Where we have to specify the startup scripts on reboot?

lsblk 

to view the number of disks.

/etc/rc.local    (not recommended )

Most of the startup scripts are in this directories:

/etc/init.d      

/etc/rc.d

/etc/rc.d/rc5.d

/etc/rc.d/rc3.d

Inside the  rc3.d  and the  rc5.d:

(we will be having the startup scripts and the stop scripts for each and every service, for some services, we have only startup scripts).

In the permissions row, we you see l  (L) in the beginning :

that is the link, that means that file is the link:

lrwxrwxrwx.  1 root root   31 May 14  2012 S74xinetd -> ../init.d/xinetd

S  —>  startup scripts 

lrwxrwxrwx.  1 root root   27 May 15  2013 K88htcacheclean -> ../init.d/htcacheclean

K —>  stop scripts (works during shutdown).

/etc/rc.d/rc6.d

lrwxrwxrwx.  1 root root   21 May 11  2015 K35httpd -> ../init.d/httpd

k   —>  stop scripts.