Computersnyou

SSH Configuration tweaks to make your life simple

Posted on  8/24/2015

If you use ssh a lot and do login daily in many servers or virtual machines , with different usernames and different passwords , then let me show you easy way of doing that using ssh configuration file so you dont have to remember all the different IP addresses and username etc . we are going to modify ~/.ssh/config file to setup some per user based configuration .

Screen Shot 2015-08-24 at 9.40.13 pm
Screen Shot 2015-08-24 at 9.40.13 pm
  • user’s configuration file : `~/.ssh/config `
  • system-wide configuration file : `/etc/ssh/ssh_config `
  • Simple Config

    edit ~/.ssh/config file and add Host entry like displayed below , you can setup various options , like Hostname , Port and User etc .

    if ~/.ssh/config doesnt not exist , then you can create it using touch

    touch ~/.ssh/config

    Now edit ~/.ssh/config

    Host database
        HostName db.example.com
        Port 2222
        User alok

    after this simple configuration you can connect to database server by just typing ssh database .

    There are many options you can configure in your config file for example if you use different key pairs for different hosts then you can pass IdentityFile option to use that specific key.

    Host database
        HostName db.example.com
        Port 2222
        User alok
    
    Host bitbucket.com
       IdentityFile /home/myname/.ssh/private-identity
       Hostname bitbucket.com
       User alok
    
    Host github.com
      Hostname github.com
      IdentityFile /home/myname/.ssh/public-identity

    If host is behind firewall or proxy or gateway and most of the ports are blocked then you can create ssh tunnel and forward you traffic through that tunnel . for example you can forward local 3305 port to of localhos to remote 3306 port to access mysql .

    creating tunnel , manual way

    ssh -f -N -L 3305:127.0.0.1:3306 [email protected]

    or you can tweak you config file to create local tunnels easily

    Host dbtunnel
        HostName database.example.com
        LocalForward 3305 127.0.0.1:3306
        User alok

    Now you can create tunnel simply by typing .

    ssh -f -N dbtunnel

    there and many options you can pass like you can set cipher type and X11 forward like options in config file you can see full list of options here , http://linux.die.net/man/5/ssh_config .
    Use man ssh to see other ssh related manual pages .

    Host database
        HostName host.example.com
        Port 2222
        User alok
        ServerAliveInterval 120
        LogLevel FATAL

    SSH Documentation : http://linux.die.net/man/5/ssh_config


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