cleaned up(?) script for rhel

05-hostname.rhel

#!/bin/bash

CONFIG_FILE="/etc/sysconfig/network"

function set_hostname() {
    NAME=$1

    [ -n "$NAME" ] || exit 0

    sed -i '/^HOSTNAME=.*$/d' $CONFIG_FILE
    echo "HOSTNAME=$NAME" >> $CONFIG_FILE

    hostname $OS_HOST_NAME
}

function get_dns_name() {
    first_ip=$(hostname -I | cut -d' ' -f1)
    text=$(host $first_ip)
    [ $? = 0 ] || exit 0
    [[ $text == *"has no PTR record" ]] && exit 0
    name=$(echo "$text" | awk '{print $(NF)}' | sed 's/\.$//')
    echo $name
}

function split_name() {
    OS_HOST_NAME=$( echo $FOUND_NAME | cut -f1 -d\. )
    DOMAIN=$( echo $FOUND_NAME | cut -f2- -d\. )
    export OS_HOST_NAME DOMAIN
}

function set_hosts_entry() {
    # eth0 should always be assigned
    # so we'll use it's IP for the main hosts entry
    if [[ -z ${ETH0_IP} ]]; then
      return 1
    else
      hosts_entry="${ETH0_IP}       ${FOUND_NAME} ${OS_HOST_NAME}"
    fi

    # do nothing if entry is as expected
    if grep -q "$hosts_entry" /etc/hosts ; then 
      return 0
    fi

    # modify the actual entry for this host, ensure ip and host are OK
    if grep -v ^# /etc/hosts | grep -v 127.0 | grep -q ${OS_HOST_NAME} ; then
       sed -i \
       "s/.*${OS_HOST_NAME}.*/${hosts_entry}/" \
       /etc/hosts
    else 
      echo $hosts_entry >> /etc/hosts
    fi
}

function set_resolv_entry() {
# add the domain to resolver's infos, this allows for proper resolution
   if ! grep -q -E "^domain.*$DOMAIN" /etc/resolv.conf ; then
     echo "domain $DOMAIN" >> /etc/resolv.conf
   fi

}

#get_name() {
# hostname could've been passed in via variables
    if [ -n "$SET_HOSTNAME" ]; then
        FOUND_NAME=${SET_HOSTNAME}
# or be derived from DNS
    elif [ -n "$DNS_HOSTNAME" ]; then
        FOUND_NAME=$(get_dns_name)
    else
# or missing
        exit 1
    fi
    export FOUND_NAME
#}


# get_name               &&
split_name $FOUND_NAME   &&
set_hostname $FOUND_NAME &&
set_resolv_entry         &&
set_hosts_entry