How to run a command when boots up?

(A) Execute command at system startup
Let us assume you would like to run command called

i) Create a script called in /etc/init.d/ directory(login as root)
# vi /etc/init.d/

ii) Add commands to this script one by one:
echo “Setting up customized environment…”

iii) Setup executable permission on script:
# chmod +x /etc/init.d/

iv)Make sure this script get executed every time Debian Linux system boot up/comes up:
# update-rc.d defaults 100

Where, Your startup script name
defaults : The argument ‘defaults’ refers to the default runlevels, which are 2 through 5.
100 : Number 100 means script will get executed before any script containing number 101. Just run the command ls –l /etc/rc3.d/ and you will see all script soft linked to /etc/init.d with numbers.

Next time you reboot the system, you custom command or script will get executed via You can add more commands to this file or even call other shell/perl scripts from this file too.

(B) Execute shell script at system startup
Open the file in /etc/init.d/ directory
# vi /etc/init.d/

Append your script path to the end as follows (suppose your script is /root/fw.start – script that starts firewall)


Save the file.