Linux ssh命令详解

Posted 2020-12-02 ftl1012

  SSH(远程连接工具)连接原理：ssh服务是一个守护进程(demon)，系统后台监听客户端的连接，ssh服务端的进程名为sshd,负责实时监听客户端的请求(IP 22端口)，包括公共秘钥等交换等信息。

ssh服务端由2部分组成： openssh(提供ssh服务)    openssl(提供加密的程序)

ssh的客户端可以用 XSHELL，Securecrt, Mobaxterm等工具进行连接

ssh常见命令参数

usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec]
           [-D [bind_address:]port] [-e escape_char] [-F configfile]
           [-i identity_file] [-L [bind_address:]port:host:hostport]
           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]
           [-R [bind_address:]port:host:hostport] [-S ctl_path]
           [-W host:port] [-w local_tun[:remote_tun]]
           [[email protected]]hostname [command]

关于后台ssh服务的相关

# 查询openssl软件
	rpm -qa openssh openssl
# 查询sshd进程
	ps -ef | grep ssh
        --> /usr/sbin/sshd
# 查看ssh端口
	netstat -lntup | grep ssh   
	ss | grep ssh                (效果同上，同下，好用)
	netstat -a | grep ssh(记住这个)
	netstat -lnt | grep 22    ==>  查看22端口有没有开/ssh服务有没有开启
    技巧： netstat -lnt | grep ssh | wc -l -->只要大于2个就是ssh服务就是好的
# 查看ssh的秘钥目录
    ll /root/.ssh/known_hosts  # 当前用户家目录的.ssh目录下
# ssh的配置文件
	cat /etc/ssh/sshd_config 	
# ssh服务的关闭
	service sshd stop
# ssh服务的开启：
	service sshd start
# ssh服务的重启
	service sshd reload    [停止进程后重启] ==> 推荐
	service sshd restart   [干掉进程后重启] ==> 不推荐
# ssh远程登录
	ssh 192.168.1.100      # 默认利用当前宿主用户的用户名登录
	ssh [email protected]  # 利用远程机的用户登录
	ssh [email protected]  -o stricthostkeychecking=no # 首次登陆免输yes登录
	ssh [email protected] "ls /home/omc"  # 当前服务器A远程登录服务器B后执行某个命令
	ssh [email protected] -t "sh /home/omc/ftl.sh"  # 当前服务器A远程登录服务器B后执行某个脚本

 

ssh免密设置

1、进入用户的家目录

[[email protected] ~]# cd /root/.ssh/             【root用户就在root目录下的.ssh目录】
[[email protected] ~]# cd /home/omc/.ssh/   【普通用户就是在家目录下的.ssh目录】

2、根据DSA算法生成私钥和公钥【默认建立在当前用户的家目录】

 [[email protected] .ssh]# ssh-keygen -t dsa     # 一路回车即可
                 id_dsa         -->私钥(钥匙) 
                 id_dsa.pub     -->公钥(锁)

3.拷贝公钥给目标服务器

[[email protected] .ssh]# ssh-copy-id -i id_dsa.pub [email protected]              【 使用ssh登录的默认端口22】
[[email protected] .ssh]# ssh-copy-id -i id_dsa.pub –p 666 [email protected]   【使用ssh登录设置的端口666】

4. 查看目标服务器生成的文件

[[email protected] .ssh]$ ll /home/omc/.ssh/authorized_keys

5. 免密码登录目标服务器

ssh [email protected]  

6. 总结一下钥匙和锁的关系

1.多个钥匙开一把锁
      把id_dsa.pub 复制给各个服务器

2.一个钥匙开duobasuo
      把id_dsa 传给各个服务器
      把id_dsa 传给自己  

ssh排查问题

 1.判断物理链路是否通  ping 192.168.25.130     线路 | 防火墙 | 是否同一个网的
            ping   本身是icmp协议
2.判断服务是否正常      telnet 192.168.25.130 22
3.Linux防火墙          service iptables status ==>  /etc/init.d/iptables status

4.打开ssh的调测进行观察  ssh -vvv [email protected]

ssh的配置文件

/etc/ssh/sshd_config 

[[email protected] .ssh]# cat /etc/ssh/sshd_config 
#       $OpenBSD: sshd_config,v 1.80 2008/07/02 02:24:18 djm Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

# Disable legacy (protocol version 1) support in the server for new
# installations. In future the default will change to require explicit
# activation of protocol 1
Protocol 2

# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key

# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024

# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin yes
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#RSAAuthentication yes
#PubkeyAuthentication yes
#AuthorizedKeysFile     .ssh/authorized_keys
#AuthorizedKeysCommand none
#AuthorizedKeysCommandRunAs nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don‘t trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don‘t read the user‘s ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no
PasswordAuthentication yes

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
#KerberosUseKuserok yes

# GSSAPI options
#GSSAPIAuthentication no
GSSAPIAuthentication yes
#GSSAPICleanupCredentials yes
GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no

# Set this to ‘yes‘ to enable PAM authentication, account processing, 
# and session processing. If this is enabled, PAM authentication will 
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to ‘no‘.
#UsePAM no
UsePAM yes

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#ShowPatchLevel no
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10
#PermitTunnel no
#ChrootDirectory none

# no default banner path
#Banner none

# override default of no subsystems
Subsystem       sftp    /usr/libexec/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       ForceCommand cvs server

一般需啊哟修改ssh服务的启动文件sshd的几个点：
    1-1修改 /etc/ssh/sshd_config

  GSSAPIAuthentication yes    解决一台服务器管理多个ssh服务
        UseDNS no  加快响应速度因为在内网环境下
        PermitRootLogin no  不运行root用户直接登录
        Port 11544 更改访问端口号
        ListenAddress  192.168.25.130  只监听内网的IP
        Match User anoncvs     当前环境允许登录的用户
        PermitRootLogin no      是否允许root用户登录，一般不允许开
    1-2重启服务
        service sshd restart       写入命令进内存
        service sshd reload(优先)  reload是一个平滑的访问，不影响用户使用
    1-3查看连接端口
        netstat -an | grep EST