yum install -y telnet-server
yum install -y xinetd 
systemctl enable xinetd.service
systemctl enable telnet.socket
systemctl start telnet.socket
systemctl start xinetd

默認情況下，系統是不允許root用戶telnet遠程登錄的。如果要使用root用戶直接登錄，需設置如下內容:

echo ?‘pts/0‘ ?>>/etc/securetty
echo ‘pts/1‘ >>/etc/securetty
 

systemctl restart xinetd.service

然後在本地測試telnet能否連接到服務器 , 如果一直報密碼無效要註意selinux和防火墻
連接到的話就是如下顯示.輸入root密碼即可登錄

Kernel 3.10.0-514.el7.x86_64 on an x86_64
localhost login: root
Password:
Last login: Tue Nov 13 15:57:03 from 172.16.0.10
[root@localhost ~]#

二.升級開始:(註意 : 關閉SELinux)

先把openssh-7.9p1.tar.gz傳到服務器上 , 在進行升級的一系列操作.

1.yum安裝依賴
yum install -y gcc openssl openssl-devel pam-devel rpm-build pam-devel

2.卸載openssh

[root@localhost src]# rpm -qa | grep openssh
[root@localhost src]# rpm -e `rpm -qa | grep openssh` --nodeps
[root@localhost src]# rpm -qa | grep openssh

3.安裝openssh7.9
1)執行如下命令,設置適當的環境
(參考,包在這裏下載 http://www.linuxfromscratch.org/blfs/view/svn/postlfs/openssh.html )

[root@localhost src]# tar -zxvf openssh-7.9p1.tar.gz 
[root@localhost src]# cd openssh-7.9p1

3)安裝

[root@localhost src]# ./configure --prefix=/usr --sysconfdir=/etc/ssh --with-pam --with-zlib --with-md5-passwords --with-tcp-wrappers
[root@localhost src]#  make && make install

因為權限問題而報出警告

修改文件權限後再次執行make install

[root@localhost openssh-7.9p1]# chmod 600 /etc/ssh/ssh_host_rsa_key
[root@localhost openssh-7.9p1]# chmod 600 /etc/ssh/ssh_host_ecdsa_key
[root@localhost openssh-7.9p1]# chmod 600 /etc/ssh/ssh_host_ed25519_key
[root@localhost openssh-7.9p1]#  make install

4)執行如下命令
install -v -m755 contrib/ssh-copy-id /usr/bin && install -v -m644 contrib/ssh-copy-id.1 /usr/share/man/man1 && install -v -m755 -d /usr/share/doc/openssh-7.9p1 && install -v -m644 INSTALL LICENCE OVERVIEW README* /usr/share/doc/openssh-7.9p1

[root@localhost openssh-7.9p1]# ssh -V
OpenSSH_7.9p1, OpenSSL 1.0.2k-fips  26 Jan 2017

5)修改配置文件 PermitRootLogin yes 允許root遠程登錄 , 開機自啟

[root@localhost openssh-7.9p1]# echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
[root@localhost openssh-7.9p1]# cp -a contrib/redhat/sshd.init /etc/init.d/sshd
[root@localhost openssh-7.9p1]# chkconfig --add sshd
[root@localhost openssh-7.9p1]# chkconfig sshd on
[root@localhost openssh-7.9p1]# service sshd start
Starting sshd (via systemctl):                             [  OK  ]
[root@localhost openssh-7.9p1]# service sshd restart
Restarting sshd (via systemctl):                           [  OK  ]
[root@localhost openssh-7.9p1]# chkconfig --list sshd

4.把telnet關掉

[root@localhost openssh-7.9p1]# rpm -qa telnet-server
telnet-server-0.17-64.el7.x86_64
[root@localhost openssh-7.9p1]# systemctl stop telnet.socket 
[root@localhost openssh-7.9p1]# systemctl stop xinetd
[root@localhost openssh-7.9p1]# systemctl disable xinetd.service   
Removed symlink /etc/systemd/system/multi-user.target.wants/xinetd.service.
[root@localhost openssh-7.9p1]# systemctl disable telnet.socket
Removed symlink /etc/systemd/system/sockets.target.wants/telnet.socket.

linux openssh升級到7.9