Password on run-level 1
 

hello..
how to set password on runlevel 1.

Note that the "run level" concept is depreciated, and, basically, obsolete in distributions using systemd. What distribution are you using?

i am using RHEL6 and RHEL 5.4 server edition..

Its just
assuming you're logged in as root. To change root's passwd, you can skip specifying the root username.

i m asking for init S or init 1 not for init 5.
when we boot our linux os we can place bootloader password but i wan t to give password on init 1(run level 1) so no one can enter or get access in runlevel 1..

...which you can't, since runlevel 1 is only single user for maintenance/rescue purposes. And even if you could, it's pointless, since someone can just boot the system with a CD/DVD/USB drive, mount the drive from there, and remove the password from the shadow file.

As above
the boot password is almost as useless
with the exception of on say a laptop
your "normal below average" thief will not know how to bypass it
( unless they can use google)