lint-hostname

#which ifconfig &>dev/null && IP=$(ifconfig | grep "^.*inet" |awk '{print $2}' |head -1)
#dnsdomainname can be as domain in resolv.conf depending on nsswitch.conf
IP=$(hostname -I|awk '{print $1}'|head -1)
FQDN=$(host $IP |awk '{print $NF}' | sed s,.$,,)
HS=$(hostname -s)
HF=$(hostname -f)
EH=$(cat /etc/hostname)
DOMAIN=$(hostname -d)

echo "hostname -s     $HS"
echo "hostname -f     $HF"
echo "/etc/hostname   $EH"
echo "dnsdomainname   $DOMAIN"
echo "IP              $IP"
echo "DNS             $FQDN"
echo
if [ ! $HS = $EH ]; then echo hostname -s does not match /etc/hostname; fi
if [ ! $HF = $EH.$DOMAIN ]; then echo hostname -f does not match hostname -s with dnsdomainname attached; fi
if [ ! $FQDN = $HF ]; then echo DNS entry does not match hostname -f; fi
grep "$IP.*$FQDN.*$HS" /etc/hosts >/dev/null || echo "$IP\t$FQDN\t$HS entry not found in /etc/hosts"

# hostnamectl set-hostname whatever --static

# also check DNS with
# /etc/resolv.conf
# resolvectl
# systemctl status systemd-resolved

#host -t soa $DOMAIN
#host -t ns $DOMAIN
#host -t mx $DOMAIN
#host -a $DOMAIN