apt-get update; apt-get -y dist-upgrade; apt -y autoremove; apt clean; apt autoclean

root@gps1:~# cat /etc/apt/sources.list
deb http://approx.my.side/raspbian/ bullseye main contrib non-free rpi

apt clean; apt update; apt upgrade; apt dist-upgrade; apt autoremove

reboot

apt-get install snmpd
apt-get install lsof
Configure remote logging

ln -s /usr/share/zoneinfo/US/Central /etc/localtime

Set swap to 1G
vi /etc/dphys-swapfile
CONF_SWAPSIZE=1024
/etc/init.d/dphys-swapfile stop
/etc/init.d/dphys-swapfile start

/boot/cmdline.txt

dwc_otg.lpm_enable=0 console=tty1 root=PARTUUID=1d8091da-02 rootfstype=ext4 elevator=deadline fsck.repair=yes net.ifnames=0 rootwait


/boot/config.txt

#GPS Changes
enable_uart=1
init_uart_baud=57600
disable_pvt=1
dtoverlay=pps-gpio,gpiopin=21
dtoverlay=pi3-disable-bt


echo “pps-gpio” >> /etc/modules

apt-get install pps-tools

reboot

lsmod
vcgencmd measure_clock arm

apt-get install gpsd gpsd-clients

/etc/default/gpsd

DEVICES="/dev/gps0"
GPSD_OPTIONS="-n"
USBAUTO="false"



root@gps1:/etc/udev/rules.d# cat 09.gps.rules
KERNEL=="ttyAMA0", SYMLINK+="gps0"
KERNEL=="pps0", OWNER="root", GROUP="tty", MODE="0777", SYMLINK+="gpspps0"


systemctl enable gpsd

reboot

systemctl status gpsd
gpsmon /dev/gps0

ppstest /dev/pps0

reboot

systemctl disable systemd-resolved
systemctl stop systemd-resolved
systemctl status
systemctl disable dhcpcd.service
Configure /etc/network/interfaces

reboot (hope for the best)

apt-get install chrony

/etc/chrony/chrony.conf

# Source Clock
refclock PPS /dev/pps0 lock NMEA refid PPS1 prefer
refclock SHM 0 offset 0.5 refid NMEA noselect

# Internal peers
peer gps2.my.side iburst prefer

# Sanity Servers
server time1.google.com iburst
server time2.google.com iburst
server time3.google.com
server time4.google.com

# Act as an NTP server
allow XXX.XXX.XXX.XXX/XX

# Only allow chronyc from the localhost
cmdallow 127.0.0.1

# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift

# Allow the system clock to be stepped in the first three updates
# if its offset is larger than 1 second.
makestep 1.0 3

# Notify on error correction > 0.5 seconds
logchange 0.5

# Enable kernel synchronization of the real-time clock (RTC).
rtcsync

# Lock clock in to RAM
lock_all

# RTS
sched_priority 1

# Fudge Stratum if we cannot reach the internet
local stratum 10

# Get TAI-UTC offset and leap seconds from the system tz database.
leapsectz right/UTC
leapsecmode slew
maxslewrate 1000
smoothtime 400 0.001 leaponly

# Specify directory for log files.
logdir /var/log/chrony

# Select which information is logged.
log measurements statistics tracking

keyfile /etc/chrony/chrony.keys


systemctl enable chrony
systemctl status chrony
systemctl restart chrony
systemctl status chrony

watch “chronyc sources -v”

General OS Setup:
apt-get install libsasl2-modules postfix bsd-mailx deborphan
Create /root/.forward
/etc/postfix/main.cf: inet_interfaces = loopback-only

apt-get install bind9 dnsutils
named.conf.local

Fail2Ban
Install custom /etc/fail2ban/jail.local

apt-get install clamav
/etc/clamav/freshclam.conf
#NotifyClamd /etc/clamav/clamd.conf

Hits: 11