hi friends,
i have installed a REDHAT Cent os on my server.
There are few users which have ssh,sftp,telnet login access to this server.now i want to create a new user such that he can only be able to do sftp login to this server and not ssh telnet etc.
Will you please help me in this problem?

set his shell to /bin/false or /bin/nologin either directly in /etc/passwd or use the usermod tool. ftp doesn't spawn a user shell, so will still work, but ssh itself will die instantly.

Here's another way if your system supports PAM (which it does) using Scponly and PAM_listfile. I use this because it allows for more granular control.
- Install scponly,
- Add scponly to /etc/shells,
- "vipw" and change shell to /usr/bin/scponly.

Now the trick is if you chose Vsftpd as your FTP daemon you already have /etc/pam/d/vsftpd and you already have within that PAM stack file a line "auth required pam_listfile.so item=user sense=deny file=/etc/vsftpd.ftpusers onerr=succeed". Basically we'll add similar to any service we want to deny logins for.

- Add user to Vsftpd denied list (sense=deny): "echo $deniedusername >> /etc/vsftpd.ftpusers",
- Make the ACL: "echo $deniedusername > /etc/login.deny" (change $deniedusername),
- Add this line: "auth required pam_listfile.so item=user sense=deny file=/etc/login.deny onerr=succeed" to all services you want to deny user access for like login, ftp, telnet etc, etc. Don't add it to system-auth or you'll block about every access for the user (which is neat too but not the point here).

Now watch your messages/secure logs and test. If you ftp in as the user you should be blocked. If you "ssh user@host 'touch test'" this will fail. If you ssh in as the user you can't get a commandline. Etc, etc.