Dynamic hostname for VM’s generated from Virtualbox

I am currently working on dynamic environment provisioning for baremetal and hypervisors. Going through my notes, I found the following post, it was obviously copied from somewhere and i don’t have the URL for it. I am posting it here again for future reference as i think it is a very clever idea.

These scripts are used for simple management of hostnames for several VirtualBox VMs comprising a test or sandbox environment on your local machine.
Architecture:

• Each VM is configured to use bridged network adapter, so all VMs and the host can see each other
• A script is installed in each VM to run on post-ifup, which grabs VM’s IP, puts “$IP $desired-hostname $desired-fully-qualified-hostname” into /etc/hosts, changes hostname correspondingly, and puts VM’s hostname and fq-hostname into VM’s properties
• A script is used on the host machine, which loops through running VMs, and updates /etc/hosts on the host machine and on the VMs

Setup:

1. On CentOS/RedHat VM:
1.1. put “ifup-local.sh” to /etc/sysconfig/network-scripts directory
1.2. change HN and FQHN variable values to desired hostname and fully qualified hostname for this VM
1.3. make soft link to the file from /sbin: ln -s /etc/sysconfig/network-scripts/ifup-local.sh /sbin/ifup-local
2. On the host use update-vms script to update VMs and host’s /etc/hosts files when VMs are started, stopped, or network configuration (IPs) is updated

#!/bin/bash
# CentOS/RedHat neworking scripts call /sbin/ifup-local in the end of ifup-post. This script should be either put at /sbin/ifup-local, ore soft-linked

# desired hostname
HN=myhostname

# desired fully qualified hostname
FQHN=$HN.mydomain

# additional fully qualified hostnames
ALTHN="s1.$FQHN s2.$FQHN"

# get current IP address (assuming there is only one non-127.0.* network interface
IP_ADDR=$(/sbin/ifconfig eth0 2>&1 | grep 'inet addr:' | grep -v '127.0.' | cut -d: -f2 | awk '{ print $1}')

if [ -n "$IP_ADDR" ]
then
  # remove potentially existing old line from hosts
  grep -Ev " $FQHN\$" /etc/hosts | grep -Ev "$IP_ADDR " > /tmp/hosts
  # add new line to hosts
  echo -n "$IP_ADDR $FQHN" >> /tmp/hosts
  for s in "$ALTHN"
  do
echo -n " $s" >> /tmp/hosts
  done
echo " $HN" >> /tmp/hosts
  cp /tmp/hosts /etc/hosts
  # set hostname
  hostname $HN
  # set VirtualBox VM properties
  VBoxControl guestproperty set /VirtualBox/GuestInfo/Net/0/V4/HN $HN 2>&1 > /dev/nul
  VBoxControl guestproperty set /VirtualBox/GuestInfo/Net/0/V4/FQHN $FQHN 2>&1 > /dev/nul
  VBoxControl guestproperty set /VirtualBox/GuestInfo/Net/0/V4/ALTHN "$ALTHN" 2>&1 > /dev/nul
else
  # in case IP address was not found do nothing
  hostname localhost
fi

#!/bin/bash
# this script should be run on the VMs' host to synchronize all VMs' and the host's /etc/hosts files
# list all running VMs
VMS=$(VBoxManage list runningvms)

# create a base for VMs' /etc/hosts file
echo "127.0.0.1 localhost.localdomain localhost" > /tmp/vmhosts
echo "::1 localhost6.localdomain6 localhost6" >> /tmp/vmhosts
# here we will collect fq-hostnames of all VMs that have corresponding properties set
VMHNS=""
for VM in $VMS
do
  # VirtualBox lists VM names and UUIDs in its output; we are only interested in UUIDs
  if [[ "${VM:0:1}" == '{' ]]
  then
    # remove curly braces around VM UUID
    VM="${VM#\{}"
    VM="${VM%\}}"
    # get VM IP from VM's properties
    IP=$(VBoxManage guestproperty get $VM /VirtualBox/GuestInfo/Net/0/V4/IP | grep "Value: ")
    IP=${IP#Value\: }
    # get VM hostname from VM's properties
    HN=$(VBoxManage guestproperty get $VM /VirtualBox/GuestInfo/Net/0/V4/HN | grep "Value: ")
    HN=${HN#Value\: }
    # get VM fq-hostname from VM's properties
    FQHN=$(VBoxManage guestproperty get $VM /VirtualBox/GuestInfo/Net/0/V4/FQHN | grep "Value: ")
    FQHN=${FQHN#Value\: }
    # get VM fq-hostname from VM's properties
    ALTHN=$(VBoxManage guestproperty get $VM /VirtualBox/GuestInfo/Net/0/V4/ALTHN | grep "Value: ")
    ALTHN=${ALTHN#Value\: }
    if [[ -n "$VM" && -n "$IP" && -n "$HN" && -n "$FQHN" ]]
    then
echo "Processing VM $VM - $IP - $FQHN - $HN - $ALTHN"
      # remove potentially existing old record for this VM in host's /etc/hosts file
      grep -v "\(^\|[^a-zA-Z0-9\-\.]\)${FQHN//./\\.}\([^a-zA-Z0-9\-\.]\|$\)" /etc/hosts | grep -v "\(^\|[^a-zA-Z0-9\-\.]\)${HN//./\\.}\([^a-zA-Z0-9\-\.]\|$\)" | grep -v "\(^\|[^a-zA-Z0-9\-\.]\)${IP//./\\.}\([^a-zA-Z0-9\-\.]\|$\)" > /tmp/hosts
      # add a line for this VM to the file
      echo -n "$IP $FQHN" >> /tmp/hosts
      for s in "$ALTHN"
      do
echo -n " $s" >> /tmp/hosts
      done
echo " $HN" >> /tmp/hosts
      # update /etc/hosts file on the host (assuming that current user's password is in ~/Private/pwd file)
      sudo -S -p "" /bin/bash -c "cp /tmp/hosts /etc/hosts" < ~/Private/pwd       # add line for this VM to the VMs' /etc/hosts file       echo -n "$IP $FQHN" >> /tmp/vmhosts
      for s in "$ALTHN"
      do
echo -n " $s" >> /tmp/vmhosts
      done
echo " $HN" >> /tmp/vmhosts
      VMHNS="$VMHNS $FQHN"
    fi
fi
done

# get current host IP address and name (assuming there is only one non-127.0.* network interface)
HIP=$(/sbin/ifconfig 2>&1 | grep 'inet addr:' | grep -v '127.0.' | cut -d: -f2 | awk '{ print $1}')
HHN=$(hostname)
HFQHN=$(hostname -f)

# add a line for the host into /etc/hosts of all VMs
echo "$HIP $HHN $HFQHN" >> /tmp/vmhosts

# copy prepared VMs' /etc/hosts file to all VMs
if [ -n "$VMHNS" ]
then
for VMHN in $VMHNS
  do
scp -o NumberOfPasswordPrompts=0 -o StrictHostKeyChecking=no /tmp/vmhosts root@$VMHN:/etc/hosts
  done
fi