login to linux server hints

1. why we can not login in remote linux server using telnet?

When we login a server using telnet, there's a daemon process run named telnetd. The number of daemon process depends on the xinetd.conf, because telnetd all depend on xinetd(for Debian variant will be inetd).

cat /etc/xinetd.conf

# # Simple configuration file for xinetd

# # Some defaults, and include /etc/xinetd.d/

defaults {

instances = 60

log_type = SYSLOG

authpriv

log_on_success = HOST PID

log_on_failure = HOST

cps = 25 30

}

From this file, only 60 xinetd instances can be run at the same time. ftp and rlogin also depend on xinetd. So a server only afford very few logins for telnet.

ssh doesn't depend on xinetd, so if we use ssh protocol, you can always login to remote linux server(of course, now most linux server has supported openssh)