See user

how i can see the user list in redhat 6

If you're using local authentication, simply type:
cat /etc/passwd

That lists the accounts set up in the system. Not all of them are user accounts though.

The first column is login name, second is x, third is user ID, 4th is group ID, 5th in user name, 6th is user's home directory, 7th field is the shell program preference of the user. Type man 5 passwd to get the meanings of the various fields.

Generally, users who are real users (and not just accounts used by daemons) are usually set up with user IDs >= 1000. Another thing that real users use a real command shell like /bin/bash, whereas daemon accounts generally use /bin/false or /sbin/nologin. However, some daemon accounts do use /bin/sh as the shell. Most of these will have user ID < 1000 and the user name generally describes which daemon uses the login.

Hope this helps.

What is nobody? (user name)
What is login name of Debian-ipw3945d, but no user name? Must be a daemon, eh?
same for Debian-exim
What is sys? (user name)

nobody is an unprivileged account that was historically used by many server daemons (such as apache, ftp, postfix, exim etc.) to run as the nobody user. The trouble with this approach is that a person who manages to own one daemon could also own the other daemons, because they are all running as the same user ID. Which is why these days, most daemons use separate user IDs to run under (e.g. apache is setup to run as www or www-user in many distros, exim runs as exim4 or debian-exim and so on). However, the nobody user is retained for historical reasons, just in case there is some really old code that is still set to run as the nobody user.