Changing displayed hostname in bash prompt based on login credentials

Question

I host several domains on one server.

I would like to be able to change the displayed hostname in my bash prompt to indicate which one I picked when ssh'ing into the server.

My prompt is as follows:

\u@\h

This displays as:

user@hostname

How would I change the \h to show which domain I had logged-into (blah.net, hmm.com, etc)?

Answer 1

It turns out that ssh finds lines in ssh_config(5) by string matching, so it's OK if all the IP's are the same.

What you want, then, are

• Different lines in .ssh/config for each system, use HostName to give ssh the real host domain name
• Have three different environment variables with different prompts in them in your local environment
• Have each line in .ssh/config send a different variable using SendEnv, see man ssh_config.
• Make your prompt out of all three (two will always be null)
• Put AcceptEnv * in /etc/ssh/sshd_config and sudo kill -1 $(cat /var/run/sshd.pid)
  (AcceptEnv E1 E2 E3 should also work.)

Example.

Client .ssh/config

Host barb
        HostName deb
        SendEnv BARB

Host jane
        HostName deb
        SendEnv JANE

Host deb barb jane
        Protocol 2
        ForwardAgent yes
        Compression no

Server .bashrc

PS1='$BARB$JANE.otherstuff...'

Server /etc/ssh/sshd_config

...
AcceptEnv *

Answer 2

Do your domains all have different IPs?

If so, you can use the variable $SSH_CONNECTION once you are logged in.

If not, then it is impossible to differentiate, all the server sees is the IP address, there is no such thing as name-based ssh.

Answer 3

One way to do this could be to make entries for each of your hostnames in your local ~/.ssh/config, configured to connect to different ports on your server.

Host foo
  HostName www.foo.com
  Port 1022


Host bar
  HostName www.bar.com
  Port 2022

Then your ~/.bashrc on the server can parse the SSH_CONNECTION environment variable and pick out the port you've connected to, and change the prompt accordingly.

case $(ruby -e 'puts ENV["SSH_CONNECTION"].split[-1]') in
  1022)
    WEBHOST="www.foo.com"
  ;;
  2022)
    WEBHOST="www.bar.com"
  ;;
  *)
    WEBHOST="www.foobar.com"
  ;;
esac


PS1="\n\u@$WEBHOST \w\n$?> "

Obviously you would need ruby in your path for this, but you see what I mean.

Answer 4

You might be able to use the SendEnv directive (protocol 2 is required and sshd on the remote machine must be configured for AcceptEnv to include the name of the variable you want to use):

On the local machine:

export dest=example.com; ssh -o "SendEnv dest" username@$dest

On the remote machine, in ~/.bashrc:

PS1="...${dest}..."

Where the ellipses represent the rest of the stuff in your prompt.

If you edit /etc/ssh/sshd_config to add a variable you may have to send SIGHUP to sshd.

Answer 5

Or, if you already use bash on these domains, edit the .bashrc file to add the line:

PS1='\u@\h:\w\$ '

So that when you login and switch to bash the username and hostname are displayed.

Answer 6

What you have to do is to specify prompt (PS1) with correct hostname during connection to a server. Assuming you use ssh client on Linux machine you can do it by running command:

ssh -t username@hostname-001 "export PS1='\u@hostname-001'; bash --login"

I found this technique very useful while managing connections to many servers without proper hostname set (like in EC2 amazon default hostnames). I wrote a small bash helper function, used bash aliases and put it in .bashrc file.

function __ssh_helper {
    local user=$1
    local host=$2
    local txtgrn='\e[0;32m'
    local txtblu='\e[0;34m'
    local txtcyn='\e[0;36m'
    local txtrst='\e[0m'
    ssh -t ${user}@${host} "export PS1='[${txtcyn}\u${txtrst}@${txtgrn}${host}${txtrst} \W]\$ '; bash --login"
}

alias hostname-001.prod='__ssh_helper username hostname-001.prod'
alias hostname-002.prod='__ssh_helper username hostname-002.prod'

I used /etc/hosts file to point hostname-00(1|2).prod to ip addresses. To add new ssh connection simply: 1. add hostname to /etc/hosts file; 2. add an alias to .bashrc; 3. pick up changes by sourcing .bashrc file. Hope it helps someone :-)