一、安装配置telnet

     [root@localhost ~]# yum -y install xinetd telnet-server

     [root@localhost ~]# cat > /etc/xinetd.d/telnet <<EOF

     service telnet {

    disable = no

    flags = REUSE

    socket_type = stream    

    wait = no

    user = root

    server = /usr/sbin/in.telnetd

    log_on_failure += USERID

    }

    EOF

    [root@localhost ~]# cat >> /etc/securetty <<EOF

    pts/0

    pts/1

    pts/2

    pts/3

    pts/4

    EOF

    [root@localhost ~]# systemctl enable xinetd --now

    [root@localhost ~]# systemctl enable telnet.socket --now

    [root@localhost ~]# ss -nltp | grep 23

    LISTEN     0      64        [::]:23                    [::]:*                   users:(("xinetd",pid=1744,fd=5))

二、安装openssh

[root@localhost ~]# yum remove openssh-server

[root@localhost ~]# yum -y install gcc gcc-c++ glibc make autoconf openssl openssl-devel pcre-devel pam-devel

[root@localhost openssh-8.8p1]# pwd

/tmp/openssh-8.8p1

[root@localhost openssh-8.8p1]# ./configure --prefix=/usr --sysconfdir=/etc/ssh --with-md5-passwords --with-pam

[root@localhost openssh-8.8p1]# echo $?

[root@localhost openssh-8.8p1]# make && make install

echo "UseDNS no" >> /etc/ssh/sshd_config

echo 'PermitRootLogin yes' >> /etc/ssh/sshd_config

echo 'PubkeyAuthentication yes' >> /etc/ssh/sshd_config

echo 'PasswordAuthentication yes' >> /etc/ssh/sshd_config

# if GUI

echo "X11Forwarding yes" >> /etc/ssh/sshd_config

echo "X11UseLocalhost no" >> /etc/ssh/sshd_config

echo "XAuthLocation /usr/bin/xauth" >> /etc/ssh/sshd_config

[root@localhost ssh]# ssh -V

OpenSSH_8.8p1, OpenSSL 1.0.2k-fips  26 Jan 2017

[root@localhost redhat]# pwd

/tmp/openssh-8.8p1/contrib/redhat

[root@localhost redhat]# ls

gnome-ssh-askpass.csh  gnome-ssh-askpass.sh  openssh.spec  sshd.init  sshd.pam

[root@localhost redhat]# cp -a sshd.init /etc/init.d/sshd

[root@localhost redhat]# cp -a sshd.pam /etc/pam.d/sshd.pam

[root@localhost redhat]# cd /etc/ssh

[root@ykt01 ssh]# chmod 600 ssh_host_ecdsa_key ssh_host_ed25519_key ssh_host_rsa_key

[root@localhost ~]# chkconfig --add sshd

[root@localhost ~]# systemctl enable sshd --now

# 切换ssh登陆

[root@localhost ~]# systemctl disable xinetd.service --now

[root@localhost ~]# systemctl disable telnet.socket --now