Centos7升级ssh

1、备份原有文件

mkdir ssh.bak
cp /etc/ssh/* /etc/ssh.bak

2、安装并启动Telnet

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

//设置开机自启动
systemctl enable telnet.socket
systemctl enable xinetd

//添加Telnet配置文件
vi /etc/xinetd.d/telnet

//添加下列语句
# default: on
# description: The telnet server serves telnet sessions; it uses \
#    unencrypted username/password pairs for authentication.
service telnet
{
    flags        = REUSE
    socket_type    = stream        
    wait        = no
    user        = root
    server        = /usr/sbin/in.telnetd
    log_on_failure    += USERID
    disable        = no		//默认为yes时，不允许root登录
}

vi /etc/securetty
//添加下列语句,允许远程设备使用root账号登录
pts/0
pts/1

3、卸载旧版本ssh（Telnet登录）

systemctl stop sshd

//查询已安装的openssh包
rpm -qa | grep openssh
//结果
openssh-server-7.4p1-16.el7.x86_64
openssh-clients-7.4p1-16.el7.x86_64
openssh-7.4p1-16.el7.x86_64
//卸载
rpm -e openssh* --nodeps

//删除配置文件
rm -rf /etc/ssh/*

4、安装ssh

上传ssh安装包并解压到/usr/local/openssh目录

tar -zxvf /usr/local/openssh/openssh-8.3p1.tar.gz

安装依赖包

yum install -y gcc openssl-devel pam-devel rpm-build

编译安装，在/usr/local/openssh/openssh-8.3p1目录下执行

./configure --prefix=/usr --sysconfdir=/etc/ssh  --with-pam  --with-zlib  --with-md5-passwords
make
make install

5、修改配置

修改配置文件

vi /etc/ssh/sshd_config

//取消下列行注释，若无则添加
PermitRootLogin yes
PubkeyAuthentication yes
PasswordAuthentication yes

复制启动文件到/etc/rc.d/init.d/sshd

cp /usr/local/openssh/openssh-8.3p1/contrib/redhat/sshd.init /etc/rc.d/init.d/sshd

启动sshd服务

service sshd start		//先用service命令启动后才可使用systemctl命令
ssh -V		//查看ssh版本
chkconfig sshd on		//设置开机启动