Setting a variable for a given SSH host

In ssh_config, one can choose to export some environment variables to the host using SendEnv.

Is there also a way to force a given value for this variable, per host? For example, would it be possible to export variable $FOO with value bar only when connecting to host example.com?

Solution 1:

You can't give a specific value for an environment variable in ssh_config, but you can certainly send the existing environment variable only to specific hosts.

Host example.com
    SendEnv FOO

To complete the chain:

FOO=bar ssh [email protected]

Finally, the remote server must have the environment variable listed in AcceptEnv in its sshd_config.

AcceptEnv FOO

Solution 2:

You can give a specific value by using SetEnv in your ~/.ssh/config, e.g.

Host *
  SetEnv FOO=bar

As per man ssh_config:

Directly specify one or more environment variables and their contents to be sent to the server. Similarly to SendEnv, the server must be prepared to accept the environment variable.

Assuming your server got the following line in /etc/ssh/sshd_config:

AcceptEnv LANG LC_* FOO

Check also: man ssh_config and man sshd_config.