Tips Linux Dhclient Dynamic Mount Point

#!/bin/sh
    # Filename:     /etc/dhcp/dhclient-exit-hooks.d/mount_var_diskless
    # Purpose:      Used by dhclient-script to set mount HADES's var/diskless filesystem 
    #               from either the local net (preferred) or the GSI network
    #
    
    # Do not update hostname for virtual machine IP assignments
    if [ "$interface" != "eth0" ] && [ "$interface" != "eth1" ] && [ "$interface" != "wlan0" ]
    then
        return
    fi
    
    if [ "$reason" != BOUND ] && [ "$reason" != RENEW ] && [ "$reason" != REBIND ] && [ "$reason" != REBOOT ]
    then
            return
    fi
    
    var_diskless_hades=192.168.100.50
    var_diskless_gsi=140.181.75.158 
    var_diskless_path=/var/diskless/dreamplug
    var_diskless_mount=/var/diskless/dreamplug
    
    echo dhclient-exit-hooks.d/mount_var_diskless: new domain-name-servers: $new_domain_name_servers 
    
    echo "$new_domain_name_servers" | grep -q $var_diskless_hades && var_diskless_addr=$var_diskless_hades || var_diskless_addr=$var_diskless_gsi
    
    #clean up, but only different mounts
    grep -v "$var_diskless_addr:$var_diskless_path" /etc/mtab | grep -q "$var_diskless_mount" && umount $var_diskless_mount 
    
    #mount
    [ -d "$var_diskless_mount" ] || mkdir -p $var_diskless_mount
    grep "$var_diskless_addr:$var_diskless_path" /etc/mtab | grep -q "$var_diskless_mount" || mount $var_diskless_addr:$var_diskless_path $var_diskless_mount
    
    echo dhclient-exit-hooks.d/mount_var_diskless: mounted $var_diskless_addr:$var_diskless_path
    
    unset var_diskless_hades 
    unset var_diskless_gsi 
    unset var_diskless_path 
    unset var_diskless_mount