• ssh relay
  • on home server
  • login to relay server
  • from any PC
  • ssh keep alive
  • make it persistent

1. ssh relay

you want to access your home server behind a firewall or nat from outside. you must have a public server(relay server) 122.235.139.194(sh_cvmx shanghaicavm!), which both home server and outside PC can access.

1.1. on home server

homeserver~$ ssh -fN -R 10022:localhost:22 sh_cvmx@122.235.139.194 10022 is an unused port on relay server

1.2. login to relay server

ssh sh_cvmx@122.235.139.194
shanghaicavm!

check 10022 port, shoud be like this:

relayserver~$ sudo netstat -nap | grep 10022
tcp      0    0 127.0.0.1:10022          0.0.0.0:*               LISTEN      8493/sshd

1.3. from any PC

login to relay server

ssh sh_cvmx@122.235.139.194
shanghaicavm!

Then on relay server, login to home server:

relayserver~$ ssh -p 10022 cvm@localhost
cvmx@sh

1.4. ssh keep alive

# vim /etc/ssh/ssh_config
Host *
    ServerAliveInterval 60
    ServerAliveCountMax 2

sudo service ssh restart

1.5. make it persistent

1. passwordless ssh login, on home server

   ssh-keygen -t rsa -P ''
   cat ~/.ssh/id_rsa.pub | ssh root@112.74.210.173 "cat >> ~/.ssh/authorized_keys"
   

   注: 有的时候还是不能免密登录, 此时要该服务端的权限 chmod 600 authorized_keys

2. yum install autossh

3. homeserver~$ autossh -M 10985 -fN -o "PubkeyAuthentication=yes" -o "StrictHostKeyChecking=false" -o "PasswordAuthentication=no" -o "ServerAliveInterval 60" -o "ServerAliveCountMax 3" -R 112.74.210.173:11985:localhost:22 root@112.74.210.173
4. ssh root@112.74.210.173 Cavium@sh
5. ssh -p 11985 cvm@localhost cvmx@sh