Harden SSH on RHEL 9

Back up config

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

Key settings (/etc/ssh/sshd_config)

Port 2222
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
AllowUsers deploy alice
Protocol 2
ClientAliveInterval 600
ClientAliveCountMax 0
X11Forwa...

Harden SSH on Ubuntu 24.04

Back up config

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

Key settings (/etc/ssh/sshd_config)

Port 2222
PermitRootLogin no
PasswordAuthentication no
PubkeyAuthentication yes
AllowUsers deploy alice
Protocol 2
ClientAliveInterval 600
ClientAliveCountMax 0
X1...

Install and Configure Postfix on AlmaLinux 9

Step 1 – Install

dnf install -y postfix mailx
systemctl enable --now postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination =...

Install and Configure Postfix on Arch Linux

Step 1 – Install

pacman -S --noconfirm postfix
systemctl enable --now postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination =...

Install and Configure Postfix on Debian 12

Step 1 – Install

DEBIAN_FRONTEND=noninteractive apt install -y postfix
systemctl enable --now postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocol...

Install and Configure Postfix on Gentoo Linux

Step 1 – Install

emerge --ask mail-mta/postfix
rc-update add postfix default && rc-service postfix start

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_pr...

Install and Configure Postfix on NetBSD 10

Step 1 – Install

pkgin install postfix
echo 'postfix=YES' >> /etc/rc.conf && service postfix start

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocols =...

Install and Configure Postfix on OpenBSD 7.5

Step 1 – Install

pkg_add postfix
rcctl enable postfix && rcctl start postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination =...

Install and Configure Postfix on RHEL 9

Step 1 – Install

dnf install -y postfix mailx
systemctl enable --now postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination = $myh...

Install and Configure Postfix on Ubuntu 24.04

Step 1 – Install

DEBIAN_FRONTEND=noninteractive apt install -y postfix
systemctl enable --now postfix

Step 2 – /etc/postfix/main.cf

myhostname  = mail.example.com
mydomain    = example.com
myorigin    = $mydomain
inet_interfaces = all
inet_proto...

Install Apache HTTP Server on AlmaLinux 9

Step 1 – Install

dnf install epel-release -y
dnf install -y httpd mod_ssl
systemctl enable --now httpd

Step 2 – Open firewall ports

firewall-cmd --permanent --add-service=http
firewall-cmd --permanent --add-service=https
firewall-cmd --reload

Step

Install Apache HTTP Server on Arch Linux

Step 1 – Install

pacman -Syu --noconfirm
pacman -S --noconfirm apache
systemctl enable --now httpd

Step 2 – Open firewall ports

ufw allow 80/tcp && ufw allow 443/tcp && ufw reload

Step 3 – Verify

curl -I http://localhost
apachectl -v

Main config...

Install Apache HTTP Server on Debian 12

Step 1 – Install

apt update && apt upgrade -y
apt install -y apache2
systemctl enable --now apache2

Step 2 – Open firewall ports

ufw allow 'Apache Full'
ufw reload

Step 3 – Verify

curl -I http://localhost
apachectl -v

Main config: /etc/apache2/a...

Install Apache HTTP Server on Gentoo Linux

Step 1 – Install

emerge --sync
emerge --ask www-servers/apache
rc-update add apache2 default
rc-service apache2 start

Step 2 – Open firewall ports

iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j ACCEPT

Step 3

Install Apache HTTP Server on NetBSD 10

Step 1 – Install

pkgin update
pkgin install apache24
echo 'apache=YES' >> /etc/rc.conf
service apache start

Step 2 – Open firewall ports

# configure NPF for ports 80 and 443

Step 3 – Verify

curl -I http://localhost
apachectl -v

Main config: /usr...

Install Apache HTTP Server on OpenBSD 7.5

Step 1 – Install

pkg_add apache-httpd
rcctl enable apache2
rcctl start apache2

Step 2 – Open firewall ports

# /etc/pf.conf: pass in on egress proto tcp to port { 80 443 }
pfctl -f /etc/pf.conf

Step 3 – Verify

curl -I http://localhost
apachectl -v...

Install Apache HTTP Server on RHEL 9

Step 1 – Install

subscription-manager repos --enable codeready-builder-for-rhel-9-$(arch)-rpms
dnf install -y httpd mod_ssl
systemctl enable --now httpd

Step 2 – Open firewall ports

firewall-cmd --permanent --add-service=http
firewall-cmd --permanent --ad...

Install Apache HTTP Server on Ubuntu 24.04

Step 1 – Install

apt update && apt upgrade -y
apt install -y apache2
systemctl enable --now apache2

Step 2 – Open firewall ports

ufw allow 'Apache Full'
ufw reload

Step 3 – Verify

curl -I http://localhost
apachectl -v

Main config: /etc/apache...

Install Docker on AlmaLinux 9

Step 1 – Install

dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
dnf install -y docker-ce docker-ce-cli containerd.io docker-compose-plugin
systemctl enable --now docker

Step 2 – Add user to docker group

usermod -aG docker $...

Install Docker on Arch Linux

Step 1 – Install

pacman -S --noconfirm docker docker-compose
systemctl enable --now docker

Step 2 – Add user to docker group

usermod -aG docker $USER && newgrp docker

Step 3 – Verify

docker --version
docker run --rm hello-world

Step 4 – Example compose.yml

Install Docker on Debian 12

Step 1 – Install

install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/$(. /etc/os-release && echo "$ID")/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg
chmod a+r /etc/apt/keyrings/docker.gpg
echo "deb [arch=$(dpkg --print-architecture...

Install Docker on Gentoo Linux

Step 1 – Install

emerge --ask app-containers/docker app-containers/docker-cli
rc-update add docker default && rc-service docker start

Step 2 – Add user to docker group

usermod -aG docker $USER && newgrp docker

Step 3 – Verify

docker --version
docker run --r...

Install Docker on NetBSD 10

Step 1 – Install

# Docker is not natively available on NetBSD 10.
# Consider running a Linux VM or using podman.

Step 2 – Add user to docker group

usermod -aG docker $USER && newgrp docker

Step 3 – Verify

docker --version
docker run --rm hello-world

Step 4 –

Install Docker on OpenBSD 7.5

Step 1 – Install

# Docker is not natively available on OpenBSD 7.5.
# Consider running a Linux VM or using podman.

Step 2 – Add user to docker group

usermod -aG docker $USER && newgrp docker

Step 3 – Verify

docker --version
docker run --rm hello-world

Step