Running a bash script as root on boot

Question

i have a script that calculate an ip address (using gateway address) than change,

the script work when i launch it manually with sudo

sudo ./changework.sh 

i want this script to run during bootup time

i

sudo cp changework.sh /etc/init.d/changework sudo chmod+x /etc/init.d/changework sudo update-rc.d changework defaults 

but it does not work,

also i tested it using

sudo crontab -e 

then added

@reboot sleep 10 && /home/ubunu/changework.sh 

it does not work either

changework.sh

#!/bin/bash #set interface interface="enp0s5" #read current IP address on interface current_ip=`ifconfig $interface 2>/dev/null|awk '/inet addr:/ {print $3}'|sed 's/Bcast://'` IP=`cut -f1,2,3 -d"." <<< $current_ip` lIP=`cut -f4 -d"." <<< $current_ip` lIP=`expr $lIP - 34` IP=$IP"."$lIP #return default gateway gateway=$(/sbin/ip route | awk '/default/ { print $3 }') #check if IP is taken using ping count=`ping -c 1 $IP | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }'` if [ $count -eq 0 ]; then #change IP if available ifconfig $interface down ifconfig $interface $IP up ifconfig $interface #change gateway ip route add default via $gateway else #IP change not possible echo "IP not available" fi 

would any one please have a solution or a workaround and thanks for any help or suggestion

Answer 1

If you are on a jessie (or latter) i would suggest to follow this nice guide, since the it uses systemd approach.

Answer 2

• Don't use sudo if you are already root. And the only way to execute a script at system startup is being root.

• Why all the copying the file into /etc/init.d? Copy it there once and keept it there. Then execute it from there. - Or go with a script being called from systemd as proposed by Sandro B.

• Don't use commands only. Always give the full path. Especially at bootup and in cronjobs. E.g.: ifconfig is /sbin/ifconfig

• You want to use "/bin/ip" instead of "ifconfig". The latter is outdated.

• Why don't you use /etc/network/interfaces and /etc/network/interfaces.d ? (man interfaces) . Especially "pre-up" to make sure that the script is always executed before the interface is up.

• If I get your intention right you want to use a dhcp server in your network. What would happen if the first IP you give to your server is already in use?

Answer 3

i changed my code

#!/bin/bash # /etc/init.d/changework #set interface interface="eth1" #read current IP address on interface current_ip=`/sbin/ifconfig $interface 2>/dev/null|awk '/inet addr:/ {print $3}'|sed 's/Bcast://'` IP=`cut -f1,2,3 -d"." <<< $current_ip` lIP=`cut -f4 -d"." <<< $current_ip` lIP=`expr $lIP - 34` IP=$IP"."$lIP #return default gateway gateway=$(/sbin/ip route | awk '/default/ { print $3 }') #check if IP is taken using ping count=`/bin/ping -c 1 $IP | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }'` if [ $count -eq 0 ]; then #change IP if available /sbin/ifconfig $interface down /sbin/ifconfig $interface $IP up /sbin/ifconfig $interface #change gateway /bin/ip route add default via $gateway else #IP change not possible echo "IP not available" fi 

then

sudo crontab -e

and added

SHELL=/bin/bash

@reboot sleep 10 && /home/ubunu/changework.sh

but nothing any help please

Answer 4

i ended up doing changing the content of rc.local, and like @user2563336 we don't need root access because login script have root access

#!/bin/bash # # rc.local # # This script is executed at the end of each multiuser runlevel. # Make sure that the script will "exit 0" on success or any other # value on error. # # In order to enable or disable this script just change the execution # bits. # # By default this script does nothing. writeinterfacefile() { cat << EOF > $1 # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface allow-hotplug eth0 iface eth0 inet static address $2 #network 192.168.1.0 netmask $3 #broadcast 192.168.1.255 gateway $4 dns-nameservers 8.8.8.8 EOF #don't use any space before of after 'EOF' in the previous line } file="/etc/network/interfaces" current_ip=`sudo ifconfig eth0 2>/dev/null|awk '/inet addr:/ {print $3}'|sed 's/Bcast://'` IP=`cut -f1,2,3 -d"." <<< $current_ip` lIP=`cut -f4 -d"." <<< $current_ip` lIP=`expr $lIP - 36` ip=$IP"."$lIP mask=`sudo ifconfig eth0 2>/dev/null|awk '/inet addr:/ {print $4}'|sed 's/Mash://'` mask=`cut -f2 -d":" <<< $mask` gateway=$(/sbin/ip route | awk '/default/ { print $3 }') #/bin/rm $file /bin/mv $file /etc/network/BAKinterfaces /usr/bin/touch $file writeinterfacefile $file $ip $mask $gateway /etc/init.d/networking restart exit 0