiple ways to do this without having to pay for the service, all we need is a DNS record that's up-to-date with your current Public IP address. 

For Network A and Network B, I’m going to use the routers built-in DDNS update features

Network A gateway – UDM Pro

Network B Gateway – Netgear R6230


Setup the VM with Docker-compose

Pick your service provider, you can and should be able to use a free tier VM for this since its just DNS

  • Linode
  • AWS lightsail
  • IBM cloud
  • Oracle cloud
  • Google Compute
  • Digital Ocean droplet

Make sure you have a dedicated (static) IPv4 and IPv6 address attached to the resource

For this deployment, I’m going to use a Linode – Nanode, due to their native IPv6 support and cause I prefer their platform for personal projects

Setup your Linode VM – Getting started Guide

SSH in to the VM or use weblish console

Update your packages and sources

sudo apt-get update 
install Docker and Docker Compose

Assuming you already have SSH access to the VM with a static IPv4 and IPv6 address

Guide to installing Docker Engine on Ubuntu

Guide to Installing Docker-Compose

Once you have this setup confirm the docker setup

docker-compose version

Setup the Pi-hole Docker Image

Lets Configure the docker networking side to fit our Needs

Create a Seperate Bridge network for the Pi-hole container

I guess you could use the default bridge network, but I like to create one to keep things organized and this way this service can be isolated from the other containers I have

docker network create --ipv6 --driver bridge --subnet "fd01::/64" Piholev6


We will use this network later in docker compose

With the new ubuntu version 20.x, Systemd will start a local DNS stub client that runs on

which will prevent the container from starting. because Pi-hole binds to the same port UDP 53

we could disable the service but that breaks DNS resolution on the VM causing more headaches and pain for automation and updates

After some google fu and trickering around this this is the workaround i found.

  • Disable the stub-listener
  • Change the symlink to the /etc/resolved.conf to /run/systemd/resolve/resolv.conf
  • push the external name servers so the VM won’t look at loopback to resolve DNS
  • Restart systemd-resolved
Resolving Conflicts with the systemd-resolved stub listener

We need to disable the stub listener thats bound to port 53, as i mentioned before this breaks the local dns resolution we will fix it in a bit.

sudo nano /etc/systemd/resolved.conf

Find and uncomment the line “DNSStubListener=yes” and change it to “no”

After this we need to push the external DNS servers to the box, this setting is stored on the following file

# is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.


But we cant manually update this file with out own DNS servers, lets investigate

Cartoon of a detective investigate following footprints | Premium ...
ls -l /etc/resolv.conf

its a symlink to the another system file


When you take a look at the directory where that file resides, there are two files

When you look at the other file you will see that /run/systemd/resolve/resolv.conf is the one which really is carrying the external name servers

You still can’t manually edit This file, and it gets updated by whatever the IPs provided as DNS servers via DHCP. netplan will dictate the IPs based on the static DNS servers you configure on Netplan YAML file

i can see there two entries, and they are the default Linode DNS servers discovered via DHCP, I’m going to keep them as is, since they are good enough for my use case

If you want to use your own servers here – Follow this guide

 Lets change the symlink to this file instead of the stub-resolve.conf

$ sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

Now that its pointing to the right file

Lets restart the systemd-resolved

systemctl restart systemd-resolved

Now you can resolve DNS and install packages, etc

Docker compose script file for the PI-Hole

sudo mkdir /Docker_Images/
sudo mkdir /Docker_Images/Piholev6/

Lets navigate to this directory and start setting up our environment

nano /Docker_Images/Piholev6/docker-compose.yml
version: '3.4'

    container_name: pihole_v6
    image: pihole/pihole:latest
    hostname: Multicastbits-DNSService
      - "53:53/tcp"
      - "53:53/udp"
      - "8080:80/tcp"
      - "4343:443/tcp"
      TZ: America/New_York
      WEBPASSWORD: F1ghtm4_Keng3n4sura
      enable_ipv6: "true"
      ServerIPv6: 2600:3c03::f03c:92ff:feb9:ea9c
       - '${ROOT}/pihole/etc-pihole/:/etc/pihole/'
       - '${ROOT}/pihole/etc-dnsmasq.d/:/etc/dnsmasq.d/'
      - NET_ADMIN
    restart: always

      name: Piholev6
      name: Piholev6

Lets break this down a littlebit

  • Version – Declare Docker compose version
  • container_name – This is the name of the container on the docker container registry
  • image – What image to pull from the Docker Hub
  • hostname – This is the host-name for the Docker container – this name will show up on your lookup when you are using this Pi-hole
  • ports – What ports should be NATed via the Docker Bridge to the host VM
  • TZ – Time Zone
  • DNS1 – DNS server used with in the image
  • DNS2 – DNS server used with in the image
  • WEBPASSWORD – Password for the Pi-Hole web console
  • ServerIP – Use the IPv4 address assigned to the VMs network interface(You need this for the Pi-Hole to respond on the IP for DNS queries)
  • IPv6 – Enable Disable IPv6 support
  • ServerIPv6 – Use the IPv4 address assigned to the VMs network interface (You need this for the Pi-Hole to respond on the IP for DNS queries)
  • volumes – These volumes will hold the configuration data so the container settings and historical data will persist reboots
  • cap_add:- NET_ADMIN – Add Linux capabilities to edit the network stack – link
  • restart: always – This will make sure the container gets restarted every time the VM boots up – Link
  • networks:default:external:name: Piholev6 – Set the container to use the network bridge we created before

Now lets bring up the Docker container

docker-compose up -d

-d switch will bring up the Docker container in the background

Run ‘Docker ps’ to confirm

Now you can access the web interface and use the Pihole

verifying its using the bridge network you created

Grab the network ID for the bridge network we create before and use the inspect switch to check the config

docker network ls
docker network inspect f7ba28db09ae

This will bring up the full configuration for the Linux bridge we created and the containers attached to the bridge will be visible under the “Containers”: tag


I manually configured my workstations primary DNS to the Pi-Hole IPs

Updating the docker Image

Pull the new image from the Registry

docker pull pihole/pihole

Take down the current container

docker-compose down

Run the new container

docker-compose up -d

Your settings will persist this update

Securing the install

now that we have a working Pi-Hole with IPv6 enabled, we can login and configure the Pihole server and resolve DNS as needed

but this is open to the public internet and will fall victim to DNS reflection attacks, etc

lets set up firewall rules and open up relevant ports (DNS, SSH, HTTPS) to the relevant IP addresses before we proceed

Disable IPtables from the docker daemon

Ubuntu uses UFW (uncomplicated firewall) as an obfuscation layer to make things easier for operators, but by default, Docker will open ports using IPtables with higher precedence, Rules added via UFW doesn’t take effect

So we need to tell docker not to do this when launching a container so we can manage the firewall rules via UFW

This file may not exist already if so nano will create it for you

sudo nano /etc/docker/daemon.json

Add the following lines to the file

"iptables": false

restart the docker services

sudo systemctl restart docker

now doing this might disrupt communication with the container until we allow them back in using UFW commands, so keep that in mind.

Automatically updating Firewall Rules based on the DYN DNS Host records

we are going to create a shell script and run it every hour using crontab

Shell Script Dry run

  • Get the IP from the DYNDNS Host records
  • remove/Cleanup existing rules
  • Add Default deny Rules
  • Add allow rules using the resolved IPs as the source

Dynamic IP addresses are updated on the following DNS records


Lets start by creating the script file under /bin/*

sudo touch /bin/
sudo chmod +x /bin/
sudo nano /bin/

now lets build the script

now=$(date +"%m/%d/%T")
#Get the network IP using dig
Network01_CurrentIP=`dig +short $DYNDNSNetwork01`
Network02_CurrentIP=`dig +short $DYNDNSNetwork02`
echo "-----------------------------------------------------------------"
echo Network A WAN IP $Network01_CurrentIP
echo Network B WAN IP $Network02_CurrentIP
echo "Script Run time : $now"
echo "-----------------------------------------------------------------"
#update firewall Rules
#reset firewall rules
sudo ufw --force reset
#Re-enable Firewall
sudo ufw --force enable
#Enable inbound default Deny firewall Rules
sudo ufw default deny incoming
#add allow Rules to the relevant networks
sudo ufw allow from $Network01_CurrentIP to any port 22 proto tcp
sudo ufw allow from $Network01_CurrentIP to any port 8080 proto tcp
sudo ufw allow from $Network01_CurrentIP to any port 53 proto udp
sudo ufw allow from $Network02_CurrentIP to any port 53 proto udp
#add the ipV6 DNS allow all Rule - Working on finding an effective way to lock this down, with IPv6 rick is minimal
sudo ufw allow 53/udp
#find and delete the allow any to any IPv4 Rule for port 53
sudo ufw --force delete $(ufw status numbered | grep '53*.*Anywhere.' | grep -v v6 | awk -F"[][]" '{print $2}')
echo "--------------------end Script------------------------------"

Lets run the script to make sure its working

I used a online port scanner to confirm

Setup Scheduled job with logging

lets use crontab and setup a scheduled job to run this script every hour

Make sure the script is copied to the /bin folder with the executable permissions

using crontab -e (If you are launching this for the first time it will ask you to pick the editor, I picked Nano)

crontab -e

Add the following line

0 * * * * /bin/ >> /var/log/PIHolefwruleupdate_Cronoutput.log 2>&1
Lets break this down
0 * * * *

this will run the script every time minutes hit zero which is usually every hour


Script Path to execute

/var/log/PIHolefwruleupdate_Cronoutput.log 2>&1

Log file with errors captured